The invention concerns caps for obturating a filler pipe head, in particular for the filling of a fuel tank, for example for vehicles, and more particularly the caps of this type which comprise a torque limiting device.

The invention also concerns torque limiting devices in general.

Caps of the aforementioned type are already known which comprise a cylindrical base adapted to obturate the filler pipe head and a top for gripping adapted to maneuver the base between an open position and a closed position of the cap in that filler pipe head.

The base comprises an interior space having a series of annularly disposed detents.

The top comprises a cylindrical barrel adapted to be partially inserted into the interior space of the base.

The top also comprises a finger slidably mounted on the barrel in a radial direction, and a spring disposed between the barrel and the finger to exert an elastic return force on that finger biasing it towards a position in which the finger projects to the exterior of the barrel.

The finger is adapted to be accommodated between two successive detents of the base to link the cap and the base in rotation, and thus to enable the base to be rotationally driven when the gripping top is rotated, so long as a torque less than a predetermined torque limit is applied between the top and the base.

If the torque becomes greater than the torque limit, the finger slides against the force exerted by the spring until the coupling between the finger and the series of detents ceases, thus rotationally disconnecting the top and the base.

This makes it possible not to over-tighten the cap in the filler pipe head. When the applied torque ceases or becomes less than the torque limit, the spring returns the finger; and the top and the base are again rotationally joined when the finger is accommodated between the following detents.

This known cap has the drawback of comprising several parts to assemble to form a torque limiter, and more particularly on the top.

This same drawback is to be found in the torque limiting devices for applications other than a cap, for example for an electric screwdriver head.

There is a need to mitigate the aforementioned drawback. According to a first aspect, the invention is directed to providing a torque limiting device that is simple, convenient and economic.

The invention thus relates to a torque limiting device comprising:

- a first member,

- a second member, and

- disengageable coupling means adapted to rotationally link the first and second members when a torque less than a predetermined torque limit is applied between those members in a determined direction of rotation, and to disengage the link between the members when a torque greater than the predetermined torque limit is applied between those members in the determined direction of rotation, those disengageable coupling means comprising a series of annularly disposed detents on the first member, and comprising an engagement mechanism on the second member, this engagement mechanism comprising a radially oriented moveable finger, and a spring for elastic return of the finger, which is adapted to be accommodated between two detents, each finger and each detent respectively comprising a first and a second inclined contact face forming ramps adapted to be in contact when a torque less than the predetermined torque limit is applied between the members in the determined direction of rotation,

the engagement mechanism further comprising an elastically deformable arcuate bridging member from which projects said finger, said arcuate bridging member and said finger being in one piece. The elastically deformable arcuate bridging member merges into the second member via two ends of said elastically deformable arcuate bridging member.

Thus, in the torque limiter according to the invention, the guide mechanism of the finger and the spring are produced from a single piece formed by the elastically deformable arcuate bridging member, which arcuate bridging member moreover forms a single piece with the finger.

The number of parts necessary to form the torque limiting device according to the invention is thus particularly reduced.

According to a particularly advantageous example embodiment of the invention, the second member is a one-piece plastic molding.

According to an example embodiment of the invention, each finger and each detent respectively comprises a third and a fourth contact face which are straight and adapted to be in contact when a torque is applied between the members in an opposite direction to the direction of rotation so as to rotationally link the first and second members.

Preferably, the engagement mechanism comprises two said fingers. According to an example embodiment of the invention, the elastically deformable arcuate bridging member comprises two pillars that merge into the second member and an arch linking the two pillars.

Furthermore, the elastically deformable arcuate bridging member is preferably curved like the series of detents.

If desired, the device comprises two diametrically opposite engagement mechanisms.

According to a second aspect, the invention relates to a cap to put in place by rotating it in a filler pipe head, in particular for the filling of a fuel tank, for example for vehicles, comprising a torque limiting device as described above.

According to an example embodiment of the invention, the first member is formed by a base adapted to obturate the filler pipe head, and the second member is formed by a gripping top adapted to maneuver the base between an open position and a closed position of the cap in the filler pipe head.

If desired, the top comprises a cylindrical barrel into which the elastically deformable arcuate bridging member merges.

According to an example embodiment of the invention, the base comprises an interior space in which is disposed a crown comprising the series of detents, and this interior space is adapted to receive the barrel of the top at least partially.

The disclosure of the invention will now be continued with the description of an example embodiment, given below by way of illustrative but non-limiting example, with reference to the accompanying drawings, in which:

- Figure 1 is front view of a cap in accordance with an embodiment of the invention and of a filler pipe head shown in cross-section;

- Figure 2 is an exploded perspective view of that cap;

- Figure 3 is a perspective view in the assembled state;

- Figure 4 is the cross-section view on IV-IV of Figure 1 ; and

- Figure 5 is an enlargement of a part of Figure 4.

Figures 1 and 2 illustrate a screw cap 1 , respectively in the assembled and dismantled states, for a filler pipe head 2 for the filling of a fuel tank (not shown), for example for vehicles (not shown).

This cap 1 comprises a gripping top 10, a base 30 and a fluid-tight seal 7.

The gripping top 10 comprises a gripping handle 1 1 for grasping the cap 1 in the hand, a cylindrical skirt 12, and two shoulders 13 and 14 extending on each side of the handle 1 1 towards the cylindrical skirt 12 to connect the skirt 12 to the handle 1 1 .

As visible in Figure 2, the top 10 comprises latching lugs 16 on an annular inner surface 17 of the skirt 12.

The top 10 further comprises a hollow cylindrical barrel 18 extending longitudinally on the opposite side to the handle 1 1 . The barrel 18 comprises a free end 19 and has on a lateral wall 20 in the vicinity of that free end 19, two elastically deformable arcuate bridging members 22 disposed diametrically opposite each other.

Each elastically deformable arcuate bridging member 24 has two ends merging into the barrel 18.

Here, each elastically deformable arcuate bridging member 22 comprises two pillars 23 merging into the lateral wall 20 of the barrel 18, and an arch 24 linking the two pillars 23 (see more particularly Figure 5).

A space is thus present between the arch 24 and the lateral wall 20 of the barrel 18.

The top 10 further comprises two fingers 25 which project from each arch 24, these fingers 25 being transversely oriented to the barrel 18.

Each finger 25 has the general shape of a trapezoidal tooth and has a face 26 inclined relative to the direction of the finger 25, and a straight face 27, in other words parallel to the direction of the finger 25, this inclined face 26 and straight face 27 being opposite faces.

The top 10 is a one-piece plastic molding.

The cap 1 further comprises a cylindrical base 30 comprising a lower portion 31 provided with several shoulders 32 in steps and an aperture 33.

The widest shoulder 32 joins to a threaded portion 35 having four recesses 36, visible in Figure 2.

Thus, the threaded portion 35 is divided into four sectors regularly spaced around the base 30, two successive sectors being separated by a recess 36.

The threaded portion 35 also joins to an annular groove 37 around the base 30.

This groove 37 joins to a collar 38 comprising four vent holes 39 regularly spaced on the periphery of the collar 38.

As is also visible in Figure 3, the base 30 further comprises an annular cavity forming an interior space 40, in which an annular crown 41 extends provided with a series of detents 42 extending transversely in the interior space 40. The crown 41 joins to a cylindrical interior wall 45 of the base 30 by four connecting arms 44 (which can be better seen in Figure 4).

Each detent 42 has the general shape of a trapezoidal tooth and has an face 46 inclined relative to the direction of the detent 42, and a straight face 47, in other words parallel to the direction of the detent 42, this inclined face 46 and straight face 47 being opposite faces, as can be seen in Figure 4.

As can be seen in Figure 1 , the filler pipe head 2 comprises a tubular body 3 comprising an aperture 4, a threaded portion 5, and an upper edge 6.

The annular fluid-tightn seal 7 (Figure 2) is adapted to be positioned on the cap 1 , against the edge 6 of the filler pipe head 2.

As visible in Figure 3, the fluid-tight seal 7 has a curved profile adapted to engage in the groove 37 of the base 30.

This seal 7 provides fluid-tightness between the cap 1 and the edge 6 of the filler pipe head 2.

As can be seen in Figure 3, the skirt 12 of the top 10 covers the collar 38 of the base 30, as well as its groove 37 provided with the seal 7.

The collar 38 is locked against axial translation by the latching lugs 16 of the top 10.

The threaded portion 35 and lower portion 31 project from the top 10. The barrel 18 of the top 10 is partially inserted into the interior space

40 of the base 30.

The arch 24 of each elastically deformable arcuate bridging member 22 is curved like the series of detents 42 on the crown 41 .

The fingers 25 of the elastically deformable arcuate bridging members 22 are accommodated in hollows formed between the successive detents 42 of the crown 41 .

The four vent holes 39 enable an air circuit to be created between the exterior of the cap 1 and the interior of the tank when the cap 1 is fixed to the filler pipe head 2.

The flow of air under pressure in the tank passes first of all via a vent valve (not represented) situated in the lower portion 31 of the base 30, then into the interior space 40 of that base 30 by a first zone comprising the elastically deformable arcuate bridging members 22 and the series of detents 42, then by a second zone in the vicinity of the seal 7, so that this stream of air under pressure lastly escapes to the outside via the holes 39.

The stream of air at reduced pressure follows the opposite path. The threaded portion 35 of the base is adapted to cooperate with the threaded portion 5 of the filler pipe head 2 to obturate it.

The cap 1 comprises an integrated torque limiter to prevent over- compressing and deteriorating the seal 7 which provides the fluid-tightness between the filler pipe head 2 and the cap 1 .

A description will now be made of the operation of the cap 1 with integrated torque limiter, with reference to Figures 4 and 5.

The fingers 25, which are radially oriented, are moveable against an elastic return force exerted by the arcuate bridging members 22 on which they are situated.

In resting position, the pillars 23 and the arch 24 of each arcuate bridging member 22 are not deformed.

When the gripping top 10 is maneuvered by a user in a locking direction V of the cap 1 to make it pass from an open position to a closed position of the cap 1 in the filler pipe head 2, a torque is applied between the top 10 and the base 30.

The inclined face 26 of each finger 25 of each arcuate bridging member 22 comes to bear against the inclined face 46 of a detent 42 of the crown 41 , and the top 10 rotationally drives the base 30 in the locking direction of the cap 1 , until the cap 1 attains its closed position in the filler pipe head 2.

During this maneuver, the fingers 25 are engaged in the hollow between the detents 42, and the arcuate bridging members 22 are still in their resting position, in which the pillars 23 and the arch 24 do not deform, or almost not so.

When the user continues the maneuver of the top 10 in the same direction of locking and the value of the torque applied between the top 10 and the base 30 does not exceed a predetermined threshold corresponding to a torque limit, the inclined faces 26 and 46 forming ramps cause the arcuate bridging member 22 to be subjected to a force tending to bring it towards the barrel 18, which force becomes greater than the deformation threshold of the arcuate bridging member 22, such that arcuate bridging member 22 deforms and the teeth 23 slide over the detents 42, the top 10 thus being able to turn without causing the base 30 to turn.

When the torque ceases or becomes less than the limit torque, the arcuate bridging member 25 returns to its original shape, which enables the fingers 25 to re-engage in the hollows between the following detents 42.

Thus, the inclined face 26 of each finger 25 moves until the following detent 42 is reached in the locking direction V, and so forth, until the value of the torque applied between the top 10 and the base 30 becomes less than the threshold value.

In this way, the tightening of the cap 1 in the filler pipe head 2 is performed simply in a way that is optimal and made safe.

When the gripping top 10 is maneuvered by the user in an unlocking direction D of the cap 1 to make it pass from the closed position to the open position of the cap 1 in the aperture 4, a torque is applied between the top 10 and the base 30.

The straight face 27 of each finger 25 of each arcuate bridging member 22 abuts against the straight face 47 of a detent 42 of the crown 41 , and the top 10 rotationally drives the base 30 in the unlocking direction of the cap 1 , until the cap 1 attains its open position, and can be removed from the filler pipe head 2.

Whatever the case, the value of the torque applying between the top 10 and the base 30 does not matter, so long as it is sufficient to commence the unlocking, there is no risk of the straight faces 27 and 47 disengaging.

Thus, the unlocking of the cap 1 of the filler pipe head 2 is ensured in a simple manner.

The top 10 comprises two fingers 25 which project from each arcuate bridging member 22 to provide robustness for the torque limiter, produced from plastic material.

Numerous variants are possible according to circumstances. For example, the top may only comprise a single finger which projects from a single arcuate bridging member.

In a variant not illustrated, the base comprises a continuous threaded portion around said base, in other words the base does not comprise the recesses 36 visible in Figure 2.

In another variant not illustrated, the base does not comprise any connecting arm between the crown and the cylindrical wall of the base.

In still another variant, the base does not comprise any vent hole, nor aperture of the type of aperture 33 visible in Figure 2.

By way of a further example, the cap and the filler pipe head may be fixed together via a bayonet type mounting instead of screwing.

According to another example embodiment of the invention, the cap may be locked into the filler pipe head. For this, a lock cylinder is accommodated in the barrel of the top.

As a variant, the cap cannot be locked in the filler pipe head.

In a variant not shown, the torque limiting device (arcuate bridging member such as 22, teeth such as 25 and detents such as 42) forms part of an assembly different from a cap, for example a screwdriver head.

It should be noted more generally that the invention is not limited to the examples described and represented.