Device for cutting a belt

A cutting mechanism (30) for a safety belt (10), the cutting mechanism (30) including a case (32), a passage (34) running through the case and making it possible to mount the cutting mechanism (30) on the belt (10) to be cut, and cutting elements (42) for the seatbelt (10), situated inside the case, the cutting elements (42) include a wire (44) and elements for heating (46) the wire. A process for cutting a safety belt (10), includes using a wire (44) and elements for heating (46) the wire in order to cut the belt with the heated wire.

The present invention relates to a mechanism enabling a seatbelt to be cut in a vehicle to allow the belted passenger to free himself and leave the vehicle in an emergency.

Private vehicles as well as certain public transport vehicles are equipped with seatbelts designed to prevent passengers' bodies from being projected through the vehicle's windows, against the dashboard or against the seats, during an accident such as running off the road or collision with another vehicle.

In theory, after an accident and insofar as he is still conscious and is not seriously injured, each passenger can free himself from his seatbelt on his own by releasing the buckle of said seatbelt from its attachment, the attachment including a push button enabling the buckle to be released when it is pushed in.

However, several facts are liable to hinder the passenger from freeing himself from his seatbelt easily and quickly.

For example, most seatbelts are now equipped with grippers allowing the seatbelt attachment to be pulled backward during a collision, namely in order to tighten the belt and press the passenger's body against his seat.

Such grippers, located between the attachment of the belt and the point where said attachment is attached to the vehicle chassis, exert a tractive force on the belt, even after their actuation.

And that residual tractive force creates a force opposing the inward pushing movement of the push button, thus preventing the passenger from freeing himself easily, especially if he is weakened by the force of the collision.

At the same time, the other safety elements of the vehicle, such as the airbags, or certain sections or equipment of the vehicle deformed or moved due to the collision may hinder the passenger's movements and access to the push button of the attachment.

Lastly, following an accident, some passengers, panicked or weakened by the collision, may take quite a while to free themselves from their seatbelt on their own using the standard push button.

Various mechanisms have thus been envisaged to enable the passengers to free themselves easily and quickly after a collision or accident.

Document EP-0561355 provides for a simple cutting system, placed on the seatbelt and actuated by the passenger.

In greater detail, said cutting mechanism includes two sections clipped onto the seatbelt and inside of which a blade slides, and the movement of the blade causing the cutting of the seatbelt occurring when the passenger pulls on the mechanism using a grip ring provided at the end of the mechanism opposite the one equipped with the blade.

Although very simple to use, this cutting mechanism nevertheless requires decision-making and action by the passenger.

In addition, a seatbelt being designed to withstand tractive efforts of several tonnes, manually cutting the belt may demand too much effort for some passengers, weakened or having become incapable as a result of the accident.

Document WO-2013/043066 describes a cutting mechanism not requiring effort by the passenger.

According to that document, the cutting mechanism takes the form of a cylindrical body with an internal housing in which a sliding blade is mounted, and the cylindrical body also includes two slits to run the seatbelt through.

Advantageously, the blade is moved to cut the seatbelt using an explosive charge or a generating of gas triggered remotely by an electrical signal from the vehicle's electronics, preferably when the vehicle is finally immobile after a collision and at the end of a certain period after the impact.

A disadvantage of the cutting mechanism in that document WO-2013/043066 lies in the use of an explosive charge or a gas generator to move the blade.

On the one hand, such drive means can prove to be dangerous for the passengers of the damaged vehicle.

On the other hand, the chemical functioning of such drive means can change over time, which harms the quality and reliability of the cutting.

Lastly, the use of such means requires an enhanced and thus costly design of the body of the mechanism because the blade must be stopped in motion whereas the increase in pressure propels it at high speed and with a high degree of acceleration.

The present invention aims to mitigate the disadvantages of the prior art.

For this purpose, the present invention relates to a seatbelt cutting mechanism; the cutting mechanism includes a casing, a passage running through said casing and making it possible to mount the cutting mechanism on the seatbelt to be cut, and means of cutting the seatbelt, located inside the casing.

According to the invention, the cutting mechanism is characterised in that the cutting means include a wire and means for heating said wire.

Thanks to this design, the cutting means of the cutting mechanism according to the invention are less dangerous for the belted passenger than cutting means driven by explosive charge or gas release.

In addition, the use of a hot wire improves the quality of the cutting effected by the cutting means.

From the perspective of their operation, the wire being preferably heated by an autonomous electrical supply, such cutting means offer better reliability than chemically operated means.

Lastly, this design with a hot wire does not require a mechanically reinforced casing and turns out to be less costly.

At the same time, the invention also covers a seatbelt equipped with this cutting mechanism, as well as a process for cutting a seatbelt consisting of using a wire and means of heating said wire in order to cut said seatbelt with the heated wire.

As illustrated inFIG. 1, the present invention relates to the cutting of a seatbelt10provided in the passenger compartment12of a vehicle in order to prevent a passenger from being projected out of his seat14during an impact, said impact being due to an accident or running off the road.

In well-known manner, and depending on whether a two-point or three-point seatbelt is involved, the seatbelt10includes at least one end161,162connected securely to the chassis18of the vehicle through a fastening mechanism20, and at least one buckle22connected securely to the chassis18of the vehicle by an attachment24.

Said attachment24is also connected securely to the chassis18of the vehicle by a fastening mechanism26.

And said attachment24includes means to hold the buckle22with a push button making it possible to release the buckle22.

In the example shown inFIG. 1, the seatbelt10is three-point because it comprises two ends upper161and lower162connected securely to the chassis18of the vehicle, and the buckle22is mounted sliding between those two ends161,162in order to be able to adapt the length of the seatbelt10to the passenger's body size.

Advantageously, a coiler26and a loop28, both connected securely to the chassis18of the vehicle, can be provided between the buckle22and the high end161of the seatbelt10so that the length of the seatbelt10adapts automatically to the passenger's body size.

In order to free the passenger from his seatbelt automatically after an impact, the present invention provides for a cutting mechanism30of said seatbelt10.

AsFIG. 2illustrates in greater detail, said cutting mechanism30includes a casing32, and a passage34running through said casing32.

As can be seen inFIG. 1, the passage34running through makes it possible to mount the cutting mechanism30on the seatbelt10to be cut: the seatbelt10passing through the passage running through the casing32.

Advantageously, the passage running through34makes it possible to mount the casing32in a sliding manner on the seatbelt10. Thus, the cutting mechanism30can be moved by the passenger to a position on the seatbelt10in which it does not disturb his comfort.

Preferably, the cutting mechanism30is positioned between the buckle22of the seatbelt and one end161,162of the seatbelt10connected securely to the chassis18of the vehicle.

Thus, the cutting mechanism30may be positioned in the vicinity of the buckle22of the seatbelt10and so as to rest on the seat14and not on the passenger.

Advantageously, and in particular in the event that an end161,162of the seatbelt10is connected to the chassis18of the vehicle by a coiler26, the cutting mechanism30includes upper36and lower joints38protecting the entrance40of the passage running through34.

Such joints36,38, shown inFIG. 2reduce the impact of the casing32against the coiler26or the loop28at the time of each coiling of the seatbelt10in the coiler26, i.e., each time the passenger leaves the vehicle.

According to the invention, and as illustrated byFIGS. 3, 4 and 5, the cutting mechanism30includes means of cutting42the seatbelt10that are located in the interior I of the casing32.

According to an important characteristic of the invention, the cutting means42include a wire44and a means of heating46of said wire.

In a general manner, the present invention covers a process for cutting a seatbelt10in which wire44is used when it is hot in order to cut the belt10in the interior I of the casing32.

According to this cutting process, the wire44and the means of heating46of said wire are used to cut the belt10with the heated wire44.

As illustrated inFIG. 4, the wire44takes a passive state in which the wire44is away from the seatbelt10.

And, as illustrated inFIGS. 3 and 5, the wire44also takes an active state in which the wire44is heated by the means of heating46and touching the belt10in order to cut it.

Thus, the wire44is by default in its passive state, and it goes into its active state only when the belt10must be cut after a collision, and preferably after having allowed a certain time to elapse after the vehicle has stopped moving.

In a preferred method of implementing the cutting means42, the active state of the wire44corresponds to an active position taken by the wire44, illustrated inFIGS. 3 and 5, different from a passive position, illustrated inFIG. 4, taken by the wire44and corresponding to the passive state of said wire44.

Thus, and still in a preferred method of implementation of the cutting means42, the wire44is maintained in its passive position by at least one low melt element48, and the wire44goes from its passive position to its active position when said wire44is heated and the low melt element or elements48at least partially melt under the effect of the heat of the wire44.

In greater detail, since the wire44moves toward the belt10when it goes from its passive position to its active position, at least one low melt element48comes to rest against the wire44so as to keep said wire44away from the seatbelt10when said low melt element or elements48are not melted and when said low melt element or elements48releasing the wire44in such a way that the wire44moves toward the belt10when said low melt element or elements48at least partially melt.

In a preferred method of construction of said low melt means of support on the wire44, two low melt elements481,482situated on each side of the traversing passage34create, respectively, two points of support P1, P2on the wire44making it possible to remove the wire44from the seatbelt10when said two low melt elements481,482are not melted.

In the present invention, the moving of the means of cutting the seatbelt10, namely the wire44, from their passive position to their active position is thus simply obtained by the ability of the low melt elements48,481,482to melt under the effect of the heat of the wire44.

Advantageously, said low melt elements to move the wire44provide operation that is reliable over time, not dangerous and not needing a mechanically strengthened design of the casing32of the cutting mechanism30.

In addition to the low melt elements48,481,482, and in order to position the wire44when it is heated in the best active position for cutting the seatbelt10, the cutting means42include two stops501,502situated on each side of the traversing passage34.

Those two stops501,502are respectively appended to the low melt elements481,482, and they create, respectively, two points of support P3, P4on the wire44.

Since the traversing passage34extends parallel to a longitudinal median plane PML of the casing32and at a height H341that is equal on each side to said longitudinal median plane PML, the two points of support P3, P4created by the two stops501,502make it possible to stop the movement of the wire44so as to largely maintain said wire44in the longitudinal median plane PML of the traversing passage34.

Preferably, the cutting mechanism30includes in interior I of the casing32at least one element, such as a transversal joint52visible inFIGS. 3 and 4, allowing the belt10to be maintained parallel to the longitudinal median plane PML of the casing32and in such a way that the thickness E10of the seatbelt extends equally on each side of said longitudinal median plane PML.

Thus, when the low melt elements481,482melt and release the wire44, the wire44is largely stopped in the longitudinal median plane PML of the casing32and thus in the middle of the thickness E10of the seatbelt10, which improves the quality and reliability of the cut.

To be put in motion from its passive position to its active position, the wire44could be produced in an elastic, deformable material: the wire44being arranged relative to the stops501,502in such a way that its release by the melting, even partial, of the low melt elements481,482allows it to return to its initial shape and to its active position.

However, in a preferred method of implementation of the cutting means42, the wire44is moved to the active state, and thus to its active position, by at least one wire-strainer54pulling on one of the ends56,58of the wire.

More precisely, the wire-strainer54leads said end56,58of the wire at least to the level of the longitudinal median plane PML of the casing32.

To guarantee the quality and reliability of the cut of the seatbelt10, it is preferable for the wire-strainer54to lead the end56,58of the wire above the longitudinal median plane PML of the casing32. Thus, the central portion64of the wire44running through the traversing passage34completely runs through the thickness E10of the seatbelt10.

To better improve the quality and reliability of the cutting of the seatbelt10, the cutting means42include two wire-strainers541,542situated on each side of the traversing passage34and pulling respectively on the two ends56,58of the wire44.

In making it possible to tackle the cutting of the seatbelt10on its two lateral sides F1, F2, said pair of wire-strainers541,542reduces the risk of the two pieces M1, M2of the seatbelt10cut by the wire44remaining connected along one of the sides F1, F2of the seatbelt10.

Advantageously, the two wire-strainers541,542maintain, respectively, the two ends56,58of the wire44above the longitudinal median plane PML of the casing32when the wire44is in the active state, as well as in the passive state. It is thus ensured that the wire44indeed comes to rest on the low melt elements481,482when it is in the passive position and that said wire indeed comes to rest on the stops501,502when it is in the active position.

In a particular method of construction, the wire-strainers541,542are mounted rotatable relative to a central body62of the cutting means42and around axes A1, A2parallel to the longitudinal median plane PML.

In addition, the wire-strainers541,542are constantly pushed back to the outside E of the casing32by retaining means60mounted between said central body62and said wire-strainers541,542.

Thus, when the low melt elements481,482release the wire44, the upper ends721,722of said wire-strainers541,542are driven to the outside E of the casing32, and, consequently, the central portion64of the wire44is driven to the level of the longitudinal median plane PML and the wire44is indeed resting on the stops501,502.

The retaining means60are preferably in the form of two pins661,662mounted sliding in two blind holes681,682provided in the central body62of the cutting means42, and two springs701,702placed in the bottom of the blind holes681,682, behind the pins661,662.

It is also preferable, since the means of heating46the wire44are electrical, for the wire-strainers541,542to be electrically isolated from the pins661,662by inserts741,742provided in the wire-strainers541,542at their point of contact with said pins661,662.

In the design of the cutting means42according to the invention:the low melt elements481,482form points of support P1, P2on the wire44situated below the longitudinal median plane PML of the casing32as long as said low melt elements481,482are not subjected to the heat of the wire44,the stops501,502form points of support P3, P4on the wire44situated in the longitudinal median plane PML of the casing32when the low melt elements481,482are subjected to the heat of the wire44, andthe tops761,762of the upper ends721,722of the wire-strainers541,542are situated above the longitudinal median plane PML of the casing32and above the points of support P1, P2and P3, P4formed by the low melt elements481,482and the stops501,502when the wire44is in its active state as well as when the wire44is in its passive state.

To reduce the encumbrance of the cutting means42, the wire-strainers541,542are mounted outside of the low melt elements481,482and the stops501,502.

And, in order to prevent contact between the melting materials of the low melt elements481,482when the wire44is heated, said low melt elements481,482are mounted outside of the stops501,502.

In a preferred method of construction of the cutting means42, with the height H34of the traversing passage34running perpendicular to the longitudinal median plane PML, and its width L34running parallel to the longitudinal median plane PML, the wire44runs parallel to the longitudinal median plane PML and within the width L34of the traversing passage34.

Thus, with the thickness E10of the seatbelt10situated within the height H34of the traversing passage34and its width L10situated within the width L34of the traversing passage34, the wire44moves within the height H34of the traversing passage34and touches the entire width L10of the seatbelt10when it is led from its passive position to its active position, which favours the cutting of the seatbelt10.

Given said positioning of the wire44within the width L34of the traversing passage34, it follows from this that the wire-strainers541,542, the low melt elements481,482and the stops501,502are mounted on each side of the width L34of the traversing passage34.

Still with the objective of improving the cutting of the seatbelt10by the wire44, the upper surface78of the traversing passage34takes the form of a cutting plane PC visible inFIG. 6and towards which the wire44goes when it moves from its passive position to its active position.

Said cutting plane PC makes it possible to prevent the belt10from escaping under the ascent of the wire44when it is heated, and, with the contribution of the stops501,502, said cutting plane PC makes it possible to ensure that the wire44positions itself largely within the thickness E10of the seatbelt when it is heated and that it carries out the cutting.

Preferably, said cutting plane PC allows the belt10to be maintained largely in the horizontal median plane PML in which the wire44is situated in active position.

Advantageously, the transversal joint52makes it possible to press, and even to compress, the belt10against the upper surface78when the casing32is closed and assembled.

In greater detail, at the definitive closing of the casing32, the belt10is gripped between the transversal joint52and the upper surface78, and the transversal joint52deforms so as to create pressure uniformly spread out over the belt10.

Owing to said deformation and said pressure of the joint52, the belt10is largely immobilised in the casing32, and the casing32remains movable and adjustable in position on said belt10.

Since the case32is broken down into two upper and lower halves80,82, assembled one against the other along their peripheral edges, the cutting plane PC is constituted by the lower surface84of a block86integral with the upper half80of the casing32, the central body62on which are mounted the wire44, the wire-strainers541,542, the low melt elements481,482and the stops501,502being integral with the lower half82of the casing32.

In order to limit the transfer of heat from the wire44in active position to the block86, and thus to the upper half80of the casing32, the cutting plane PC is crossed by a groove88situated opposite the wire44.

Said groove88is preferably wider than the wire44, and said groove88is implemented in the entire thickness E86of the block86and throughout its width L86likely to touch the wire44in active position.

In addition, and still in order to limit the transfer of heat from the wire44to the upper half80of the casing32, the cutting plane PC includes recesses of material90on each side of the groove88.

At the same time, and as illustrated byFIGS. 4 to 6, the block86includes lateral notches921and922in which the low melt elements481,482and the stops501,502are housed, said low melt elements481,482and said stops501,502being maintained in the notches921and922by the wire44when the two upper and lower halves80,82of the casing32are assembled one against the other.

According to the invention, the means of heating46the wire44are electrical and autonomous.

By autonomous, the invention means that said method of heating46have their own electric power supply, independent of the electric power supply of the vehicle.

For this purpose, said means of heating46include a battery94, visible inFIG. 3, installed in the lower half82of the casing32, next to the cutting means42.

In order to supply the wire44, the battery94is connected to the wire44through the wire-strainers541,542, and more specifically through pods961,962provided on the wire-strainers and in which the ends56,58of the wire44are set.

Of course, control means are provided in order to supply electricity to the wire44with the battery94only when the belt10must be cut.

Since the wire44is preferably made of stainless steel, the invention provides for supplying electricity, and thus heating the wire44, for at least 25 seconds, which makes it possible to heat the wire44to a temperature of approximately 315° Celsius with a battery94capable of delivering approximately 6000 mAh.

With a wire44at such a temperature, it is ensured that the material of the seatbelt10, generally nylon-based, melts and retracts, which makes it possible to separate the belt10into two pieces M1and M2reliably.

Lastly, in a preferred method of construction of the cutting means42, the wire-strainers541,542, the central body62, the stops501,502and the pins661,662are made of metal, whereas the casing32is rather made of a plastic, i.e., a polymer-based material.

Eventually, the cutting mechanism30according to the invention could also be used on a seatbelt10located somewhere else than in a vehicle and, for example, used to maintain a user's body on a machine, or on a safety harness.