FR2698422A1 - Hydraulic clutch unit for forestry drum winch - comprises disc connected to shaft motor, and sliding disc controlled by hydraulic jacks mounted in winch drum frame - Google Patents

Abstract

The clutch (7) consists of one disc (9) connected to a shaft motor (10), and a sliding disc (8) whose axial movement is controlled by hydraulic jacks (13) mounted in the flange (11) which is solid with the winch drum (3). This flange is mounted via bearings (22-24) to a bearing spindle (16) mounted on a bearing support plate (15) which is rigidly fixed to the framework of the winch. Inside this bearing spindle is a rotary fluid coupling (19) which feeds the hydraulic oil from the feed line (17) in the bearing support plate to channels in the rotating flange (21,21a) and then to the jacks. USE/ADVANTAGE - A compact hydraulic operated clutch unit for a drum winch associated with a winching cable for forestry work.

Description

 Clutch device, in particular for a forestry winch.

 The invention relates to the field of winches.

 More specifically, the invention relates to the field of clutch devices intended to equip certain winches and in particular, but not exclusively, winches for forestry use.

 Forestry winches are widely used in forestry, both during deforestation and forest maintenance, to move slaughtered or uprooted trunks from their place of cut or fall to a means of transport or a place storage.

 To facilitate their implementation on vehicles, these winches may be provided with a clutch for transmitting the driving force of these vehicles to at least one winding drum of a cable.

 Such winches with clutch device can be mounted directly on the vehicles used to transport the trunks. However, such vehicles generally have an imposing size that prevents them from being brought sufficiently close to the cutting sites so that the length of the cables mounted on said winches can allow access to the felled trunks. This is the reason why smaller vehicles, such as tractors or 4WD all-terrain vehicles, are also frequently equipped with such winches so as to be able to access areas closer to the felled trunks. at the cutting sites and to be able to tow them to a place of storage or to means of transport.

 The problem of accessibility to logging sites is particularly acute in forest areas in hilly terrain such as mountainous areas. The exploitation and maintenance of forests growing on such areas therefore have limits which can only be overcome by equipping the towing vehicles with winches with the longest possible traction cables.

However, besides the fact that these cables must have a resistance the more important that they are long, the winches to which they are connected must not exceed a certain dimensional space: in particular, they must have an overall length in agree with the dimensions of the vehicles on which they are intended to be installed in such a way that such vehicles can access unhindered sufficiently close to the cutting sites. However, the longer the towed cable by a winch, the more the drum of this winch must be large and bulky. The problem of congestion also arises with regard to the clutch system winches.

 Known in the state of the art various types of clutch winches, the principle of the clutch consisting in coupling, for example under the action of at least one piston hydraulic cylinder, at least one smooth clutch disc with at least one packed disk engaged with a motor shaft. (It will be noted that in the present description, the word "disk" will denote any element having an annular useful surface). For example, these winches may have two drums for receiving a cable mounted longitudinally on the same motor shaft, each of said drums being provided at one of its ends with a clutch device on said motor shaft. Each drum can operate independently and allow the winding of a cable of a predetermined maximum length depending on the winding capacity of the drum.This capacity is a function of the useful length of this drum, that is to say the length over which the cable can be wound. Since the overall length dimensioning of the winch must not exceed a certain limit imposed by the dimensions of the vehicles intended to accommodate it, the length of the cables wound on each drum depends on: - the section of these cables on the one hand and - the capacity and therefore the useful length of the drums, that is to say the length over which the cables can be wound, on the other hand.

 Thus, a forest winch is already known having two drums mounted longitudinally on the same drive shaft and whose clutch devices each have three fixed pistons mounted in a movable flange in translation cooperating, by means of a bearing, with a set of smooth discs. These smooth discs may, under the action of said pistons, be brought into contact with a set of friction discs engaged on the motor shaft. Such a clutch device comprises two lined disks and two smooth disks, which allows to provide four clutch surfaces for the transmission of a high traction power to said drums.

 Since the piston set of such a device is not mounted in a rotating element, the supply of hydraulic control fluid is relatively simple. However, the presence of an intermediate piece constituted by a bearing disposed between the pistons and the smooth discs in order to transmit the action of the pistons on the filled discs, has the consequence of increasing the bulk of such a device. clutch. This size is further increased by the fact that the device involves two smooth disks and two trimmed disks, whose thicknesses are superimposed and which contribute to confer the clutch device sizing width very important.

 Such a winch has the disadvantage of having a ratio: effective length of winding cables / overall length of the winch, relatively low.

 Also known in the state of the art, a forest winch also having two cable winding drums mounted longitudinally on a motor shaft, each drum being able to cooperate independently with a clutch device having a rotating flange. clutch inside which is bored a central chamber for accommodating a single piston. Such a winch is equipped at each of its ends with a bearing to take all the efforts of the winch and intended to be secured to a housing.

 The use of a rotating clutch flange makes it possible to eliminate the rolling element interposed between the pistons and the smooth disc of the recovery winch of the technique previously described. However, in order to allow the supply of hydraulic control fluid to the piston chamber, it is necessary to rotate the clutch flange on the bearing by means of a bearing whose outer ring is mounted on the fixed bearing and whose the inner ring is mounted on the rotating flange. The fluid supply of such a clutch device is then through the center of the clutch flange and requires the presence of supply means projecting outside the bearing.

 The presence of such means has the effect of encroaching on the horstout length of the winch and thus reduce the useful length of winding drums. The length of the cables that can be wound on these drums is thus limited. This disadvantage is reinforced by the fact that such a clutch device having only one piston, the smooth disc must be relatively thick.

 Finally, the existence of a bearing between the bearing and the clutch flange makes it impossible to supply the hydraulic control fluid through this bearing.

 There is therefore a need for a forestry winch, having a length not exceeding that of existing devices but allowing towing a longer cable length.

 The object of the present invention is therefore to provide a winch provided with a clutch, which may have one or two winding drums and the useful length of the drums is increased compared to existing devices of the state of the art.

 Another object of the invention is to provide a forest winch not having an overall length greater than those of winches of the state of the art.

 These objectives, as well as others which will appear hereafter are achieved according to the invention by means of a clutch device for winch, in particular for forest winch, of the type intended to couple and uncouple a drum. winding a winching cable with a motor shaft through at least one set of clutch disks comprising at least one movable disk with hydraulic coupling control by at least one hydraulic cylinder fed by a hydraulic supply circuit, each cylinder consisting of a piston sliding in a chamber bored in a clutch flange integral with said drum, said flange being rotatably mounted on a fixed bearing integral with a frame, characterized in that said bearing is extended by a spindle bearing flange forming a fixed support of said rotary flange via a first principal means of rotation, said spindle being provided with a central bore accommodating a rotary cylinder s olidaire said flange and forming an artery of said hydraulic supply circuit, said artery ensuring the junction between an inlet duct passing through said bearing and supply channels of said chambers.

 According to the invention, it is therefore possible to increase the useful winding length of the drums by equipping the forest winches with such a clutch device, since the supply of the pistons with hydraulic control fluid is integrated into the system. bearing and does not protrude outside of that as in the devices of the state of the art.

 Moreover, such a device does not involve a bearing between the smooth disc and the pistons since they are rotatably mounted in the clutch flange.

 A double space saving is thus achieved, on the one hand by the absence of such a bearing and, on the other hand, thanks to the integration of the supply means in the bearing.

 Preferably, said first main rotation means is constituted by a bearing whose outer ring is mounted on said rotary clutch flange and whose inner ring is mounted on said flange gate pin.

 Advantageously, said rotary cylinder is rotatably mounted in said bore via a second rotation means constituted by a set of two bearings. Such an arrangement makes it possible to secure the positioning of the means in said flange pin.

 Also advantageously, said inlet duct of said supply circuit is placed substantially radially to said bearing and has an inlet orifice located approximately in the periphery zone of said bearing and opens opposite said rotary flange.

 Preferably, a rotary joint is disposed between said flange pin and said cylinder. Such a seal makes it possible to proscribe leaks of hydraulic fluid at the level of the cooperation surface of the cylinder of the flange and the flange gate pin.

 Also advantageously, said clutch flange has at least three chambers symmetrically distributed in a ring, concentrically to the motor axis, and for accommodating at least three pistons, said cylinder artery opening into at least three radial channels, each of said radial channels being connected to one of said chambers housing said pistons.

 The distribution of the pistons according to a ring makes it possible to distribute the force transmitted by these on a larger surface. Winches equipped with such a set of pistons thus have a greater pulling force.

 Advantageously, said clutch flange has six chambers each accommodating a piston.

 Also advantageously, the clutch device comprises a single packed disc capable of cooperating with a single smooth disc. In this way the length of the clutch device is further reduced. Given the fact that the distribution in a ring allows the distribution of the forces transmitted by them over a larger surface of the smooth disc, the latter may have a moderate thickness, which still contributes to reducing the size of the clutch device according to the present invention.

 The invention also relates to a forestry winch characterized in that it is provided with such a clutch device. Such a winch may include two drums mounted on a common motor shaft, each of said drums being equipped at one end with a clutch device.

 The invention as well as the various advantages that it presents will be more easily understood thanks to the preferred embodiment which will follow, with reference to the drawings, in which - FIG. 1 represents a schematic front view of a forest winch having two cable winding drums, each of these drums being equipped with a clutch device according to the invention; - Figure 2 shows a longitudinal sectional view of a first clutch device of the state of the art for equipping a forest winch; - Figure 3 shows a schematic longitudinal sectional view of a second clutch device of the state of the art also intended to equip a forest winch - Figure 4 shows a longitudinal sectional view of a clutch device for forestry winch according to the present invention.

 According to FIG. 1, a forest-use winch 1 according to the invention is shown schematically from the front. This winch 1 consists essentially of a frame 2 welded housing forming inside which are arranged two drums 3,4 concentrically mounted on a single drive shaft and can operate independently.

 The winch 1 further comprises a wheel and worm gear and an electro-hydraulically controlled belt brake.

 Each of the drums 3,4 is equipped at one of its ends with an electrohydraulically controlled dry disc clutch, the clutch devices being installed in the end portions 5, 6 of the frame 2. Electrohydraulic equipment to feed these clutch devices is fully integrated with the frame 2.

 The winch shown in FIG. 1 has an overall length A of 1200 mm and a useful cable winding length B of 330 mm per drum, ie 660 mm. Such a useful length allows the winding, for each drum, 220 m of cables with a section of 16 mm or 270 m of cables with a section of 14 mm.

 The pulling force at the shaft of such a winch is 16000 daN. The hydraulic equipment integrated in the frame 2 can provide the clutch device with a pressure of 140 bar. Finally, such a winch can operate with a power supply of 12 volts or 14 volts.

 Thanks to the invention, the complete integration of the hydraulic control fluid supply means of the two clutch devices located at each end 5, 6 of the winch makes it possible to increase the useful length of the drums 3,4 and thus to allow a winding, for each of these drums, a longer cable length. Indeed, such a winch has a ratio: useful length / overall length of 660mm / 1200mm or 0.55 while forest winches of the state of the art have such a ratio not exceeding 0.46.

 Before describing in detail, an exemplary embodiment of a clutch device according to the invention, in particular forming part of the forest winch shown in Figure 1, description is made to Figures 3 and 4 of the two clutch devices for forest winches known in the state of the art.

 Referring to Figure 2, a clutch device for forest winch 51 of the state of the art is shown in longitudinal section. Such a forest winch 51 has, in a conventional manner, two drums each provided, at one of their ends, with such a clutch device and mounted on a common motor shaft. In a conventional manner, each of these drums can operate independently.

 FIG. 2 shows such a clutch device 51 mounted on frame 52 of the winch accommodating it and also partially shows one of the two drums 53 of such a winch as well as a portion of the drive shaft 54 allowing the transmission rotary motion to the drums.

 The clutch device of this winch according to the state of the art includes three pistons 55 mounted in a ring arrangement, concentrically to the motor axis 54. Figure 2 being constituted by a cross section of the device, only one of these three pistons is of course apparent. Such a clutch device also includes a set of smooth disks 56, 57 able to cooperate, under the action of the pistons 55 with a set of lined disks 58, 59 engaged with the drive shaft 54.

 The supply of hydraulic control fluid of the pistons 55 is carried out through a bearing 60 fixed to the frame 52. An intermediate piece 61 accommodating the pistons 55 is disposed between these pistons and the set of smooth disks 56, 57 so that the supply of oil causes not only the displacement in translation of the pistons but also that of the intermediate piece 61. This piece, which is mounted in abutment on the first disk 56 of the 56.57 smooth disk set allows the contacting of the smooth disks. 56.57 with the packed discs 58.59 engaged with the motor shaft 54. The rotational movement of the motor shaft 54 is thus transmitted to the drum 53 via the set of discs and the set of flexible discs In order to allow free rotation of the set of smooth discs and thus the free transmission of the rotational movement of the motor shaft 54 to the drum 53, the latter is rotatably mounted on the intermediate piece 61 by means of a roller. 62.

 As soon as the oil supply is stopped, the pistons 55 no longer force the intermediate piece 61, and therefore the smooth disks 56, 57, on the filled disks 58, 59 engaged on the motor shaft 54 and the booster 56.57 is permitted by spring means 63 connecting the set of smooth discs to the drum 53. The transmission of the rotational movement of the drive shaft 54 to the drum 53 then ceases immediately.

 As already explained above, such a clutch device 51 has a large length resulting on the one hand from the presence of the bearing 62 allowing the free rotation of the set of smooth disks 56, 57 in the engaged position, when this is in contact with the set of filled discs and secondly the use of two discs and two soft discs.

 For an overall length similar to the overall length of the winch according to the invention shown in FIG. 1, that is to say 1,128 mm, the winch of the state of the art equipped with two drums with each of the ends of which is installed such a clutch device according to Figure 2, has a useful cable winding length of 184 mm plus 364 mm (the drums are not the same length) or 548 mm and therefore a ratio: useful length / overall length of 0.48.

 According to Figure 3, another clutch device for forest winch of the prior art is shown schematically in longitudinal section. Such a clutch device 71 is also intended to equip winches having two drums mounted longitudinally on the same motor shaft, each of these drums being equipped with such a clutch device.

 The clutch device 71 shown in Figure 3 is intended to cooperate with a drive shaft 74 to allow, in the engaged position driving a drum 73.

 This device comprises a single piston 75 mounted in the center of a rotary flange 72 and along the same axis as the axis of the drive shaft 74.

 Such a clutch device further comprises a smooth disc 76 adapted to come into contact under the action of the single piston 75 with a packed disk 78 in engagement with the motor shaft 74.

 In order to allow the rotation of the flange 72 accommodating the piston 75, it is mounted in a bearing 77 intended to take all the efforts of the winch and to be secured on its peripheral portion to a not shown frame. In order to allow the free rotation of the smooth disc 76 and the clutch plate 72 accommodating the piston 75, in the engaged position, a bearing 78 organizes the rotation of said flange 72 in the bearing 77. For this purpose, the outer ring 79 of this bearing 78 is secured to the fixed bearing 77 while the inner ring of the same bearing 78 is secured to the rotary flange 72.

 In order to allow the supply of hydraulic control fluid inside the piston chamber 75 and thus allow the displacement of this piston in this chamber, the central portion of the flange 72 is bored a chamber 81 accommodating the fluid provides by supply means 82. As can be seen in Figure 3, the supply means 82 are constructed outside the bearing 77 and protrude from the clutch device.

 The operation of such a clutch device according to the state of the art is as follows.

 The fluid supply of the piston chamber 75 causes the displacement in translation thereof to push the smooth disc 76 and place it in contact with the packed disk 78 in engagement with the motor shaft 74.

This contact has the immediate effect of driving the rotation of the drum 73 as well as that of the flange 72 accommodating the piston 75. The rotation of this clutch flange is therefore authorized thanks to the bearing 78. As soon as the fluid supply of hydraulic control of the piston 75 is stopped, the smooth disc 76 is recalled by the spring means 83. The uncoupling of the smooth disc 76 of the packed disc 78 has the effect of immediately stop the transmission of the rotational movement of the drive shaft 74 to the drum 73.

 Forest winches equipped with such a clutch device have a large footprint due to the construction outside the bearing means for supplying hydraulic control fluid. Thus, a forest winch provided with two drums 73 mounted longitudinally on the same drive shaft 74 and each equipped with a clutch device 71 has, for a length of 1 200 mm, a useful cable winding length of 2 mm. times 240 mm or 480. Their useful length / overall length ratio is therefore low and does not exceed 0.4.

 The invention, with reference to FIG. 4, allows the production of a winch having a greater useful length / overall length ratio than those of the devices of the state of the art.

 With reference to FIG. 4, such a winch is provided with a clutch device 7 having a single smooth disc 8 and a single packed disc 9 in engagement with the driving shaft 10.

 This clutch device 7, which can in particular equip the winch 1 shown in Figure 1, also comprises a rotary clutch flange i1 in which are bored six chambers 12 arranged in a ring, concentrically to the axis of the motor shaft 10, and each intended to receive a piston 13. These pistons 13 are supplied with hydraulic control fluid by a hydraulic circuit 14 clutch control, shown in gray in Figure 4.

 Under the action of this hydraulic control fluid, the pistons 13 control the displacement of the smooth disc 8 and the contacting of this disc with the packed disc 9 in engagement with the motor shaft 10, so as to drive in rotation a drum 3.

 The clutch device 7 further comprises a fixed bearing 15 intended to take all the efforts of the winch and to be secured to the frame (not shown) of the winch. This bearing 15 is provided in its central part with a fixed flange pin 16 and has in its interior a conduit 17 for supplying the hydraulic control fluid to a central chamber 18 located inside the pin 16. conduit 17 is disposed substantially radially inside the bearing. It has an inlet orifice 28 located at the periphery of this bearing and opens opposite the flange 11.

 This rotary flange of the clutch It is provided in its central part with a cylinder 19 within which is bored an artery 20 and six radial channels 21. The rotary flange 11 is also provided with six radial channels 21a extending the radial channels 21 of the cylinder 19 and abutting in the chambers 12 accommodating the pistons 13. The artery 20 of the cylinder 19 thus communicates on the one hand with the central chamber 18 of the pin 16 of the bearing 15 and on the other hand with the radial channels 21 and 21a. Such a construction makes it possible to distribute the hydraulic control fluid in the six chambers 12 accommodating the pistons 13 according to the following routing: the fluid enters the conduit 17 through the orifice 28, is brought to the bearing 15 by this conduit 17 and then enters the central chamber 18 of the flange pin 16 fixed on the bearing 15. The fluid then enters the artery of the cylinder 19 of the clutch plate 11 and is distributed to the various pistons 13 by the radial channels 21, 21a.

 In order to allow free rotation of the clutch plate 11, it is rotatably mounted on the flange pin 16 of the bearing 15 by means of a main bearing 22 whose inner ring 23 is mounted on the fixed flange pin 16 and whose outer ring 24 is mounted on the rotary clutch plate 11.

 Furthermore, a set of secondary bearings 25 is mounted between the cylinder 19 and the inside of the flange pin 16, in order to secure the rotation of the cylinder 19 of the flange 11 in the flange pin 16 of the bearing 15.

 In order to avoid any flow of hydraulic fluid at the junction of the cylinder 19 of the flange 11 and the flange pin 16, a rotating joint 27 is disposed between these two elements.

 The operation of the clutch device according to the invention is as follows. Under the action of the hydraulic control fluid, the pistons 13 move the smooth disk 8 so that it comes into contact with the packed disc 9 in engagement with the motor shaft 10. This contact makes it possible to transmit the rotation from the drive shaft 10 to the clutch flange 11 and to the drum 3. The free rotation of the flange Il and the pistons 13 is made possible by the presence of the main bearing 22 allowing the rotation of the cylinder 19 of the flange 11 in the spindle Flange 16 of the bearing 15. The particular arrangement of this pin 16 around the cylinder 19 allows complete rotation of the flange without interrupting the supply of hydraulic control fluid.

 As soon as the supply of hydraulic control fluid is stopped, the pistons 13 stop exerting a force against the disc 8, the return of which is authorized by spring means 26. The uncoupling of the smooth disc 8 of the packed disk 9 causes the Immediate stop of the drum 3.

 The integration of the supply means of the hydraulic control fluid in the bearing 15 has the advantage of allowing a reduction in the width dimensioning of the clutch device according to the invention. Thus, it is possible to obtain winches whose drums have a much greater useful length than drums of the state of the art and thus allow the winding of longer cable length.

 Referring to the table below, three forest winches each having two cable winding drums and each drum is equipped with a clutch device, were tested.

 The forest winch referred to in Example 1 of this table is equipped with two clutch devices of the state of the art (one for each drum) in accordance with that shown in Figure 2.

 The forest winch referred to in Example 2 is equipped with clutch devices according to the state of the art in accordance with that shown in FIG.

 Finally, the forest winch referred to in Example 3 is equipped with clutch devices according to the invention according to Figure 4, and corresponds to the winch shown in Figure 1.

According to this table: Lht represents the overall length of the winch,
Lu represents the cumulative useful length for the two drums of the tested winch; Lc16 represents the cable length of a 16 mm section that can be wound on all two cables.

<tb> Example <SEP> Lht <SEP> Iii <SEP> Lcl6 <SEP> LhtLu <SEP>
<tb><SEP> mm <SEP> mm <SEP><SEP> m
<tb><SEP> 1 <SEP> 1200 <SEP> 480 <SEP> 160 <SEP> 0.40
<tb><SEP> 2 <SEP> 1128 <SEP> 548 <SEP> 120 <SEP> 0.48
<tb><SEP> 3 <SEP> 1200 <SEP> 660 <SEP> 220 <SEP> 0.55
<Tb>

 It will be seen that a winch with two drums of the type of that represented in FIG. 1, provided with a clutch device according to FIG. 4, allows the winding of a length of cables greater than 37.5% to 50.degree. % to those authorized by prior art forestry winches.

 Such an advantage is a significant advance since it allows users of such winches to access tree cutting sites 60 m away. Such a gain contributes to significantly increasing the productivity of these users.

 The exemplary embodiment described here is not intended to reduce the scope of the invention. In particular, it will be entirely possible to equip forestry winches with only one drum of such a clutch device. It may also be possible to provide the clutch flange with a different number of pistons. Of course, it will also be possible to equip other types of winches than forestry winches of the clutch device claimed without departing from the scope of the invention.

Claims (10)

1. Clutch device (7) for a winch (1), in particular for a forest winch, of the type intended to couple and uncouple a winding drum (3) of a winching rope with a motor shaft (10) to through at least one set of clutch discs (8, 9) comprising at least one hydraulic coupling controlled movable disk (8) by at least one hydraulic cylinder fed by a hydraulic supply circuit, each cylinder consisting of a piston (13) sliding in a chamber (12) reamed in a clutch flange (11) integral with said drum (3), said flange (11) being rotatably mounted on a fixed bearing (15) integral with a frame characterized in that said bearing (15) is extended by a flange pin (16) forming a fixed support of said rotatable flange (11) via a first principal means of rotation, said spindle (16) being provided with a central bore accommodating a rotary cylinder (19) integral with said flange (11) and forming an artery (20) of said hydraulic supply circuit, said artery (20) providing a junction between an inlet duct (17) passing through said bearing and supply ducts (21, 21 a) of said chambers (12) . 2. clutch device (7) according to claim 1 characterized in that said first main means of rotation is constituted by a bearing (22), the outer ring (24) is mounted on said rotary clutch flange (11). and whose inner ring (23) is mounted on said flange pin (16). 3. clutch device (7) according to one of claims 1 or 2 characterized in that said rotary cylinder (19) is rotatably mounted in said bore of said pin (16) via a second means of rotation constituted by a set of two bearings (25). 4. clutch device (7) according to one of claims 1 to 3 characterized in that said inlet duct (17) of said supply circuit is placed substantially radially to said bearing (11) and has an orifice of an inlet located approximately in the periphery zone of said bearing (11) and opening opposite said rotary flange (11). 5. Clutch device (7) according rune claims 1 to 4 characterized in that it comprises a rotary joint (27) disposed between said flange pin and said cylinder sealing the hydraulic fluid between these two elements. 6. Clutch device (7) according to one of claims 1 to 5 characterized in that said clutch flange (11) has at least three chambers (12) symmetrically distributed in a ring, concentrically to the axis of the clutch. motor shaft (10) and for accommodating at least three pistons (13), said artery (20) of the cylinder (19) opening into at least three radial channels (21,21a), each of said radial channels (21,21a ) being connected to one of said chambers (12).  7. clutch device (7) according to claim 6 characterized in that said clutch plate (11) has six chambers (12) each accommodating a piston (13). 8. clutch device (7) according to one of claims 1 to 7 characterized in that it comprises a single mobile disc (8). 9. Forestry winch (1) characterized in that it is provided with a clutch device (7) according to one of claims 1 to 8. 10. Forestry winch according to claim 9 characterized in that it comprises two drums (3,4) mounted on a common drive shaft (10), each of said drums (3,4) being equipped at one of its ends with a clutch device (7) according to one of claims 1 to 8.