EP2362835B1 - Writing implement, and cap with inner grooves for a writing implement - Google Patents

Description

TECHNICAL FIELD OF THE INVENTION

The present invention relates to writing instruments such as ink pens, and in particular to writing instruments comprising a writing body extending from an end having a writing tip integral with the writing body, and a removable cap covering the writing tip in a coupling position of the cap with the writing body, said cap having a bottom, a tubular wall extending along a central axis between a first end of junction with the bottom and a second end defining an axial opening, said tubular wall having an inner surface on which protruding reliefs are adapted to retain the cap by engagement with the writing body in the coupling position.

BACKGROUND OF THE INVENTION

A writing instrument of the above kind, such as a ballpoint pen, can store an aqueous ink or any conventional ink. The cap prevents excessive drying of the tip by covering it during periods of nonuse of the instrument. Sealing with respect to the outside may be achieved by annular contact of the tubular wall of the cap on one end of the writing body adjacent to the writing tip. In some cases, the cap has an internal cap that covers only the writing tip.

However, when coupling the body of the writing instrument with the cap, the air at the inside of the cap is compressed, thus generating an increase in the internal pressure of the cap, sometimes detectable by some users. When the cap is loosened, the air pressure inside the cap is suddenly lowered, which causes a discharge and pumping of the ink. Since the cap is alternately coupled with and detached from the body of the writing instrument during normal use, a significant amount of ink can be moved and risk being wasted, for example by being trapped in the baffles of the writing instrument. a venting cavity. The inventors have noted that this phenomenon can be sensitive in all cases where a liquid ink is used, whether in a free ink tank, but also in the case of liquid ink stored in a fibrous buffer.

One solution for balancing the internal pressure in the cap is to drill a hole opposite the opening. The document US5441356 thus provides a passage of air to avoid pressurizing the inside of the cap when placed on a pen body. This passage is formed at the bottom of the cap and closed by a shutter valve associated with a spring. With this kind of device, air can come out through the hole just before coupling and the spring closes the air passage when the cap is fixedly fixed on the pen body. The holding in closed position is guaranteed by the engagement of several internal projections point of the cap with an annular bead formed on the outer periphery of the pen body.

A disadvantage of this type of writing instrument is the complexity of the shutter system which requires several parts including a spring. The assembly of cap is then more expensive, which limits the attractiveness of the pens including such a system.

He is also known, by the document US 5911534 the use of a cap having longitudinal ribs and an annular bead projection sufficiently close to the bottom of the cap to engage with a portion of the writing body near the tip and distinct from the defined gripping zone by an elastic sleeve.

GENERAL DESCRIPTION OF THE INVENTION

The present invention aims to provide a writing instrument to prevent ink loss during coupling operations and detachment of the cap, and which is simple in design.

For this purpose, the writing instrument according to the invention is characterized in that the inner surface of the cap has at least one groove arranged between two of said reliefs and extending to the second end of the tubular wall.

Thus, it is obtained through the groove which extends to the second end a flow of air accumulated at the bottom of the cap towards the opening of the cap during a closing operation. The groove is used as an air gap between the cap and the writing body. This prevents the pressurization of the cap during its introduction or depression during removal, the groove or grooves ensuring a pressure equalizing function. In addition, this arrangement does not interfere with the retention of the cap and the bottom of the cap can be designed in a simple manner.

In another feature, the writing instrument comprises a sealing member integral with the cap, arranged between said at least one groove and the first end of the cap. The sealing member comprises for example an annular rib formed on the inner surface of the cap, at a distance from said first and second ends, said at least one groove extending to a central zone of the cap and in the vicinity of the rib annular. Thus an annular sealing contact can be obtained with the rib in the coupling position, so as to prevent drying of the writing tip. The close position of the groove with respect to the annular rib intended for the sealing contact makes it possible to evacuate via the groove all the surplus air accumulated at the bottom of the cap at the moment of penetration of the writing end of the groove. instrument in the hood.

According to another feature, the writing body comprises a free ink cartridge, the cartridge including a reservoir and an internal cavity arranged between the writing tip and the reservoir, the cavity being in communication with the reservoir and communicating directly with the reservoir. outside through an opening open on the outside of the writing body, said cavity being adapted to absorb an ink effusion. This avoids leakage when using ink systems sensitive to pressure variations and the presence of the grooved cap (s) further limits any ink movements during the removal phase of the cap. According to another feature, at least two grooves are provided on the inner surface of said tubular wall, which has an alternation between said reliefs and grooves. Preferably, the reliefs are at least three in number and distributed in a circular manner, the number of grooves being equal to the number of said reliefs. Each of the grooves extends in a general direction parallel to the central axis and the set of grooves defines at the axial opening the vertices of a regular polygon. With this distributed arrangement, the air can escape easily, regardless of the possible relative inclination between the cap and the body of the writing instrument during the introduction of the cap.

According to another feature, each of the grooves is adjacent to and separates two of said reliefs. Thus, the arrangement of the depressions and protrusions in the circumference of the cap makes the retention very effective while optimizing the pressure equalizing effect during the introduction of the cap. In an annular zone of the cap where the reliefs are distributed, the reliefs and the grooves may then occupy more than half of the internal circumference of the cap, for example at least 75% of this inner circumference.

According to another feature, the distance of the groove or grooves with respect to the sealing member is between 0.1 and 0.5 mm. Thus, the end of the grooves is as close as possible to the sealing zone of the cap. Because of the arrangement of the grooves (the length of which may be 40% or more of the depth of the cap), the volume of air that can be evacuated by the grooves is larger and the compressed air at the bottom of the cap can escape throughout the insertion of the writing body into the cap, even in the case where the gripping portion of the writing body is closely surrounded by the cap. Too great a proximity is however avoided so as not to cause a non-uniform deformation of the sealing member.

According to another feature, the writing body has a cylindrical gripping surface adjacent to the writing tip, this gripping surface having an annular protruding bead for cooperating with said reliefs, the projecting bead being arranged opposite to the writing tip to allow complete recovery of said gripping surface by the cap. The reliefs are then arranged near said second end.

Thus, the retention by the reliefs, preferably close to the opening of the cap, corresponds to an attachment with a contact of material, for example plastic-plastic, which occurs at the end of the introduction of the cap, when the majority of the air initially contained in the hood has evacuated. The grooves are elongate and hollowed into a cap which typically has a length of more than 2 cm, preferably more than 4 cm, so as to cover the gripping portion of the writing body used during writing.

According to another feature, the outer surface of the tubular wall of the cap is smooth at least on the side of said second end, the cap having a circular section in cross section. The cap thus has an easy grip and has a surface without edge, more pleasant to the touch. There is therefore a difference in shape between the smooth outer surface and the inner hollowed surface. The thickness of the cap remains thin and can vary for example between a maximum of the order of 1 mm and a minimum of the order of 0.6 mm. The cap may thus have at each of the grooves a thickness of between 40% and 70% of the overall thickness of the cap.

According to another feature, the writing body has an annular shoulder with an axial face in contact with the second end of the cap in the coupling position. Thus, the writing instrument with the closed cap externally has a usual appearance, the shoulder on which rests the cap to seal at least partially digs formed inside the cap.

In another feature, the writing body comprises a cartridge and a barrel partially covering the cartridge opposite said writing tip, the cartridge having a male thread for fixing the barrel, said shoulder being formed by an end of said barrel. Thus, a barrel typically without external relief and pleasant handling for the user can advantageously be disposed in the extension of the cap and close the outlet of each of the grooves.

BRIEF DESCRIPTION OF THE DRAWINGS

• la figure 1 est une vue suivant une première coupe longitudinale d'un corps de capuchon selon un mode de réalisation préféré de l'invention ;
• la figure 2 est une vue du corps de capuchon de la figure 1, suivant une deuxième coupe longitudinale ;
• les figures 3A et 3B représentent respectivement un premier détail et un deuxième détail de la paroi tubulaire du corps de capuchon illustré à la figure 2 ;
• la figure 4 est une vue éclatée représentant une cartouche et le fût associé constituant le corps d'un stylo pouvant coopérer avec un capuchon selon l'invention ;
• la figure 5 est une vue éclatée représentant des éléments constitutifs d'un capuchon conforme à l'invention ;
• la figure 6 est une vue axiale de l'ouverture du capuchon des figures 1 et 2 ;
• les figures 7 et 8 illustrent la position d'accouplement du capuchon avec le corps de stylo.

Other features and advantages of the invention will become apparent from the following description of several embodiments, given by way of non-limiting examples, with reference to the accompanying drawings in which:

• the figure 1 is a view along a first longitudinal section of a cap body according to a preferred embodiment of the invention;
• the figure 2 is a view of the hood body of the figure 1 following a second longitudinal section;
• the Figures 3A and 3B respectively represent a first detail and a second detail of the tubular wall of the cap body illustrated in FIG. figure 2 ;
• the figure 4 is an exploded view showing a cartridge and the associated barrel constituting the body of a pen that can cooperate with a cap according to the invention;
• the figure 5 is an exploded view showing components of a cap according to the invention;
• the figure 6 is an axial view of the hood opening Figures 1 and 2 ;
• the Figures 7 and 8 illustrate the coupling position of the cap with the body of pen.

DESCRIPTION OF THE PREFERRED EMBODIMENTS OF THE INVENTION

In the various figures, identical references indicate identical or similar elements. The writing instrument 1 makes it possible to write by any writing, erasing or highlighting medium, hereinafter referred to as ink.

With reference to Figures 1, 2 , 4 and 5 , the writing instrument 1 comprises a writing body 10 and a removable cap C adapted to cover one or other of the ends (10a, 10b) of the writing body 10 in a coupling position. A writing tip 11 is mounted at one of the ends (10a, 10b) of the writing body 10. By way of non-limiting example, the writing body 10 may comprise a tubular piece 12 made of plastic, which contains a reserve of ink 13 and accommodates an ink supply device 14 supporting the writing tip 11.

In the embodiment of the figure 4 , the tubular piece 12 with the ink reserve 13, the ink supply device 14 and the writing tip 11 define a cartridge 15. The cartridge 15 fits into a drum 16 and can be permanently connected. or removable to this barrel 16. In the example of the figure 4 , the attachment is removable and can be achieved by means of a male thread 17 formed externally on the tubular part 12 of the cartridge 15. The barrel 16 may comprise a female thread formed on an inner wall thereof, so that the barrel 16 and the cartridge 15 can be removably attached to each other. It is understood that a spare cartridge can then be inserted into the drum 16 when the ink is emptied. The mode fixing may be of different nature, such as for example and not limited to a fixing by force-fitting contact, snap-fastening. A chemical bond or an ultrasonic bond may also be provided, the cartridge 15 being no longer separable from the barrel 16 in this case. Alternatively or in addition, the writing instrument 1 may comprise a detachable reservoir containing a reserve of ink 13. This reservoir is fixed in this case to the rear of the cartridge 15.

As illustrated in figures 5 , 7 and 8 , the writing instrument 1 comprises a cap C adapted to cooperate with the writing body 10. The cap C may have a tubular cap body 20, an inner cap 21 and a clip 22, and an insert 23 at one end 20a of the cap C to permanently attach the clip 22 to the cap body 20. The inner cap 21 serves to prevent drying of the tip 11. It can of course be removed in some embodiments of the cap C. L axial opening 24 of the cap C has an inside diameter substantially corresponding to the outside diameter of the gripping portion 30 of the writing body 10. This gripping portion 30 may be cylindrical or in another form adapted to a grip between the thumb and the index during a write operation. In the non-limiting example of figures 4 , 7 and 8 the gripping portion 30 is integral with the cartridge 15.

In a preferred embodiment of the invention, the body 20 of the cap C has reliefs 31 which protrude and are able to engage with the writing body 10 when the cap C is in the coupling position. As is visible on the Figures 1 and 2 , the reliefs 31 may be distributed annularly near the axial opening 24 of the cap C. These reliefs 31 are formed for example by projections projecting radially towards the central axis Z of the cap C. The tubular wall 32 of the cap body 20 also has on its inner surface one or more grooves 33 hollowed out in the thickness. of the cap body 20. These grooves 33 extend axially between a central region M of the cap C and the end 20b where the opening 24 of the cap C is formed. Each of the grooves 33 is arranged between two adjacent protruding projections 31. The section of each groove 33 may correspond to a "U", with a flared U shape for example as illustrated in FIG. figure 6 . The end of the grooves 33 opposite the opening 24 may have a decreasing depth. In other words, the digging of the grooves 33 can be made with lateral slopes and a slope opposite the opening 24. The variation in thickness is not too sudden. This form of groove avoids slits or visible marks from outside the cap C, especially when the wall is thin.

With reference to figures 4 , 7 and 8 , the gripping portion 30 of the writing body 10 has a cylindrical surface with an annular bead protruding B to cooperate with the reliefs 31. The annular bead B is here disposed opposite the writing tip 11 to allow a full cover of the gripping portion 30 by the cap C. Alternatively, fastening means adapted to cooperate with the reliefs 31 may have a different form of an annular bead, for example and without limitation one or more forms each extending less than half the circumference of the gripping portion 30.

It will be clear from the figure 8 that the commitment of the punctual reliefs is made when the cap C reaches its closed position by creating a snap. In this position, the reliefs 31 thus retain the cap C on the writing body 10 so that the cap C can not leave the writing body 10 without an action of the user. As soon as the user disengages the reliefs 31 of the annular bead B, the withdrawal is then particularly easy.

With reference to Figures 1 and 2 optionally, the tubular wall 32 of the cap body 20 also has on its inner surface an annular rib 34 or similar projection which is intended to seal an interior volume of the cap C located at the bottom 35 of the cap when the cap C is fitted on the writing body 10. The grooves 33 extend away from the bottom 35, between the outlet of the cap C and a level adjacent to the annular rib 34. The position of this annular rib 34 is for example close or merged with a transverse median plane of the cap C, and is more generally distant from the ends 20a, 20b of the cap body 20.

As is visible on the Figures 1, 2 , 3A , 7 and 8 , the annular rib 34 formed inside the cap body 20 allows a confinement of the volume V of air near the bottom 35 by preventing this air from escaping outwardly when the cap C is in the fully coupled position. The grooves 33 exert a pressure-balancing function during the insertion of the writing body 10 into the cap C, until the moment before the contact of the annular bead or rib 34 with the writing body 10. This contact is made with friction and may occur just before or at the same time as the latching of the writing body 10 by the reliefs 31 salient. So at most later when the reliefs 31 are engaged on the annular bead B of the writing body 10, sealing is provided for the volume V of air enveloping the writing tip 11. Figures 7 and 8 illustrate the central zone M where the sealing barrier can typically be formed.

The grooves 33 do not hinder the relief of the relief function 31 because of their positioning, alternating with the reliefs 31. Each of the grooves 33 thus extends in a general direction parallel to the central axis Z. Each of the grooves 33 is a passage allowing air accumulated near the bottom 35 of the cap C to escape through the wide axial opening 24. Without limitation, the number of grooves 33 may be greater than or equal to three. In the embodiment of the figure 6 six grooves 33 are formed in the thickness of the tubular wall 32 of the cap body 20. These grooves 33 thus form, at the axial opening 24 of the cap C, the vertices of a regular hexagon. Naturally, the angular spacing between the grooves may be different from 60 °.

With reference to figures 1-2 and 6-8 illustrating the inside of the cap C, the reliefs 31 are distributed in a circular manner. The cap has in the illustrated example a circular section. There exists in this case an imaginary circle in contact with all the reliefs 31 which is in a transverse plane, preferably perpendicular to the Z axis and of diameter D1 strictly less than the diameter D2 of the annular bead B. The reliefs 31 and the grooves 33 extend for example at least 75%, preferably at least 90%, of the inner circumference of the cap C. On the Figures 1 and 2 each grooves 33 separates two adjacent reliefs 31. The spacing between two successive reliefs 31 may thus correspond substantially to the width of a groove 33.

The outer surface of the tubular wall 32 is preferably smooth, at least on the side of the opening 24 of the cap C. More generally, no slot or similar longitudinal relief appears opposite the grooves 33 and these are entirely arranged internally in the cap C. The absence of asperity on this wall 32 makes the entry of the writing instrument 1 more pleasant to the touch for the user. The barrel 16 of the writing instrument 1 can cooperate with the cartridge 15 and come to be positioned vis-à-vis the outlet of the grooves 33, as illustrated in FIGS. Figures 7 and 8 . For example, the shaft 16 may have an outer diameter substantially equal to the outer diameter of the cap C, or slightly lower, while closing the outlet of each of the grooves 33.

In an optional embodiment, a seal within the cap C may be provided by a sealed annular contact between the barrel 16 and the end 20b of the cap body 20. To achieve this, a sealing liner or joint (not shown) may optionally be attached or attached to the end of the barrel 16 close to the gripping portion 30 of the writing body 10. This seal may supplement or replace the sealing performed by the annular rib 34. It will be understood that the seal inside the cap C can thus be obtained by a sealing contact between the annular edge at the end 20b of the cap C and a shoulder 40 of the writing body 10. This annular shoulder 40 with a axial face which is here in contact with the second end 20b of the cap C in the coupling position can alternatively simply serve to extend the cap C and at least partially close the outlet of the grooves 33, without the contact is sealed. This shoulder 40 may be formed integrally with the cartridge 15 or by a ring.

In the example of Figures 7 and 8 , the cartridge 15 has a male thread 17 for securing the barrel 16 and a radial annular projection 45 in the vicinity of the thread 17. The annular projection 45 defines a stop for the barrel 16 completely screwed onto the cartridge 15. The barrel 16 plays then a stop role for the cap C when the reliefs 31 are engaged on the rear of the annular bead B, as shown in FIG. figure 8 . In an alternative embodiment, the axial stop of the cap C can be achieved at the level of the cartridge 15. As illustrated in FIGS. Figures 1, 2 and 8 The cap C may have an increase in its inside diameter on the side of the second end 20b. This allows an adaptation to the annular projection 45.

At each of the grooves 33, the thickness e2 may be between 40 and 70% of the overall thickness e1 of the cap C, as can be seen in the FIGS. Figures 6, 7 and 8 . The section height of the air passage can be maximized. In the case of a cap C formed by plastic injection, the remaining thickness e2 can be limited to about 0.6 mm this remaining sufficient thickness not to generate filling problem during the injection process. It is understood that only discontinuous portions of the annular bead B formed on the writing body 10 are in contact with the cap C when the latter is in the coupling position.

Without limitation, the cap C may have a length of the order of at least 2 cm and preferably at least 4-5 cm. The protruding projections 31 are close to the end delimiting the axial opening 24 of the cap C and the distance from the edge of the opening 24 represents for example from 10 to 25% of the length of the grooves 33. only at the end of stroke, during the coupling operation of the cap C, that the reliefs 31 engage on the annular bead B or any other fastener formed on the rear of the gripping portion 30 of the body It is understood that the length of the grooves 33 may correspond substantially to the length of the gripping portion 30 of the writing body 10, formed between the annular bead B or the like and the upper end of the tubular piece 12 where is fixed the writing tip 11. In the embodiment of the figures, the length is the same for the different grooves 33 and is at least 40% of the depth 50 of the cap C. More generally, the length of each groove 33 depends on the architecture of the writing body 10 and can also be adjusted according to the overall shape of the cap C.

The cartridge 15 illustrated at figure 4 may comprise a device 14 for supplying ink to the writing tip, which is associated with a cavity adapted to absorb an ink spill (not shown). The part of the cartridge 15 covered by the barrel 16 corresponds substantially to the ink tank and the cavity is arranged between the device 14 and this reservoir where the ink reserve 13 is stored. The ink supply device delimits, for example with the tubular piece 12 a cavity in communication with the reservoir. This cavity communicates directly with the outside through an orifice (not shown) open on the outside. With pressure balancing and the presence of such a cavity to absorb the ink spills, the risk of ink leakage becomes extremely low.

One of the advantages of the invention lies in the capacity of a cap C, typically long enough to cover a gripping portion 30 of the writing body 10, to evacuate the air confined inside and thus achieve a balance of pressure, without the design of this cap C causes congestion and / or assembly disadvantages.

In a variant not shown, the inner cap may have the shape of a cavity for receiving and including the writing tip 11. The cavity of the inner cap has an opening whose flange is plate on a contact generator on the end. of the writing body 10. This avoids the drying of the ink in the writing tip 11 without causing ink drop around the periphery of the tip 11. This avoids defiling the writing medium during use subsequent writing instrument 1.

Advantageously, the inner cap can then be mounted on a spring pushing the opening edge of the cavity of this inner cap against a radial shoulder of the writing body 10. The inner cap 21 may also be made of elastomeric material or have a flange coated with an elastomeric layer to seal the contact generator.

For writing bodies comprising a liquid ink reservoir connected to the outside by a baffle duct opening into the conical part of the writing body 10, it is useful for the cavity of the internal cap to also encompass the orifice exit of the baffle duct.

The presence of the grooves 33 of exhaust air is then particularly advantageous to avoid the pumping effect of the reservoir ink of the writing instrument 1.

It is understood that each of the forms and details of embodiment described above can be used alone or in combination. It should be obvious to those skilled in the art that the present invention allows embodiments in many other specific forms without departing from the scope of the invention as claimed. In particular, although the description mentions grooves 33 dug in the thickness of the cap C parallel to the central axis Z with a constant width, the skilled person can appreciate that any other form of longitudinal component channel is suitable to allow the escape of air through the opening 24 of the cap C when closing the cap C. It is understood that the groove or grooves 33 formed at the inner surface of the cap C may result from an arrangement of the C. For example, at least one groove 33 may be formed by a slot in an inner part of the cap C or by a spacing between different components of the inner surface of the cap C.

Claims (13)

1. Writing implement comprising a writing body (10) extending from an end (10a) having a writing tip (11) integral with the writing body, and a removable cap (C) covering the writing tip (11) in a coupled position of the cap with the writing body (10), said cap (C) having a bottom (35), a tubular wall (32) extending along a central axis (Z) between a first end (20a) joining with the bottom (35) and a second end (20b) defining an axial opening (24), said tubular wall (32) having an inner surface on which protrusions (31) are capable of holding the cap (C) by engagement with the writing body (10) in the coupled position, characterized in that said protrusions (31) only extend close to the second end (20b), so that the protrusions (31) can engage with a portion of the writing body (10) which is distant from the writing tip, by a contact which results on completion of fitting the cap and in that the inner surface of the cap (C) has at least one groove (33) arranged between two of said protrusions (31) and extending to the second end (20b) of the tubular wall (32), said groove further extending longitudinally toward the bottom (35) as far as an area remote from said protrusions (31).
2. Writing implement according to claim 1, comprising a sealing element integral with the cap (C), arranged between said at least one groove (33) and said first end (20a) of the cap.
3. Writing implement according to claim 2, in which the sealing element comprises an annular rib (34) formed on the inner surface of the cap (C), at a distance from said first and second end (20a, 20b), said at least one groove (33) extending to a median zone (M) of the cap and in proximity to the annular rib (34).
4. Writing implement according to claim 2 or 3, in which the distance of said at least one groove (33) in relation to said sealing element is comprised between 0.1 and 0.5 mm.
5. Writing implement according to one of claims 1 to 4, in which at least two grooves (33) are provided on the inner surface of said tubular wall (32), which alternates between said protrusions (31) and said grooves (33).
6. Writing implement according to claim 5, in which each of the grooves (33) is adjacent to and separates two of said protrusions (31).
7. Writing implement according to one of claims 1 to 6, in which said protrusions (31) are at least three in number and distributed in a circular fashion, the number of grooves (33) being equal to the number of said protrusions, each of the grooves (33) extending in a general direction parallel to the central axis (Z) and the set of grooves defining the apices of a regular polygon at the axial opening (24).
8. Writing implement according to one of claims 1 to 7, in which the writing body (10) has a cylindrical grip surface adjacent to the writing tip (11), this grip surface having a protruding ring-like projection (B) for cooperating with said protrusions (31), the protruding projection (B) being arranged opposite the writing tip (11) in order to allow said grip surface to be completely covered by the cap (C).
9. Writing implement according to one of claims 1 to 8, in which the outer surface of the tubular wall (32) of the cap (C) is smooth at least towards said second end (20b), the cap having a circular cross section.
10. Writing implement according to one of claims 1 to 9, in which the cap (C) has a thickness (e2) at the level of each of the grooves (33) comprised between 40% and 70% of the general thickness (e1) of the cap.
11. Writing implement according to one of claims 1 to 12, in which the writing body (10) has an annular shoulder (40) with an axial face in contact with the second end (20b) of the cap (C) in the coupled position.
12. Writing implement according to claim 11, in which the writing body (10) comprises a cartridge (15) and a barrel (16) partially covering the cartridge (15) opposite said writing tip (11), the cartridge (15) having a male thread (17) allowing the barrel to be fixed, said shoulder (40) being formed by one end of said barrel (16).
13. Writing implement according one of claims 1 to 12, characterized in that in an annular zone of the cap (C) where said protrusions (31) are distributed, the protrusions (31) and the grooves (33) occupy at least 75% of the inner circumference of the cap (C).

Images