FR2790812A1 - DIRECTIONAL VALVE WITH TRIP THRESHOLD AND DEVICE PROVIDED WITH SUCH A VALVE - Google Patents

Abstract

Directional valve with tripping threshold (101) comprising a stepped passage (111, 112) having at input an upstream passage (111) of small section opening into the upstream chamber (A) and a downstream passage (112) of large diameter opening into the downstream chamber (B). These two passages of different diameters forming between them a shoulder (113) into which the upstream passage (111) emerges, forming therein the valve seat (114) with which a closure member (115 ). A constricted passage (110) connects the interior of the valve (1), downstream of the seat (14) to the downstream chamber, the closure member (115) is magnetic and a magnet (116) is provided at the level of the valve seat (114) to attract the shutter member (115) against the valve seat.

Description

The present invention relates to a direct valve

  tional trigger threshold comprising: - a stepped passage having as input an upstream passage of small section opening into the upstream chamber and a downstream passage of large diameter opening into the downstream chamber, these two passages of different diameters forming between them a shoulder in which opens the upstream passage by producing the valve seat with which a shutter member cooperates, - the throttled passage connecting the interior of the valve, downstream

from the seat to the downstream chamber.

  There are already known directional valves with a triggering threshold, intended in particular to equip safety stops.

  doors of motor vehicles (FR 97 12 946). Such cla-

  pets have the function of opening when they are subjected to a pressure difference greater than a fixed threshold and which corresponds to their direction of operation; they close again when this pressure difference disappears. In the case of a door stop, this means that the valve opens when the door is pushed with a force greater than the threshold in the direction which corresponds to the opening of the valve and the valve closes as soon as the force disappears opening

  applied to the door and having generated the pressure difference

on both sides of the valve.

  Such a valve is shown schematically.

  as in Figure 1, only outside of its application.

  The valve 1 is intended to release the passage 10 connecting the chamber A (in which the hypothesis reigns

  highest pressure) to chamber B, when the difference

  between the two pressures exceeds the trigger threshold

of the valve.

  The valve 1 comprises a stepped passage formed in the body 2 and consisting at the inlet, on the side of the chamber A, of a passage of small section 11 and on the other side, opening into the chamber B, of a passage of large section 12. These passages form between them a shoulder 13 in which the passage of small section 11 delimits a valve seat 14. The valve is closed by a ball-shaped closure member. This shutter member is housed inside the passage of large section 12 in a sleeve 16 with which it is in sealed contact. This sheath is

  itself sealed in passage 12.

  A spring 17 is pressed against the shutter member 15. By its other end, the spring 17 is supported on a drilled screw 18 provided with a bore 19 which passes through it completely. This screw 18 is screwed into the tapped part of the passage of large section 12 to compress the spring 17 in a tared manner fixing the triggering threshold

of the valve.

  The sheath 16 clears the strangled passage 10

as shown.

  The operation of this valve 1 is as follows: initially, by assumption, the pressure of the fluid in the two chambers A, B is identical. The piston is in equilibrium

  and the valve is closed. Its shutter member 15 is applied

  qué by the spring 17 against its seat 14.

  For example, it is assumed that the pressure of the fluid in the chamber A increases and that of the fluid in the

room B decreases.

  The difference between the two pressures is exerted through

  towards the passage of small section 11 on the part of the sealing member 15 exposed in the passage 11. When the product of this pressure (pressure difference) and the exposed surface is equal to or slightly greater than the closing force exerted by the spring 17 on the shutter member 15, the latter lifts from its seat 14. As soon as

  opening, the pressure difference is no longer exerted only

  slowly on the small surface of the obturation member 15 but on the whole side thereof exposed to this fluid from the chamber

  A. In fact, the entire surface of the shutter member 15 if-

  killed on the side of chamber A is subjected to pressure

  in the chamber A and the entire surface of the closure member 15 facing the chamber B is subjected to the pressure of the fluid prevailing in this chamber B via the passage 19 passing through the nut 18. To maintain the shutter member 15 in the open position, a pressure difference much smaller than that necessary for the initial release of the valve is sufficient, since this pressure difference no longer applies to the small surface of the member shutter but practically over the entire section of the passage 12. The drawback of the known valve lies in the

  threshold operation which is not sufficiently accentuated.

  Indeed, the ball-shaped shutter member which seals

  the fluid inlet is pushed by a spring.

  However, the restoring force developed by the spring is propor-

  tional movement of the ball. This means that the more the valve is open, the more the spring retains the ball, which creates very large pressure drops along a

  fluid stream. This does not provide a trigger

  net at the time of the threshold, which is explained by the

  gures 2A, 2B, one showing the ideal case, the other the case

  convenient. On the abscissa, the two figures represent a

  linear or angular and ordinate placement, the force of

valve retainer.

  Figure 2A shows that there is a sudden drop between level F1 and level F2 of force F on the way

  from the abscissa point aO. This is the theoretical situation

that, wanted.

  Figure 2B shows the practical situation. The passage between level F1 and level F3 does not take place suddenly at the abscissa point aO but begins at this time to end at the abscissa point ai, which corresponds to a non-ideal operation since the triggering threshold

is not clearly marked.

  The object of the present invention is to remedy

  these drawbacks and proposes to create a directional valve

  trigger threshold, the threshold effect of which is clear-

strongly accentuated.

  To this end, the invention relates to a valve

  rectionnel of the type defined above, characterized in that: - the shutter member is magnetic and

  - a magnet is provided at the valve seat for atti-

  rer the shutter member against the valve seat.

  As the magnetic attraction force applied to the closure member decreases as a function of the inverse of the square of the distance between the closure member and the element

  magnetic, as soon as the shutter member is slightly

  lifted from its seat, the restraining or pulling force of

  the magnetic element very quickly becomes extremely weak

corn.

  This force is in no way supplemented or replaced

  created by a possible return force acting on the shutter member because the return spring is simply intended

  to repel it, in the absence of other external forces,

  res, against the valve seat without being sized for the

  press against the seat and create the corresponding holding force

  laying on the opening threshold of the valve. This force is uni-

  that created by the magnet, that is to say the detachment force. In a particularly advantageous manner, the magnet borders the seat of the valve and the shutter member is in the form of a cone carried by a washer and the magnet is a magnetized crown provided with a conical orifice aligned with the passage of the valve, which allows to have a surface

  of significant action for magnetic attachment.

  According to another advantageous characteristic, a

  return spring acting on the shutter member,

  shovel it toward its valve seat.

  The invention also relates to the applications of such directional valves, in particular to stops of

  doors with rotational movement or translational movement.

  Thus, according to another characteristic before-

  door stop, especially for a motor vehicle, intended to connect the two parts of the joint (door / bodywork) to one another to hold them in any position, comprises: - a rigid housing, sealed, containing a fluid connected to a part of the joint, and subdivided into two chambers of variable volume, complementary, by a piston mounted in the housing by an axis integral with the

  piston (203) and at least one end of which protrudes from the box

  tier to be connected to the other part of the articulation, - the piston is provided with two directional valves with trigger threshold, opposite, connecting the two chambers when the pressure in one of the chambers exceeds that of

  the other by a difference greater than the threshold of the flap cor-

  corresponding to the direction of passage of the fluid from the chamber to

high pressure towards each other.

  According to another characteristic, the piston is

pivotally mounted in the housing.

  According to another characteristic, the piston is

sliding mounted in the housing.

  The present invention will be described below from

  in more detail using the accompanying drawings in the-

  which: - Figure 1 is a schematic sectional view of a directional valve with triggering threshold according to the prior art, - Figures 2A, 2B are graphs showing the relationship between the angular or linear displacement of the

  valve and the force exerted on the valve, Figure 2A cor-

  corresponding to the theoretical or desirable situation and the fi-

  gure 2B to the result obtained by the use of a valve according to FIG. 1, FIG. 3A is a section view similar to

  that of FIG. 1, of a directional valve with threshold of de-

  latching in the closed position according to the invention, - Figure 3B is a view of the valve of Figure 3A but in the open position, - Figure 4 shows a linear translation device with piston, equipped with two valves according to the invention,

  - Figure 5 shows a sectional view of a va-

  laughing embodiment of a linear translation device with piston according to FIG. 4, - FIG. 5A shows a detail of the shape of the front end of the piston and of the throttled passage channel, - FIG. 6 shows another mode of production of a translation device with bidirectional piston, FIG. 7 shows a door stop box fitted with valves according to the invention,

  FIG. 8A shows a first device li-

  combined neaire forming a door stop working in translation according to a first version, FIG. 8B relates to a second version of a door stop working in translation,

  - Figure 9A shows another version of an ar-

  doorstop working in translation,

  FIG. 9B is a variant of the embodiment

sation of Figure 9A.

  The present invention will be described below in more detail using an embodiment of a

  valve shown in Figures 3A, 3B.

  According to FIG. 3A, the valve of the invention is intended to connect an upstream chamber A and a downstream chamber B. These two chambers are separated by a theoretical plane PP. The valve 101 according to the invention consists of a body 102 crossed by a stepped passage of axis XX formed by an upstream passage 111 and small section and a downstream passage 112 of large section. The upstream passage 111 is situated on the side of the chamber A and the downstream passage on the side of the chamber B. These two passages form a shoulder 113 forming the valve seat 114. A shutter member 115 cooperates with this seat 114. This the shutter member is made in the form of a conical part 1151 and a washer or a disc 1152; this shutter member 115 slides in the downstream passage 112. It is pushed by a return spring 117 coming against the rear face of the washer 1152 and also bearing against a nut 118 provided with a passage 119. The nut 118

  is screwed into the downstream passage 112 provided with a thread.

  The nut 118 is drilled to act the fluid of the chamber

  A on the rear face of the shutter member 115, that is to say

say on the washer 1152.

  The shutter member 115 is made in a ma-

  subject likely to be magnetized or to cooperate with a

  mant. According to the embodiment shown, at the level of the shoulder 113, there is provided a magnet 116 in the form of a pierced washer, defining the seat 114 of the valve. This magnet 116 can also be integrated into the material of the body 102 if the latter is for example made of plastic. The seat 114 is then constituted by

the ridge of the upstream passage 111.

  In the present embodiment, the closure member has a conical shape 1151 and the seat 114 a corresponding shape. The taper may be slightly different, if necessary, to create a contact effect

  punctual improving, in some cases, sealing.

  The magnetic force attracting the obturating organ

  tion 115 against the magnet 116 and more precisely the seat 114 is directly proportional to the inverse of the square of the distance separating these two parts. This means that this force of attraction decreases very quickly as soon as the two

  parts begin to separate while at the time of con-

  tact, it is very intense. This creates an effect of

clearly pronounced threshold.

  It should be noted that the return spring 117 simply pushes the shutter member 115 towards the valve seat 114 without this spring 117 creating the shutter force of the valve and, above all, does not intervene in the de- 25 finishing of the valve opening threshold, this force

  being mainly defined by the magnetic force

tick.

  The body has a constricted passage 110, that is

  that is, a passage of relatively small diameter, which opens out

  che in the upstream passage 112 in the vicinity of the shoulder 113, in the area not covered by the magnet 116. This passage also opens outside the body 112 on the side

  from room B to communicate with this room.

  The start of the constricted passage 110 in the downstream passage 112 is such that when the valve 115 is in the closed position, the constricted passage 110 is closed. The more or less advanced position of the mouth of the passage 110 in the chamber 112 is of little importance in practice since as soon as the shutter member 115 is detached from its seat 114, the fluid pressure of the upstream chamber 114 acts on the entire section of the closure member (this section corresponds to that of the passage 112 and can easily repel the latter, by effect of pressure difference between the two faces practically of the same surface of the shutter member 115, the upstream face being subjected to the pressure of the upstream chamber A and the downstream face to that of the downstream chamber B. FIG. 3A shows the valve in the closed position and FIG. 3B the valve in open position In this last position the fluid, which is in the chamber A, at a pressure higher than that of the fluid in the chamber B, crosses the upstream passage 115 and the throttled passage 110 to arrive in chamber B. The Figure 4 shows a first application of the

  valves according to the invention. This device is for example

  terposed between two organs carrying out a translational movement between them. One of the organs is integral with a part

  of the device and, the other of the second part.

  This device consists of a housing 401 housing a piston 403 secured to a piston rod 402. The housing 401 is connected to one of the moving parts and the rod

  piston 402 to the other movement part. The piston 403 deli-

  mite in the housing 401 two chambers A, B, which contain fluid and can communicate by the passage of the fluid to

  through piston 403. This passage is controlled by two cla-

  pets 300 integrated into the piston 403. These valves act in opposite directions, that is to say that one of the valves acts when the pressure of chamber A exceeds that of chamber B by a difference in pressure greater than a threshold. In the opposite case, the other valve acts and allows communication

  between the two chambers to allow movement of the pis-

  tone 403 relative to housing 401, this displacement being blocked

  as soon as the efforts exerted on one of the parties by

  with respect to the other fall below a determined threshold.

  The detailed description of these 300 cor valves

  corresponds to that of FIGS. 3A, 3B and will not be repeated.

  It should be noted simply in this figure, that the upstream passage carries the reference 311 and the passage

strangled the reference 310.

  Figure 5 shows an alternative embodiment of the device of Figure 4, comprising a housing 501 housing

  a piston 503 secured to a piston rod 502. As before-

  cedently, the housing 501 is connected to one of the moving parts and the rod 502 to the other moving part. The piston 503 delimits in the housing 501, two chambers A, B

  which contain fluid and can communicate through the pas-

  of fluid through the piston 503. This passage is com-

  mandated by two valves 300 ', integrated in the piston 303. These

  valves also have 510 throttled passages

doubled for each valve.

  As before, the valves 300 'act

each in its direction.

  FIG. 5A shows an alternative embodiment

  of the piston 315 of the device 300 'and of the throttled passage 510'.

  This constricted passage is bent to favor the flow

  reducing the pressure losses. Passage 510 'communicates with

  passage 511 upstream of piston 315. The front face of the piston

  tone 315 has a curved part 315A, 315B adapted respectively

  form 511A, 511B of the entrance to passage 511.

  In fact, the form 315A corresponds to the form

  curve while the shape 315B corresponds to the res-

  conical aunt of the valve seat thus formed in the piston 503 or the part biting the valve seat in the piston 503 like the part 116 of FIGS. 3A, 3B. The direction of flow of the fluid through the throttled passage 510 'and

  passage 511 is represented by a curved arrow.

  Figure 6 shows an alternative embodiment

  a piston device incorporating a double valve.

  This device consists of a housing 601 comprising

  as a piston 603 also delimiting two chambers A, B. The piston 603 is integral with a rod 602. The housing 601 and

  the rod 602 are respectively connected to the two movable parts

  the. The piston 603 comprises a bidirectional valve formed by two shutter members 615A, 615B each operating in a flow direction. These two shutter members do not work simultaneously since one of the chambers A or B necessarily has a higher pressure

  to the other when the device works. Under these conditions

  tions, the shutter member located on the side of the chamber in which the greatest pressure prevails, is pushed backwards relative to its shutter position while

  the other shutter member remains in the closed position.

  This arrangement saves a lot of space.

so much.

  These two devices are bypassed by steps

wise men with constriction 610B, 610A.

  The shutter members 615A and 615B each cooperate with a valve seat 614A, 614B with a magnet 616A, 616B provided at the valve seat. In this embodiment, the two shutter members 615A, 615B are arranged head to tail separated by the compression spring 617 which tends to separate them. In the case of this double valve, the

  stepped passage 612 ends at each end with a step-

  sage of small section 611A, 611B playing the role of passage

  strangled 111, 112 of the embodiment shown in figures

res 3A, 3B.

  Finally, the shutter members 615A, 615B include

  carry a passage 616A, 616B. When the device is at rest, the shutter members 615A, 615B are separated by the spring 617 and bonded against their respective magnet. When the device is in movement, one of the two shutter members 615A, 615B comes off from its seat, according to the direction of movement, that is to say the direction of the pressure difference generated between the two chambers A, B while the other member remains fixed. The constricted passages 616A, 616B provided in each of the two shutter members 615A, 615B allow the exchange of fluid with the volume between the two throttle members 615A, 615B, allowing the relative movement of these two members. The two passages 616A, 616B opening onto the front faces of the members 11 615A, 615B, there is no overall leakage of fluid through the two passages 616A and 616B simultaneously, since the

  two members 615A, 615B are then applied against the seats

ges 614A, 614B.

  Figure 7 shows another embodiment for a pivoting stop device. This device consists of a housing 201 housing a piston 203 pivotally mounted around

  an axis 202. The piston separates the housing 201 into two chambers

  bres A, B; the piston comprises two valves according to the invention, mounted in opposite directions to operate according to the pressure difference prevailing between the two chambers A and B.

  The various means of this device not

  surrounded by the invention, are not described.

  FIGS. 8A, 8B very schematically show the application of directional valves to the production of a

door stop in translation.

  It is particularly interesting for reasons

  congestion sounds, to carry out a door stop tra-

  valiant in translation and not in rotation. For that, we

  transforms the rotational movement of axis 700 of the

  nière of the door in a translational movement through a pin 701 carried by a disc 702 secured to the axis of the door. This crankpin is connected by a connecting rod 703 to a rod of

  piston 704 carrying a piston 705 slidingly housed in a box

  tier 706 delimiting two chambers A, B. This housing 706 with

  its piston 705 and its two chambers works as the dis-

  positive of Figures 4, 5 or 6. It may include a valve

  combined or two bidirectional valves.

  FIG. 8B shows a slight variant of the embodiment of FIG. 8A. In this case, the piston rod 704 is connected not to a connecting rod but to a pusher 703A carrying a part 708 in the form of an oblong hole which receives the crank pin 701A forming a slide roller. This crank pin is also carried by a disc 702 secured to the axis 700 of

  the hinge. The rotation of the crankpin 701A causes the trans-

  lation of the oblong hole 708. This movement is transmitted by the pusher 703A to the piston rod 704 which also carries a

  piston 705 like the one in figure 8A with one or two cla-

farts 707.

  Figures 9A, 9B schematically show two other embodiments of door stops equipped with directional valves. According to FIG. 9A, the door stop comprises a

  part 800 linked to the hinge axis and part 801 so-

  bodywork. The two parts 800, 801 rotate relative to each other. Part 800 carries an axis 802 with a screw 803 and part 801 is a housing in which slides a piston 804 delimiting there two chambers A and B

  filled with fluid. The piston 804 is crossed by two cla-

  unidirectional farts 805, 806 mounted in opposition for

  put the passage of the fluid in one direction each time

  times, as already described above.

  The piston 804 carries a nut 807 receiving the screw 803. The part 800 is fixed in translation but can rotate since linked to the axis of the hinge. The housing 801 is also fixed in translation. Its piston 804 is blocked

  in rotation but free in translation inside the box

tier 801.

  By cooperation of the nut 807 and the screw 803, during a rotation of the hinge axis, the piston 804

  is pushed by screwing in the corresponding direction.

  The increase in pressure and the resulting depression on one side and the other of the piston 804 in the chambers A and B (according to the direction of movement) create a passage of liquid from one chamber to the other then retaining the piston 804 in the rotation stop position, which corresponds to the stop

Door.

  Figure 9B shows another alternative embodiment.

  door stop, including a 900 connected part

  to the axis of the hinge and a part 901 in connection with respect

  port to axis 900 and sliding in the body. The par-

  tie 901 is a housing housing a piston 904 separating the interior of the housing 901 into two chambers A and B. The piston 904 is provided with two unidirectional valves 905, 906 like those described above, working in opposite directions of passage. The piston 904 is connected by a rod 902 to the part 900. The part 900, the rod 902 and the piston 904 are fixed in translation but integral in rotation with the axis of the hinge. The screwing movement between the screw thread

  903 carried by the rod 902 and a nut 907 carried by the box

  tier 901 causes the movement of the 901 case. This movement is executed under the same conditions as above: when the door is turned and consequently its axis, this rotation

  turn part 901 and its rod 902 with its threaded part.

  As this assembly is held in translation, the screwing in

  the nut 907 produces the translation of the nut 907 and the box

  tier 901. The movement of the housing 901 with respect to the piston 904 causes an increase or a decrease in pressure in the liquid on either side of the piston 904 in the two chambers A and B. From a certain threshold, the liquid can pass through one of the one-way valves 905, 906. When the movement of the hinge stops, the assembly is blocked under the same conditions as those

described above.

Claims (10)

R E V E N D I C A T IONS   1) Directional valve with tripping threshold (1)   nant: - a stepped passage (111, 112) having as input an upstream passage (111) of small section opening into the chamber   upstream (A) and a downstream passage (112) of large diameter opening   edge in the downstream chamber (B), - these two passages of different diameters forming between them a shoulder (113) into which opens the upstream passage (111) by producing therein the valve seat (114) with which a member of obturation (115), - the throttled passage (110) connecting the interior of the valve (1), downstream of the seat (14) to the downstream chamber, characterized in that - the obturation member (115) is magnetic and - a magnet (116) is provided at the level of the valve seat (114) to attract the shutter member (115) against the valve seat.   2) Directional valve with tripping threshold according to the re-   vendication 1, characterized in that   the magnet borders the valve seat (114).   3) Directional valve with tripping threshold according to the re-   vendication 1, characterized in that the shutter member (115) is cone-shaped (1151) carried by a washer (1152) and the magnet (116) is a crown with a conical orifice aligned with the upstream passage ( 111) and forming the valve seat.   4) Directional valve with tripping threshold according to the re-   vendication 1, characterized by a return spring (117) acting on the closure member   (115) to call it back to the valve seat (114).    ) Directional valve with triggering threshold according to claim 1, characterized in that it comprises a throttled passage (510 '), bent (511A), and the surface (315A) of the piston (315) of the valve (300' ), at the location   o opens the strangled passage, is of curved shape complete that of the passage.   ) Directional valve with tripping threshold according to the re-   vendication 1, characterized in that it comprises two shutter members (615A, 615B) arranged head to tail and separated by a compression spring (617), each shutter member (615A, 615B) being magnetic to cooperate with a respective seat (614A, 614B) in the passage   stepped and each closure member being associated with a step strangled sage (610A, 610B).   7 0) Directional valve with tripping threshold according to the re-   vendication 1, characterized in that the spring (117) acting on the closure member (115) is supported on a drilled screw (118), housed in an adjustable manner in the downstream passage (112), tapped on at least a part of its length.   ) Door stop, especially for a motor vehicle,   keen to connect the two parts of the joint (door / bodywork) to each other to retain them in any position, comprising:   - a rigid housing (201), closed in leaktight manner, containing   a fluid connected to a part of the joint, and   subdivided into two chambers (A, B) of variable volume, com-   additional, by a piston (203) mounted in the housing (201) by an axis (202) integral with the piston (203) and of which at   at least one end protrudes from the housing (201) to be re-   linked to the other part of the joint, 21/05 / 1jP0812 - the piston (203) is provided with two directional valves with trigger threshold, opposite, connecting the two chambers (A, B) when the pressure in the one of the chambers exceeds that of the other by a difference greater than the threshold of the valve corresponding to the direction of passage of the fluid from the chamber at high pressure to the other, characterized by   directional valves with tripping threshold (300) are   lon any of claims 1 to 7.   9) Door stop according to claim 8, characterized in that   the piston (203) is pivotally mounted in the housing (201).   10) Door stop according to claim 8, characterized in that   the piston (403) is slidably mounted in the housing (401).   11) Door stop according to claim 8, characterized in that   it comprises a transmission device formed by a man-   tone (701) carried by the axis (700) of the hinge and transmits-   both its rotational movement to a connecting rod (703) controlling the piston rod (704, 705) with which the piston is equipped directional valves (707).   12) Door stop according to claim 8, characterized by   a transmission device formed of a crank pin (701A) in   dragged in rotation by the hinge pin (700), this crankpin   being housed in an oblong hole (708) integral with a pusher (703A) transmitting the translational movement generated by transformation of the rotational movement of the crankpin (701A)   in the oblong hole (708) in a translational movement ap-   bent to the rod (704) of the piston (707) fitted with valves   rectionnels. 13) Door stop according to claim 8, characterized by - a part (800) linked to the axis of the hinge and a part   (801) integral with the body, these two parts turn   in relation to each other, - the part (800) carrying an axis (802) with a screw (803) and the part (801) being a housing in which slides a piston (804) crossed by two valves unidirectional (805, 806) mounted in opposition, - the piston (804) carrying a nut (807) receiving the screw (803),   - The part (800) linked to the axis of the hinge being fixed in translation but free in rotation and the housing. (801) being fixed in translation, the piston blocked in rotation   being free in translation inside the housing (801).   14) Door stop according to claim 8, characterized by   - a part (900) connected to the axis of the hinge and a part   tie (901) in connection with respect to the axis (900) and in sliding   body, - the part (901) being a housing housing a piston (904) separating the interior of the housing (901) into two chambers (A and B), - the piston being provided with two unidirectional valves (905,   906) working in the opposite direction, the piston (904) being   linked by a rod (902) to the part (900), - the rod (902) carries a screw thread coming in a nut (907) carried by the housing (901), - the part (900), the rod ( 902) and the piston (904) being   fixed in translation but integral in rotation with the axis-   of the hinge to cause the screw housing (901).