FR2475669A1 - DEVICE FOR TURNING ON A DRIVE MEMBER - Google Patents

Abstract

THE PRESENT INVENTION CONCERNS A CHAIN TENSIONING DEVICE, WHICH INCLUDES TWO ARMS 2, 3 SWIVEL TOGETHER AND SOLICITED SO AS TO BE FAR FROM ONE ANOTHER SO THAT ARM 3 APPLIES A TENSIONING FORCE TO A CHAIN BY MEANS OF A 5 CAM BLOCK LOADED BY SPRING. AS AN ALTERNATIVE, A SPRING LOADED BLOCK CAN BE USED WITH CONNECTING RODS COUPLED BETWEEN THE BLOCK AND THE ARMS. A DISC 9 AND ROD 8 ARRANGEMENT IS PROVIDED WHICH MAKES AVOIDING A RETURN MOVEMENT OF THE LOADED BLOCK BY SPRING AND THEREFORE THE DECLINE OF THE ARM 3 UNDER THE EFFECT OF CHAIN LOAD INVERSIONS.

Description

The present invention relates to tensioning devices for

endless control devices such as

only chains and belts.

  A particular tensioning device, constructed according to the present invention, comprises a pivoting arm, an actuator slidably mounted on a rod, a spring means urging the actuator along the rod, in one direction, the arm being caused to rotate in the direction

  of a power-up in response to a movement of the ac-

  actuator in said direction biased by spring, and a hooking disc mounted on the rod and capable of tilting so as to become jammed on the rod-in response to the return movement of the actuator despite the biasing of the spring along the rod, as would be caused by the back pivoting movement of the arm, which inhibits the

  pivoting movement of the actuator and by con-

  sequence the backward pivoting movement of the arm.

  The actuator can be in the form of a cam block

  which is stressed by a compression spring in a di-

  rection, so as to exert a wedge effect on the pivoted arm. As a variant, a compression spring can be used to bias the actuator in the axial direction, and the actuator can be coupled to the arm having pivoted by 2.

  connecting rods which transform the axial movement of the

  holder in angular movement of the arm about its axis

pivot, and vice versa.

  The present invention will be well understood during the

  following description made in conjunction with the drawings below

joints in which:

  Figure 1 is a plan view, partly in section.

  eg a tensioning device; Figure 2 is an end elevational view of the tensioning device; Figure 3 is a sectional side elevational view along the line II-II of Figure 2; Figure 4 is a side elevational view in section of another embodiment of the tensioning device; Figure 5 is a side elevation view of

  this other embodiment of the tensioning device

  sion, directly energizing a chain link; FIG. 6 is a side elevation view of this other embodiment of the tensioning device, carrying out the tensioning of a chain aid; Figure 7 is a side elevational view of a third embodiment of the tensioning device Figure 8 is a sectional view taken along line VIII-VIII of Figure 7; Figure 9 is an end elevational view of this third embodiment of the tensioning device; FIG. 10 is a side view, partly in section,

  the this third embodiment of putting under-

  voltage; Figure It is a side elevation view of

  this third power-up device, direct-

  energized a chain control; Figure 12 is a side elevation view

  of another version of the third embodiment of the provision

  tensioning device, represented during a direct tensioning of a chain control; and 3. Figure 13 is a side elevational view of a

  another version of the fig.

  res 7 to 11, when used to energize

  a longer chain order.

  As shown in Figures 1 to 4, a tensioning device 1 comprises a pair of upper arms

  2 and lower 3, generally channel-shaped, which pivots

  try together at one of their ends around an axis of

pivot 4.

  The arms 2 and 3 pivot to be spaced from each other by means of a cam block 5 which is mounted so as to make the lower arm 2 slide longitudinally and is biased by a compression spring 6 towards the

  pivoting ends of the arms.

  Block 5 has an opening at 7 and is mounted

  at this opening on a guide rod 8 which extends lon-

  gitudinally to the lower arm 2. The compression spring

  sion 6 is mounted around the rod 8 and enters the block so as to sit at its inner end against a hooking disc 9 also mounted on this rod. So,

  the spring 6 applies a biasing force by the

from disc 9 to block 5.

  The outer end of the spring 6 sits on a support flange 10, which is in one piece with the

  lower arm 2 and which supports in sliding an end

  Outer half of the guide rod 8. The guide rod 8 is mounted at its inner end by sliding on an arm member 11 which is not axially movable and has an enlarged head 12 which prevents its removal. The member 11 has the form of a channel support with its flanges 13 pivotally mounted around the axis 4, its core 14 receiving the rod

guidance 8.

  If 'the energizing device 1 is to be

  used to energize a distribution chain

  engine, the lower arm 2 will be positioned by its

  mounting openings 15 relative to the drive assembly

  chain and motor drive. The upper arm 3 will pivot 4. then to move away from the lower arm 2 under the effect of

  block of block 5 biased by spring. The upper arm 3 carries

  te an S heel which is riveted on it and which comes direct-

  in contact with the distribution chain so as to energize it. With the previous construction, the wedge effect

  of block 5 will be regular and progressive, the block being able to slide

  ser freely along the guide rod 8, under the ground

  licitation due to compression spring 6, through

  diary of the disc 9, and being guided by the base of the block 5 in

  sliding contact with the base plate 16 of the lower arm

laughing 2.

  The tensioning device 1 exerts a

  resistance to chain load reversals. In such-

  the conditions, the return movement of the block 5 against the stress of the compression spring 6 and the subsequent collapse of the upper pivot arm 3 is avoided by the disc 9 which gets stuck on the guide rod 8. At this time, the block 5, the disc 9 and the guide rod 8 can only move as one and the same, and the contact of the head 12 of the guide rod with the core 14 of the

  arm l determines the extent to which the guide rod

  ge and therefore the block can move backwards

re.

  Note that when the disc 9 is perpendicular to the

  re to the guide rod 8, it does not get stuck against the rod, and a relative longitudinal movement between the two elements can occur. This situation occurs when the block is biased forward, the compression spring 6

  acting through the disc 9, so as to act com-

  hold me on the upper arm 3 to open it. Is the

  moment when the disc 9 rocks relative to the guide rod

  ge 8 that it will get stuck against it, and this situation

  originates from the fact that the disc is placed in a hollow

  ment 17 of the block 5,1 'recess having an inclined front face

  18. Consequently, when block 5 tends to move

  cer backwards along the guide rod 8, its face 5. 18 causes the disc 9 to tilt to cause it to get stuck on

the guide rod.

  To avoid overloading the T chain, a certain

  lost movement is provided in the tensioning device

  sion 1 by the fact that the guide rod 8 is free of cou-

  smooth in the core 14 of the member 11 according to a pre-

  determined limited which is a function of interstice 1 sepa-

  rant the head 12 of the guide rod of the pivot shaft of the arm 3. Thus, although the block 5 and the disc 9 can slide freely on the guide rod 8 when they are biased forward by the compression spring 6, there will be a tendency because of friction that the rod 8 also moves forward and slides inside the core 14 according to the distance g at the time when the head 12 of the rod guide will abut against the pivot shaft 4, and the guide rod will be prevented from moving further inward. Consequently, in the case of a reversal of load having the effect of a rearward displacement of the block s and consequently a tilting and jamming of the disc 9. Against the rod 8, since the rod 8 has previously moved forward and therefore its head has moved away from the core 14 of the support, there is a possibility of rearward movement of the guide rod until its head 12 abuts the core 14. Thus, although the block 5, the disc 9 and the rod 8 can only move backwards as one and the same assembly, they will effect this movement within the limit imposed by the value of

the gap g.

  As will be noted, thanks to an appropriate adaptation

  property of the construction, the value of the gap 9 can

  be modified, and therefore the importance of the movement per-

  stem 8 can likewise be modified according to the operating characteristics of the engine on which the

  tensioning device must be fitted.

  The tensioning device can be blocked

  in the spring loaded condition for shipping and release

  rusty after installation. For this purpose, a locking pin 19 6. is removably inserted in the drilled cores 2a of the arm 2 in the movement path of the block 5. The pin 19 can also be used when the tensioning device

  must be disassembled for repair or replacement.

  The disc 9 is provided with a pair of radial legs 20 extending in an opposite direction, which as shown in FIG. 1, protrude outside the block 5. To release the tensioning device 1 from its blocked state with spring load in FIG. 3,

  just insert a screwdriver (not shown) into the es

  pace 21 between the upper 2 and lower 3 arms, then turn it clockwise (direction seen in this figure). To block the tensioning device 1 in its state of charge by spring, a tensile force is applied by a suitable tool to the exposed tabs 20 so as to straighten the disc and pull the block 5 backwards despite the stress of the compression spring 6 and the locking pin 19 inserted in the arm

lower 2.

  The upper and lower arms are preferably stamped steel parts. The block is preferably made of a suitable synthetic plastic material. The guide rod and the disc can be made of metal and can be hardened so

to resist wear.

  The variant of the tensioning device lA

  of Figure 4 has parts similar to the first arrangement

  voltage, which are indicated by

  same references and the description will relate only to the diff-

construction fences.

  One of these differences is that the end of the spring 6 bears against a support plate 10a which is

  slidingly mounted on the base plate 16 of the lower arm

  laughing and which is also slidably mounted on the

  guide ge 8 and held thereon against the action of the spring by a holding member with lob attachment. Instead of the inner end of the guide rod having a head

  enlarged, another retaining member with attachment 12a is pre-

  seen to determine the extent of movement of the rod backwards, the outer outer face of the rod when it is in contact with the pivot of the arm limiting movement forward. In addition, a ring 4a is used instead

  a pivot pin, and a standard bolt (not shown

  felt) went through the ring and would be fixed by a nut

  so as to hold the arms 2 and 3 and the member 11 together.

  The tensioning device 1A can also be locked in its state of charge by spring. For this purpose, the top of the block 5 has a notch at 22, and the upper arm 3 comprises an integral tab 23. When the tab 23 is engaged in the notch 22, the bias of the compression spring 6, acting on the block 5, will have the effect of angularly blocking the upper arm 3 relative to the lower arm 2, as shown in

  figure 4. Therefore, it is the spring load itself

  same which serves to block the tensioning device

  in its state of charge by spring.

  The heel S of the peat tensioning device

  be made of rubber and be mounted directly on the upper arm

  laughing 3. As seen in figure 5, the heel S is direct

  tely in contact with the distribution chain T, which has

  to turn it on. Alternatively, as re-

  presented in FIG. 6, the heel could be omitted, and the upper arm 3 used to indirectly apply tension to the chain T by contact with a pivoting guide strip G which would itself be in contact with the chain, as would be suitable in the case of a chain order with centers

separated by a long distance.

  The energizing device 1 could natu-

  actually be used, if necessary after adjusting the

  as shown in Figures 5 and 6.

  The two tensioning devices described

  previously included a pair of arms that swivel in-

  seems at one end and are being asked to be spread

  each other by means of a spring loaded block in

  the direction of the pivot so as to exert a wedge action in

  be both arms. The tensioning device which is

  8. ra now described does not use the wedge effect

  of a block loaded by ressDrt to request a pivoted arm

  both in tensioning engagement with a control unit

  dragging, but incorporates an organ which is charged by res-

  comes out to move it away from the pivot end of such -

  arm and which acts through a mo yen of biellet-

  swivel on the arm to rotate it in the direction

  power up. The embodiment in "biellet-

  tes "of the energizing device is designed, like this

  la apparaltra, to give the device the possibility of

  Have resistance to charge reversals in gold

  drive shaft energized and avoid overloading

age of this organ.

  As shown in Figures 7 to 10, a tensioning device 24 comprises a pair of upper and lower arms 25 and 26, respectively, pivoting together at one end around a shaft 27. An intermediate arm 28 is pivotally mounted around from shaft 27 and supports a

  rod 29 which extends generally parallel to the arm

  25, the rod 29 has an enlarged head 30 which engages at the rear of an abutment flange 31 of the arm 28 and

  is distant by a distance g from the shaft 27. A block 32 comprises

  carries an opening allowing it to be slidably mounted on the rod 29, and is urged to move away from the shaft 27 by a compression spring 33. The spring 33 is mounted around the rod 29 so as to come into contact with a end of the abutment flange 31 and to extend at its other end in the opening zone 34 of the block 32 so as to come into contact with a latching disc 35 mounted in a transverse recess 36 of the block. Finally, two links 37 are coupled between the block 32 and the upper arm 26

  so as to rotate this arm relative to the lower arm

  laughing 25 while the block is stressed along the rod

  29 by spring 33, 1 equel acts on it by means of

  disc 35. The links 37 are connected to the block 32 and to the upper arm 26 by pivot axes

38 and 39, respectively.

  9. When the tensioning device 24 is used to tension the timing chain of an engine, the lower arm 25 is mounted on the engine and is fixed in position. The upper arm 26 then rotates around the pivot axis 27 relative to the lower arm 25 under the bias of the spring 33 which biases, via the disc 35, the block 32 along the rod

  29, and the block acts at sn.bur sr the links 37 to move

  cer their lower end forward and exercise as well

  a moment of rotation on the upper arm. The upper arm

  laughter 26 may include a heel having the shape of a friction face 40, directly molded on it and produced by

  for example rubber or nylon material. As depicted

  felt in FIG. 11, the friction face 40 is directly

  in contact with the distribution chain T, which has the effect of-

to turn it on.

  As will be noted, the load of the spring

  believes with the extension of the spring 33. However, the more the block

  32 moves along the rod 29 under the effect of stress

  tation of the spring, the more the links 37 are oriented vertically; therefore, the greater the vertical component of the biasing force which has the effect of

  rotate the upper arm 26. Consequently, the present

  The construction allows a degree of compensation for the dimi-

  progressive reduction of the spring load, allowing

  rotate the upper arm 26 and thus put under tension

  The distribution chain T. The construction of the tensioning device

  24 also provides resistance to charge reversals

  Age of the T chain. First of all, any tendency of the upper arm

  laughing 26 to collapse for a sudden reversal of the movement

  ment of the chain will give rise to a vertical force component acting via the links 37 on the block 32, thus causing the blocking of the block against the rod 29. In addition, the recess 36 of the block has its front face 41 inclined, so that, during the return of the block 32 along the rod 29 against the biasing of the spring 33, this 10. face will cause the disc 35 to tilt relative to the rod and will jam against it, which will have the effect avoid the

  continuation of the return movement of the block.

  Indeed, at that time, block 32, the dis-

  that 35 and the rod 29 can only move as one

  together. As a result of the gap g between the widened end

  rod 30 and shaft 27, a limited degree of movement

  backwards is available for the rod and therefore

  quent for the set cited above. As a result, a certain lost movement is provided in the tensioning device which serves to avoid overloading the chain T, the value of the gap _ determining the extent of this lost movement and therefore the degree with which the upper arm 26 can collapse under the effect of the load

chain.

  When the overload conditions have disappeared, the action of the spring on the disc 35 will cause the disc to tilt upwards, thus releasing it from its friction-blocking contact with the rod 29, and will cause the stress.

  of block 32 along the rod which will result in the pivot

  ment by the links 37 of the upper arm 26 outwardly

  laughing. As a result of friction, the rod 29 will be brought forward until its end 30 is again in contact with the abutment flange 31, so that there is again a certain degree of retraction of the arm higher 26,

  determined by the value of the gap g.

  The disc 35 and the block 32 will have a shape which will allow the disc to tilt upwards by means of an appropriate tool and to release it, at the opportune moment of its

blocking state.

  The rods 37 act as a lever and, consequently,

  quent, by changing their length, different lever arms

  can be imposed on the outer arm 26 for the same tension

  compression spring. Thus, lighter springs

  gers could be used by increasing the length of the

  connecting rods 37. The variation in the length of the connecting rods

  also puts to make different remedies for it. take into account the wear of the chain. Here again, the length of the chain increasing, the length of the upper arm 26 can also be increased, in which case the links 37, acting as supports, would be lengthened so as to come to support the arm near its free end.

  It is not essential that there is an arm

  25, and FIG. 12 represents a tensioning device 24A not having this arm. The function of a

  lower arm is to act on the support surface, on which

  the block 32 can slide and by means of mounting the device

  positive power-up on the motor. The first function can be ensured by an appropriate shaping of the structure E of the engine, or for example by a flange of angle support fixed to this structure. The second function can be fulfilled by mounting the ends of the pivot shaft 27 in a one-piece support means with the

  motor structure or attached thereto.

  The upper arm 26 could also be omitted

  in the case of a long T chain as shown

  felt in FIG. 13. In this case, the tensioning device 24B is mounted near the free end of a guide strip G which pivots in P. This device is similar to the tensioning device in FIGS. 7 to 10, except that the links 37, instead of pivoting on the upper arm,

  pivot at 39 directly on the guide strip G itself

  even, which has tabs 42 for this purpose.

  Alternatively, in the tensioning device

  sion 24 of Figures 7 to 10, the upper arm 26 could abut against the guide strip G, so that the arm

  pivoting outward, it will rotate the guide strip

  dage to bring it into contact with the chain T and put it

under pressure.

  Alternatively, the lower arm could be shaped to wrap around the engine block rather than having the shape of a channel, as shown. The intermediate arm could constitute a block of suitable shape obtained by molding or by casting. The various components 12.

  could be fabricated in the same way that their counter

  part in the applications mentioned above.

  When the intermediate arm constitutes a block,

  the lost movement made available to the guide rod

  ge could be provided by the rod whose head is enga-

  lying in an elongated slot in the block, the long

  slit width determining the degree of movement lost.

  The present invention is not limited to the examples

  ples of realization which have just been described, it is on the contrary susceptible of variants and modifications which

will appear to those skilled in the art.

13.

Claims (25)

  1 - Tensioning device for an endless drive member, characterized in that it comprises a pivoting arm, a lifting device slidingly mounted on a rod, a spring means urging the actuator in a direction along the rod , the arm being brought to pivot   in the direction of energizing in response to movement   spring loaded by the actuator in said direction   tion, and a hooking disc mounted on the rod and capable of tilting so as to become jammed on the latter in response to the return movement of the actuator despite the biasing of the spring along the rod, as it would be caused during the pivoting return movement of the arm, whereby there is inhibition of the return movement of the actuator and by   consequence of the pivoting movement of the arm.   2 - Tensioning device according to the resale   dication 1, characterized in that it comprises means allowing-   both a limited stroke of axial displacement of the rod so as to allow a limited stroke of the return movement   of the actuator when the disc tilts to come into wedge   cer against the rod and therefore a limited degree of slackness   pivot arm return.   3 - Tensioning device according to the resale   dication 2, characterized in that the actuator has the shape of a cam block which when it is biased by the spring means in said direction exerts a wedge effect on the pivoting arm so as to pivot the arm in meaning power up.   4 - Tensioning device according to the resale   dication 3, characterized in that the spring means is a   compression spring mounted around the rod and stressed   both the actuator toward the arm pivot.   - Tensioning device according to claim 4, characterized in that the actuator comprises an inclined face contiguous to the disc so as to tilt it so as to cause it to jam against the   rod in response to the actuator return movement. 14.   6 - Tensioning device according to the resale   dication 5, characterized in that the compression spring   subjects the actuator to its action of solicitation by the disc.   7 - Tensioning device according to claim 6, characterized in that the disc is placed in a recess of the actuator, the inclined face defining a wall of the recess, the compression spring extending   in the opposite wall of the recess so as to subject di-   the disc to its action of solicitation and by cons sequence the actuator.   8 - Tensioning device according to one of the   Claims 3 to 7, characterized in that it comprises a   arm member mounted on a pivot shaft and slidingly supporting an inner end of the rod, the rod   comprising a stop means and cooperating with the pi-   vote and the arm organ, as a result of which they consti-   together kill the motion-limiting means of the ti-   ge which allows a limited stroke of the axial displacement of the rod.   9 - Tensioning device according to the resale   dication 8, characterized in that the swivel arm is also   mounted on the pivot shaft so that it can pivot   ter in the direction of energization and return to back.   - Tensioning device according to the resale   dication 9, characterized in that it comprises a second arm comprising a means making it possible to mount the device   energized on a support, the second arm being equally   mounted on the pivot shaft, the cam block being supported on the second arm when it exerts its wedge effect on the swivel arm.   11 - Tensioning device according to the resale   dication 10, characterized in that it comprises a bu-   tee in one piece with the second arm, and against which the spring means reacts when it subjects the actuator to its   stressing effect, this stop member supporting in 15.   smoothing an outer end of the rod.   12 - belon tensioning device of claim 10, characterized in that it comprises a member   bearing supported sliding on the second arm and sup-   itself carrying a sliding outer end of the rod, the spring means reacting against this member   stop when it subjects the actuator to its stressing effect   tion. 13 - Tensioning device according to one   claims 10 to 12, characterized in that it comprises   an unlockable blocking means for blocking the arm   pivot in the state where it is loaded by spring.   14 - Tensioning device according to the resale   dication 13, characterized in that the blocking means comprises   an axis removably positioned in the arm direction through   towards the movement path requested by spring of the ac-   holder. - Tensioning device according to one   of claims 1 to 14, characterized in that it comprises   a means of legs on the disc, with which comes in con-   tact a tool, thanks to which the disc can be straightened to   from its inclined position so as to allow movement   pivot arm return.   16 - Tensioning device according to one   of claims 1 to 15, characterized in that the pivot arm   both wear a heel, which when in use with the tensioning device comes directly into contact with the endless drive member to tension it. 17 - Tensioning device according to one   of claims 1 to 15, characterized in that the swing arm   voting, used in the tensioning device, ap-   indirectly applies a tensioning force to the organ-   endless drive by direct contact with a pivoting guide strip which is directly in contact with the drive member.   18 - Tensioning device according to the re-   16. vendication 2, characterized in that it comprises a link means coupled between the actuator and the pivoting arm, so as to transform an axial displacement of the actuator   in pivoting movement of the arm, and vice versa.   19 - Tensioning device according to claim 18, characterized in that the spring means is   a compression spring mounted around the rod and stressed   both the actuator to move it away from the pivot shaft of the arm.   20 - Device for energizing according to the   vendication 19, characterized in that the actuator has an inclined face contiguous to the disc so as to tilt the disc to cause it to jam against the   rod in response to the actuator return movement.   21 - Device for energizing according to the   vendication 20, characterized in that the compression spring   sion subjects the actuator to its stressing effect via the disc. '   22 - Device for energizing according to re-   vendication 21, characterized in that the disc is placed in a recess of the actuator, the inclined face defining   a wall of the recess, the compression spring extends   in the opposite wall of the recess to apply its   solicitation directly to the disc and therefore to the ac- holder.   23 - Tensioning device according to one   claims 18 to 22, characterized in that it comprises   an arm member mounted on a pivot shaft and sup-   slidingly carrying an inner end of the rod, the rod comprising a stop means cooperating with the pivot shaft and with the arm member so as to together constitute the movement limitation means allowing a   limited stroke of axial displacement of the rod.   24 - Device for energizing according to the   vendication 23, characterized in that the spring means is   mounted between the arm member and the disc.   - Device for energizing according to the re-   17. vendication 23, or claim 24, characterized in that the pivoting arm is also mounted on the pivoting shaft so as to be able to pivot in the directions of placing   energized and back again.   26 - Tensioning device according to claim 25, characterized in that it comprises a second arm comprising a means making it possible to mount the tensioning device on a support, the second arm also being mounted on the pivot shaft , the actuator being   slidably mounted on the second arm.   27 - Tensioning device according to one   from claims 18 to 26, characterized in that the arm of   pivoting carries a heel which, used in the tensioning device, comes directly into contact with the member   endless drive to turn it on.   28 - Tensioning device, according to one   claims 23 or 24, characterized in that the arm   swivel has its pivot axis distant from the swivel shaft   and forms a guide strip which, when used with the tensioning device, applies a setting force   energized directly to the endless drive.   29 - Device for energizing according to re-   vendication 28, characterized in that it comprises a second arm comprising a means for mounting the tensioning device on a support, the second arm also being mounted on the pivot shaft, the actuator being   slidably mounted on the second arm.   - Tensioning device according to one   claims 18 to 26, characterized in that the arm   swivel used with the tensioning device ap-   indirectly applies a tensioning force to the organ-   endless drive by coming into direct contact with a pivoting guide strip which itself comes directly   encootact with the drive member.   31 - Tensioning device for an endless drive member, characterized in that it comprises a   swivel arm, a cam block supported to move axially   18. Also, a compression spring biasing the block in   an axial direction, which allows the block to exert an ef-   f and shim on the pivoting arm so as to pivot the arm in the direction of tensioning, and a means for inhibiting the axial displacement back despite the stress of the compression spring so as to inhibit movement pivoting back from the arm, the inhibiting means-comprising a rod and a disc locking means operating in cooperation. 32 - Tensioning device for an endless drive member, characterized in that it comprises a   swivel arm, a supported actuator to move axially   Lement, a compression spring biasing the actuator in an axial direction, and a link means coupled between the actuator and the pivoting arm, so as to exert a pivoting force on the arm in response to the movement of   the spring loaded actuator.   33 - Tensioning device according to the resale   dication 32, characterized in that it comprises a rod and a hooking disc operating in cooperation to inhibit the axial movement of return of the actuator despite the spring biasing effect so as to inhibit movement pivot arm return.