GB2347732A

GB2347732A - Magnetic check valve for a door stop

Info

Publication number: GB2347732A
Application number: GB0006021A
Authority: GB
Inventors: Dominique Benoit; Pascal Guerry; Cyrille Chatel
Original assignee: MGI Coutier SA
Current assignee: Akwel SA
Priority date: 1999-03-11
Filing date: 2000-03-13
Publication date: 2000-09-13
Anticipated expiration: 2020-03-13
Also published as: FR2790812A1; FR2790812B1; GB2347732B; IT1317593B1; ES2180369A1; GB0006021D0; ITMI20000498A1; ES2180369B1; DE10011674A1

Abstract

A magnetic check valve 101 comprises two passages 111, 112 of different diameter forming valve seat 114, a valve member 115 maybe biased against seat 114 by spring 117 and held there by magnetism. A choke passage 110, which connects the valve interior to its exterior, is located adjacent seat 114. Member 115 may comprise cone 1151 carried by disc 1152 and seat 114 may comprise annular magnet 116 with a central aperture. Choke passage 110 may be curved with a complementary curve formed on member 115 (fig. 5a). Two magnetic closure members (615a, 615b, fig. 6), with respective seats (614) and choke passages (610) may be joined by a spring (617). Spring 117 may be seated against an adjustable screw 118. A doorstop for vehicles, comprising a sealed fluid chamber divided into two (A, B, fig. 4) by a piston (403) driven externally by a pin (402), has two opposing magnetic check valves (300) which allow fluid communication between chambers (A, B) when the pressure in either chamber exceeds a set threshold. The piston may be mounted to slide (fig. 4) or pivot (fig. 7). Pin (704, figs. 8a and b) may be driven by a rod (703) connected to a crank pin (701) which is connected to a hinge pin (700) or it may be driven by rotation about a screw thread located either inside (fig. 9a) or outside (fig. 9b) the doorstop.

Description

DIRECTIONAL THRESHOLD RELEASE VALVE DEVISES EOUIPPED WITH SUCH VALVES The present invention relates to a directional threshold release valve comprising : a stepped passage having at entry an upstream passage of relatively small cross-section issuing into an upstream chamber and a downstream passage of relatively larger diameter issuing into a downstream chamber, -the two passages of different diameter defining between them a shoulder into which issues the upstream passage thereby forming a valve seat which is arrange to cooperate with a closure member, -rand a choke passage connecting the interior of the valve, downstream from the valve seat, to the downstream chamber.

Directional threshold release valves are already known, designed in particular to be fitted to doorstops of motor vehicles (FR 97 12 946). The function of such valves is to open when they are subjected to a pressure difference which is greater than a predetermined threshold value and which corresponds to their direction of operation. They reclose when this pressure difference disappears. In the case of a doorstop, that means that the valve opens when the door is pushed with a force greater than the threshold value in the sense which corresponds to the opening of the valve, and the valve closes again as soon as the opening force applied to the door disappears and having created the pressure difference on the two sides of the valve.

One such valve is illustrated schematically in Fig. 1, the valve alone being shown, independently of its implementation.

The valve 1 is intended to free the passage 10 which connects the chamber A (in which it is assumed that the higher pressure exists) to the chamber B, when the difference between the two pressures exceeds the threshold for release of the valve.

The valve 1 comprises a stepped passage formed in a valve body 2 and comprises, on the side of the chamber A, a passage of small cross-section 11 and on the other side, issuing into the chamber B, a passage of larger cross-section 12. These passages define between them a shoulder 13 in which the small cross-section passage 11 defines a valve seat 14. The valve is closed by a closure member 15 in the form of a ball. This closure member is fitted in the large cross-section passage 12 in a sleeve 16 with which it is in sealing contact. This sleeve is itself fitted in the passage 12 in a sealing manner.

A spring 17 presses against the closure member 15. At its outer end, the spring 17 presses against an aperture screw 18 which is provided with an aperture 19 which extends completely therethrough. This screw 18 is screwed into a threaded part of the large cross-section passage 12 in order to compress the spring 17 in a calibrated manner, fixing the release threshold of the valve.

The sleeve 16 is clear of the choke passage 10 as it is illustrated.

The functioning of this valve 1 is as follows.

Initially, it is assumed that the fluid pressure in the two chambers A and B is the same. The piston is then in equilibrium and the valve is closed. Its closure member 15 is pressed by the spring 17 against its seat 14.

It is assumed by way of example that the pressure of the fluid in the chamber A rises and the pressure of the fluid in the chamber B falls.

The difference between the two pressures is exerted through the small cross-section passage 11 against that part of the closure member 15 which is exposed in the passage 11.

When the product of this pressure (pressure difference) and the expose surface is equal to or slightly greater than the closure force exerted by the spring 17 on the closure member 15, the closure member will lift from its seat 14.

Immediately it opens, the pressure difference is no longer exerted only against the small surface area of the closure member 15 but against the whole of that side of the closure member which is exposed to the fluid in the chamber A. In fact, the whole of the surface of the closure member 15 located on the side of the chamber A is subjected to the pressure existing in the chamber A and the whole of the surface of the closure member 15 facing towards the chamber B is subjected to the pressure of the fluid existing in that chamber B via the intermediary of the aperture 19 through the screw 18. In order to maintain the closure member 15 in the open position, it only requires a pressure difference which is much less than that necessary for the initial release of the valve, because this pressure difference is no longer exerted on the small surface of the closure member but over practically the whole cross-section of the passage 12.

The disadvantage of the known valve lies in the fact that its operation at the threshold is not sufficiently definite.

In effect, the closure member in the form of the ball which blocks the aperture through which fluid is admitted is pushed by a spring. Thus, the return force developed by the spring is proportional to the displacement of the ball. This means that the further the valve is open and the more the spring holds back the ball, this creates a very important loss of charge along a column of fluid. This does not enable one to achieve a sharp release at the moment the threshold is reached, which is explained by Figures 2A and 2B, which respectively show the ideal case and the situation in practice. A linear or angular displacement is represented along the abscissa of the two Figures and the return force of the valve is represented along the ordinate.

Fig. 2A shows that there is a sudden drop between the level F1 and the level F2 of the force F at the transition at the abscissa point aO. That is what happens there in the theoretical situation which is sought after.

Fig. 2B shows the practical situation. The transition between the level F1 and the level F3 is not made suddenly at the abscissa point ao but begins at this moment and ends at the abscissa point al, which corresponds to a less than ideal operation because the release threshold is not cleanly defined.

It is an object of the present invention to overcome these disadvantages and to provide a directional threshold release valve in which the effect at the threshold is cleanly emphasised.

To achieve this, the present invention is concerne with a directional valve of the type first mentioned above, in which: -the closure member is magnetic and a magnet is provided at the level of the valve seat to attract the closure member against the valve seat.

Since the magnetic force of attraction exerted on the closure member decreases as a function of the inverse of the square of the distance between the closure member and the magnetic element, immediately the closure member is slightly raised from its seat, the return force or the attraction of the magnetic element becomes extremely weak very rapidly.

This force is not at all augmente or substituted by a possible spring return force acting against the closure member, because the return spring is simply intended to push the closure member back, in the absence of other exterior forces, against the valve seat, without the spring being dimensioned to stick the closure member against the seat and create the restraining force corresponding to the threshold for opening the valve. This force is uniquely that created by the magnet, that is to say the unsticking force.

It is particularly advantageous if the magnet borders the valve seat and the closure member has the shape of a cone carried by a disc and the magnet is annular around a conical aperture aligned with the valve passage, which gives one an action surface which is important for the magnetic engagement.

In accordance with another preferred advantageous feature, there is provided a return spring acting against the closure member returning the latter towards its valve seat.

The invention is equally concerne with the use of such directional valves, in particular their application to doorstops arrange for rotational movement or for translational movement.

Thus, there is also provided in accordance with the invention a doorstop, in particular for motor vehicles, arrange to connect two articulated components (door/bodywork) in order to hold them in any given position, comprising : a rigid, sealed closed housing containing a fluid and connecte to one articulated component, the housing being divided into two complementary chambers of variable volume by a piston mounted in the housing on a pin which is fixedly secured to the piston and at least one extremity of which extends outside the housing for connection to the other articulated component, -in which the piston is provided with two directional threshold release valves, arrange in opposition, and providing communication between the two chambers when the pressure in one of the chambers exceeds that of the other by an amount which is greater than the threshold of the valve, corresponding to the direction of flow of the fluid from the higher pressure chamber towards the other.

According to one embodiment, the piston is mounted pivotally in the housing.

According to another embodiment, the piston is mounted slidably in the housing.

The present invention will now be described hereinafter in more detail, with reference to the accompanying drawings, in which : Fig. 1 is a schematic sectional view through a directional threshold release valve according to the prior art; Figs. 2A and 2B are graphical representations showing the relationship between the angular or linear displacement of the valve and the force exerted on the valve, Fig. 2A corresponding to the theoretical or desirable situation and Fig. 2B showing the result obtained by using a valve according to Fig. 1 ; Fig. 3A is a sectional view, similar to that of Fig. 1, through a directional threshold release valve according to the invention, in the closed position ; Fig. 3B is a view of the valve of Fig. 3A but in the open position; Fig. 4 shows a device for the linear piston translation, equipped with two valves according to the invention ; Fig. 5 is a sectional view through a variation of the embodiment of a linear translation piston device according to Fig. 4 ; Fig. 5A shows a detail of the shape of the front extremity of the piston and of the choke passage ; Fig. 6 shows another embodiment of a bidirectional translation piston device ; Fig. 7 shows a housing of a doorstop equipped with valves according to the invention ; Fig. 8A shows a first linear combination device forming a doorstop working in translation according to a first embodiment; Fig. 8B shows a second embodiment of a doorstop working in translation ; Fig. 9A shows another embodiment of a doorstop working in translation ; and Fig. 9B shows a variation of the embodiment of Fig. 9A.

The present invention will be described hereinafter in more detail with reference to an embodiment of a valve as shown in Figs. 3A and 3B.

According to Fig. 3A, the valve in accordance with the invention is intended to bring into communication an upstream chamber A and a downstream chamber B. These two chambers are separated by a theoretical plane PP.

The valve 101 in accordance with the invention comprises a body 102 which is traverse by a stepped passage on axis XX formed by an upstream passage 111 of relatively small crosssection and a downstream passage 112 of relatively large cross-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 define a shoulder 113 which forms a valve seat 114. A closure member 115 cooperates with the valve seat 114. This closure member has a conical portion 1151 and a ring or disc 1152. This closure member 115 slides in the downstream passage 112. It is pushed by a return spring 117 seated at one end against the rear face of the ring 1152 and seated at the other end against a nut 118 provided with an aperture 119 therethrough. The nut 118 is screwed into the downstream passage 112 which is provided with a thread. The nut 118 is aperture in order to enable the fluid in the chamber B to act on the rear face of the closure member 115, that is to say on the disc 1152.

The closure member 115 is made of a material which is capable of being magnetised or which will cooperate with a magnet.

According to the illustrated embodiment, at the level of the shoulder 113, there is provided a magnet 116 in the form of an aperture disc, defining the valve seat 114.

This magnet 116 can equally well be integrated into the material of the body 102 if the latter is made for example of a plastics material. The seat 114 would then be constituted by the margin of the upstream passage 111.

In the present embodiment, the closure member presents a conical portion 1151 and the seat 114 has a corresponding shape. The conicity can be slightly different, if the need arises, in order to create a contact effect at a single point, improving the sealing tightness in certain cases.

The magnetic force drawing the closure member 115 against the magnet 116, and more precisely against 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 diminishes very rapidly immediately the two parts begin to separate from one another, while at the moment of contact the force is very intense. This enables one to create a cleanly defined threshold action.

It should be observe that the return spring 117 simply pushes the closure member 115 towards the valve seat 114 without the spring 117 either creating the closure force of the valve or, above all, intervening in the definition of the opening threshold of the valve, this opening force being defined principally by the magnetic force.

The valve body comprises a choke passage 110, that is to say a passage of relatively small diameter which issues into the downstream passage 112 adjacent to the shoulder 113, in the zone which is not covered by the magnet 116. This passage 110 issues at the other end at the exterior of the valve body at the side of chamber B in order to communicate with this chamber.

The mouth of the choke passage 110 in the downstream passage 112 is such that when the valve 115 is in the closed position the choke passage 110 is closed. Whether the position of the mouth of the passage 110 in the chamber 112 is further forward or less far forward is of little practical importance, since immediately the closure member 115 has lifted off its seat 114, the pressure of the fluid in the upstream chamber 111 acts against the whole of the crosssection of the closure member (this cross-section corresponding to that of the passage 112) and can easily push the closure member back, by the effect of the difference in pressure between the two faces of the closure member 115 which have practically the same surface area, 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 shows the valve in the open position. In this latter position the fluid which is in the chamber A, at a pressure which is higher than that of the fluid in the chamber B, flows through the upstream passage 111 and through the choke passage 110 in order to reach the chamber B.

Fig. 4 shows a first application of the valves according to the invention. This device is positioned for example between two members which between them carry out a translatory movement. One of the members is fixedly attache to one part of the device and the other to the other part of the device.

This device comprises a housing 401 carrying a piston 403 which is fixed securely to a piston rod 402. The housing 401 is connecte to one of the moving parts and the piston rod 402 is connecte to the other moving part. The piston 403 defines within the housing 401 two chambers A and B which contain fluid and can communicate by the passage of fluid through the piston 403. This passage of fluid is controlled by two valves 300 which are integrated into the piston 403. These valves act in opposing senses, that is to say that one of the valves acts when the pressure in the chamber A exceeds that of the chamber B by a pressure difference which is greater than a threshold value. In the reverse case, the other valve acts and permits communication between the two chambers to permit displacement of the piston 403 in relation to the housing 401, this displacement being blocked immediately the force exerted on the one part in relation to the other falls below a predetermined threshold value.

The detailed description of these valves 300 corresponds to that of Figures 3A and 3B and therefore does not need to be repeated.

It should be noted simply that in this Figure the upstream passage is indicated by the reference numeral 311 and the choke passage by the reference numeral 310.

Fig. 5 shows a variation of the device of Fig. 4, comprising a housing 501 carrying a piston 503 which is fixed securely to a piston rod 502. As before, the housing 501 is connecte to one of the moving parts and the rod 502 to the other moving part. The piston 503 defines within the housing 501 two chambers A and B which contain fluid and can communicate by the passage of fluid through the piston 503.

This passage of fluid is controlled by two valves 300t which are integrated into the piston 503. These valves again comprise choke passages 510, provided here as a pair for each valve.

As before, the valves 300'tact each in their own direction.

Fig. 5A shows a modifie piston 315 of valve 300'rand a modifie choke passage 510'. This choke passage is curved in order to favour the flow, reducing the loss of charge. The choke passage 510'communicates with the passage 511 upstream from the piston 315. The forward face of the piston 315 inclues a curved portion 315A, 315B, matched respectively to the contours 511A and 511B of the entry to the passage 511.

In fact, the contour 315A corresponds to the curved shape, whereas the contour 315B corresponds to the remaining conical part of the valve seat thus formed in the piston 503 or the part bordering the valve seat in the piston 503, like the element 116 of Figures 3A and 3B. The direction of the flow of fluid through the choke passage 510'rand through the passage 511 is indicated by a curved arrow.

Fig. 6 shows another embodiment of a piston device incorporating a double valve.

This device comprises a housing 601 carrying a piston 603 which likewise defines two chambers A and B. The piston 603 is fixed securely to a rod 602. The housing 601 and the rod 602 are connecte respectively to the two moving members.

The piston 603 comprises a bidirectional valve formed by two closure members 615A, 615B functioning each in one direction of flow. These two closure members do not work simultaneously, since one of the chambers A or B necessarily has a higher pressure than the other when the device functions. Under these conditions, the closure member which is located on the side of the chamber in which the greater pressure is present is pushed backwards in relation to its closure position, while the other closure member remains in a position of closure.

This disposition of the parts gives an important gain in terms of space.

These two closure members are skirted by the choke passages 610B, 610A.

The closure members 615A and 615B cooperate each with a valve seat 614A, 614B with a magnet 616A, 616B provided at the level of the valve seat. In this embodiment, the two closure members 615A, 615B are arrange head to tail, separated by a compression spring 617 which biases them apart.

In the case of this double valve, the stepped passage 612 is terminated at each end by a passage 611A, 611B of relatively small cross-section, playing the role of the passages 111, 112 in the embodiment shown in Figs. 3A and 3B.

Finally, the closure members 615A, 615B each include a passage 616A, 616B. When the device is at rest, the closure members 615A, 615B are biased apart by the spring 617 and stick against their respective magnes. When the device is in motion, one of the two closure members 615A, 615B lifts from its seat, according to the direction of movement, that is to say the direction of the difference in pressure engendered between the two chambers A, B, while the other closure member remains fixed in position. The choke passages 616A, 616B provided in each of the two closure members 615A, 615B permit the exchange of fluid with the zone between the two closure members 615A, 615B, permitting the relative movement of these two members. The two choke passages 616A, 616B issue at the front faces of the closure members 615A, 615B. There is no general escape of fluid through the two passages 616A and 616B simultaneously, since the two closure members 615A, 615B are then biased against their seats 614A, 614B.

Fig. 7 shows another mode of utilisation, for a pivot able stop device. This device comprises a housing 201 carrying a piston 203 which is mounted pivotally about an axis 202. The piston divides the housing 201 into two chambers A, B ; the piston comprises two valves according to the invention, mounted in opposite senses to function according to the pressure difference which exists between the two chambers A and B.

The other parts of this device are not relevant to the present invention and will therefore not be described.

Figs. A and B show, very schematically, the use of directional valves for the creation of a doorstop with translator movement.

It is particularly attractive, for reasons of avoiding bulkiness, to be able to provide a doorstop which works in translation and not in rotation. For this, one transforms the mouvement of rotation of a pin 700 of a door hinge into a translatory movement, thanks to a crank pin 701 carried by a disc 702 which is fixedly connecte to the hinge pin of the door. This crank pin is connecte by a connecting rod 703 to a piston rod 704 carrying a piston 705 which is mounted for sliding movement in a housing 706 which defines two chambers A and B. This housing 706 with its piston 705 and its two chambers functions just like the devices of Figs. 4, 5 or 6.

It may comprise a combination valve or two bidirectional valves.

Fig. 8B shows a slight variation of the embodiment of Fig. 8A. In this case, the piston rod 704 is connecte not to a connecting rod but to a push rod 703A carrying a part 708 having an elongate hole which receives the crank pin 701A so as to form a sliding wheel. The crank pin is also carried by a disc 702 which is fixed securely to the hinge pin 700.

The rotation of the crank pin 701A causes translatory movement of the elongate hole 708. This movement is transmitted by the push rod 703A to the piston rod 704 whch again carries a piston 705, just like that of Fig. a, with one or two valves 707.

Figs. 9A and 9B show schematically two other embodiments of doorstop equipped with directional valves.

According to Fig. 9A, the doorstop comprises an element 800 connecte to the hinge pin and an element 801 which is fixed securely to the bodywork. The two elements 800, 801 turn one in relation to the other. The element 800 carries a pin 802 with a screw 803, and the element 801 is a housing in which slides a piston 804 which defines two chambers A and B filled with fluid. The piston 804 is traverse by two unidirectional valves 805, 806 mounted in opposition to permit the passage of fluid in a single direction each time, as has already been described above.

The piston 804 has a nut 807 which receives the screw 803.

The element 800 is fixed for translator movement but can turn since it is connecte to the hinge pin. The housing 801 is likewise fixed for translator movement. Its piston 804 is blocked against rotational movement but is free for translator movement within the interior of the housing 801.

By cooperation between the nut 807 and the screw 803, at the time of a rotation of the hinge pin, the piston 804 is pushed in the corresponding direction by the screwing movement. The increase and the decrease of the pressure which results from this on the one side and on the other side of the piston 804 in the chambers A and B (in accordance with the direction of movement) create a passage of liquid from one chamber towards the other and then the stoppage of the piston 804 in the position of stopped rotation which corresponds to the arrest of the door.

Fig. B shows another variation of a doorstop, comprising an element 900 connecte to the hinge pin and an element 901 linked in relation to the element 900 and slidable in the bodywork. The element 901 is a housing carrying a piston 904 which divides the interior of the housing 901 into two chambers A and B. The piston 904 is provided with two unidirectional valves 905, 906, as described above, working in opposing directions.

The piston 904 is connecte by a rod 902 to the element 900. The element 900, the rod 902 and the piston 904 are fixed for translator movement but are fixedly secured, for rotation, to the hinge pin. The screwing movement between the thread of the screw 903 carried by the rod 902 and a nut 907 carried by the housing 901 generates the movement of the housing 901. This movement is performed in the same conditions as described above ; when one turns the door and as a consequence turns its hinge pin, this rotation causes the element 901 to turn and thus its rod 902 with its threaded part. As this assembly is held for translator movement, the screwing action in the nut 907 produces the translator movement of the nut 907 and of the housing 901. The movement of the housing 901 in relation to the piston 904 causes an increase or decrease of the pressure in the liquid on the two sides of the piston 904 in the two chambers A and B. On reaching a certain threshold, the liquid can pass through one of the unidirectional valves 905, 906. When the movement of the hinge stops, the assembly is blocked in the same manner as already described above.

Claims

CLAIMS:

1. Directional threshold release valve comprising : a stepped passage having at entry an upstream passage of relatively small cross-section issuing into an upstream chamber and a downstream passage of relatively larger diameter issuing into a downstream chamber, -raid two passages of different diameter defining between them a shoulder into which issues the upstream passage thereby forming a valve seat which is arrange to cooperate with a closure member, -a choke passage connecting the interior of the valve, downstream from the valve seat, to the downstream chamber, -the closure member being magnetic, -a magnet at the level of the valve seat to attract the closure member into engagement with the valve seat, -the choke passage issuing into the downstream passage adjacent to said shoulder in a zone not covered by the magnet, and -a return spring acting on the closure member to bias it towards the valve seat.

2. Directional threshold release valve according to claim 1, in which the magnet borders the valve seat.

3. Directional threshold release valve according to claim 1 or 2, in which the closure member is in the form of a cone carried by a disc and the magnet is annular around a conical aperture aligned with the upstream passage and forming the valve seat.

4. Directional threshold release valve according to claim 1, 2 or 3, which comprises a choke passage having curvature, and the surface of the piston of the valve, at the place where the choke passage issues, has a curved shape complementary to that of the passage.

5. Directional threshold release valve according to any preceding claim, which comprises two closure members arrange head to tail and separated by a compression spring, each closure member being magnetic and arrange to cooperate with a respective seat in the stepped passage, and each closure member being associated with a respective choke passage.

6. Directional threshold release valve according to any preceding claim, in which the spring acting against the closure member is seated against an aperture screw which is mounted adjustably in the downstream passage, with said downstream passage being threaded over at least a part of its length.

7. Doorstop, particularly for motor vehicles, arrange to connect two articulated components (door/bodywork) in order to hold them in any given position, comprising : a rigid, sealed closed housing containing a fluid and connecte to one articulated component, the housing being divided into two complementary chambers of variable volume by a piston mounted in the housing on a pin which is fixedly secured to the piston and at least one extremity of which extends outside the housing for connection to the other articulated component, -in which the piston is provided with two directional threshold release valves, arrange in opposition, and providing communication between the two chambers when the pressure in one of the chambers exceeds that of the other by an amount which is greater than the threshold of the valve, corresponding to the direction of flow of the fluid from the higher pressure chamber towards the other, -in which the directional threshold release valves are valves in accordance with any one of claims 1 to 6.

8. Doorstop according to claim 7, in which the piston is mounted pivotally in the housing.

9. Doorstop according to claim 7, in which the piston is mounted for sliding movement in the housing.

10. Doorstop according to claim 7, comprising a transmission device having a crank pin carried by a hinge pin and arrange to transmit its rotational movement to a connecting rod controlling a piston rod, the piston of which is fitted with directional valves.

11. Doorstop according to claim 7, comprising a transmission device having a crank pin arrange to be driven rotationally by a hinge pin, said crank pin being mounted in an elongate aperture which is fixedly connecte to a push rod arrange to transmit the translator movement engendered by transformation of the rotation of the crank pin in the elongate aperture into a translator movement to a piston rod whose piston is provided with directional valves.

12. Doorstop according to claim 7, in which : -one component is connecte to a hinge pin and the other component is fixedly connecte to the bodywork, said two components being arrange to turn one in relation to the other, -raid one component carries a shaft having a screw and said other component comprises a housing in which slides a piston which is traverse by two unidirectional valves mounted in opposition, -raid piston is provided with a nut receiving the screw, -rand said one component connecte to the hinge pin is fixed for translator movement but is free to rotate and the housing is fixed for translator movement, the piston blocked against rotation being free for translator movement within the housing.

13. A doorstop according to claim 5, substantially as hereinbefore described with reference to the accompanying drawings.

13. Doorstop according to claim 7, in which : -one component is connecte to a hinge pin and the other component is linked in relation to the hinge pin and is slidable in the bodywork, -raid other component comprises a housing carrying a piston dividing the interior of the housing into two chambers, -the piston is provided with two unidirectional valves working in opposite senses, with the piston being connecte by a piston rod to said one component, -the piston rod has a screw thread arrange to engage with a nut carried by the housing, -rand said one component, the piston rod and the piston are fixed for translator movement but are fixedly secured, for rotation, to the hinge pin in order to generate the movement of the housing by the screwing effect.

14. A directional threshold release valve substantially as hereinbefore described with reference to the accompanying drawings.

15. A doorstop substantially as hereinbefore described with reference to the accompanying drawings.

Amendments to the claims have been filed as follows

1. Directional threshold release valve comprising : a stepped passage having at entry an upstream passage of relatively small cross-section issuing in use into an upstream chamber and a downstream passage of relatively larger diameter issuing in use into a downstream chambrer, -raid two passages of different diameter defining between them a shoulder into which issues the upstream passage thereby forming a valve seat which is arrange to cooperate with a closure member, a choke passage connecting the interior of the valve, downstream from the valve seat, to the downstream chamber, -the closure member being magnetic and in the form of a cone carried by a disc, a magnet at the level of the valve seat to attract the closure member into engagement with the valve seat, the magnet being annular around a conical aperture aligned with the upstream passage and forming the valve seat, -the choke passage issuing into the downstream passage adjacent to said shoulder in a zone not covered by the magnet, and a return spring acting on the closure member to bias it towards the valve seat.

2. Directional threshold release valve according to claim 1, in which the choke passage has curvature, and the surface of the piston of the valve, at the place where the choke passage issues, has a curved shape complementary to that of the passage.

3. Directional threshold release valve according to claim 1 or 2, which comprises two closure members arrange back to back and separated by a compression spring, each closure member being magnetic and arrange to cooperate with a respective seat in the stepped passage, and each closure member being associated with a respective choke passage.

4. Directional threshold release valve according to claim 1, in which the spring acting against the closure member is seated against an aperture screw which is mounted adjustably in the downstream passage, with said downstream passage being threaded over at least a part of its length.

5. Doorstop, particularly for motor vehicles, arrange to connect two articulated components (door/bodywork) in order to hold them in any given position, comprising : a rigid, sealed closed housing containing a fluid and connecte to one articulated component, the housing being divided into two complementary chambers of variable volume by a piston mounted in the housing on a pin which is fixedly secured to the piston and at least one extremity of which extends outside the housing for connection to the other articulated component, -in which the piston is provided with two directional threshold release valves, arrange in opposition, and providing communication between the two chambers when the pressure in one of the chambers exceeds that of the other by an amount which is greater than the threshold of the valve, corresponding to the direction of flow of the fluid from the higher pressure chamber towards the other, -in which the directional threshold release valves are valves in accordance with any one of claims 1 to 4.

6. Doorstop according to claim 5, in which the piston is mounted pivotally in the housing.

7. Doorstop according to claim 5, in which the piston is mounted for sliding movement in the housing.

8. Doorstop according to claim 5, comprising a transmission device having a crank pin carried by a hinge pin and arrange to transmit its rotational movement to a connecting rod controlling a piston rod carrying said piston, said piston being fitted with the directional valves.

9. Doorstop according to claim 5, comprising a transmission device having a crank pin arrange to be driven rotationally by a hinge pin, said crank pin being mounted in an elongate aperture which is fixedly connecte to a push rod arrange to transmit the translatory movement engendered by transformation of the rotation of the crank pin in the elongate aperture into a translatory movement to a piston rod carrying said piston.

10. Doorstop according to claim 5, in which : -one component is connecte to a hinge pin and the other component is fixedly connecte to the bodywork, said two components being arrange to turn one in relation to the other, -raid one component carries a shaft having a screw and said other component comprises the housing in which slides the piston which is traverse by two unidirectional valves mounted in opposition, -raid piston is provided with a nut receiving the screw, -rand said one component connecte to the hinge pin is fixed for translatory movement but is free to rotate and the housing is fixed for translatory movement, the piston blocked against rotation being free for translatory movement within the housing.

11. Doorstop according to claim 5, in which : -one component is connecte to a hinge pin and the other component is linked in relation to the hinge pin and is slidable in the bodywork, -raid other component comprises the housing carrying the piston dividing the interior of the housinginto two chambers, -the piston is provided with two unidirectional valves working in opposite senses, with the piston being connecte by a piston rod to said one component, -the piston rod has a screw thread arrange to engage with a nut carried by the housing, -rand said one component, the piston rod and the piston are fixed for translatory movement but are fixedly secured, for rotation, to the hinge pin in order to generate the movement of the housing by the screwing effect.

12. A directional threshold release valve according to claim 1, substantially as hereinbefore described with reference to the accompanying drawings.