ASSEMBLY FOR CLOSING A TUBE BY SCREWING A CAP ONTO A NECK, FEATURING MEANS FOR CENTERING THE CAP

Abstract

The invention relates to an assembly (16) for closing a tube (10), said assembly (16) comprising: - a neck (20) extending along a principal axis (A) to a free upper end edge (43), and having an external helical thread (32), - a cap (30) having an internal thread (40) complementary to the external thread (32) to allow the cap (30) to be screwed onto the neck (20), characterized in that it comprises means for centering the cap relative to the neck (20) during screwing, formed by at least one projection (46) extending from the thread root (32A) of one of the external or internal threads (32), a residual radial clearance (j1) remaining between the cap (30) and the neck (20) at the projections (46) in the screwed position of the cap (30) onto the Bottle neck (20). Figure for the abbreviation: Figure 5

Description

Title of the invention: ASSEMBLY FOR CLOSING A TUBE BY SCREWING A CAP ONTO A NECK COMPRISING MEANS FOR CENTERING THE CAP Technical field of the invention

[0001] The present invention relates to an assembly for closing a tube, said assembly comprising:

[0002] - a tube head comprising a main neck up to an end edge su free upper part, and comprising a helical external thread, the external thread having a thread root and a thread crest,

[0003] - a plug comprising an internal thread complementary to the external thread for allow the cap to be screwed onto the neck, the internal thread having a thread base and a thread top. Technical background

[0004] It is known to equip flexible tubes with a cap that allows them to be closed between two uses. This prevents the contents of the tube from spilling. It also prevents pollutants from entering the tube. However, such a cap alone generally does not guarantee perfect airtightness.

[0005] To ensure the airtightness of the tube before its first use, it is known to seal it by means of a cover which is glued to the open end of the neck. The cover makes it possible to keep the product contained in the tube airtight during its storage prior to its first use, which represents a very important part of the overall lifespan of the tube.

[0006] To allow a user to easily peel off the seal, it has a tab that is not glued to the neck. The tab protrudes radially from the neck to provide a grip for the user.

[0007] When the cap is first screwed onto the tube during production, the tab is folded back against the outer face of the neck so as to be interposed between an outer thread of the cap and an inner thread of the neck.

[0008] To allow the cap to be easily screwed onto the neck, a radial clearance is provided between the cap and the neck. This radial clearance also prevents the tab from being too tight between the cap and the neck.

[0009] However, it has been observed that in certain cases, an angular sector of the cap is found clamped on one side of the neck, while the diametrically opposite angular sector accumulates all of the radial play.

[0010] This problem appears particularly when the production rate of the tubes is very high. In this case, the cap is screwed onto the neck at high speed.

[0011] When the tab is pinched between the cap and the neck during screwing, it is rotated by the cap. This twisting movement damages the seal. At worst, the twisting of the seal causes it to tear or detach, making the seal no longer able to fulfill its sealing role. At best, unsightly folds form in the seal. This problem particularly occurs when the tube production rate is very high. The cooling time of the weld between the seal and the neck is then insufficient to withstand the torsional stress.

[0012] Furthermore, this uneven distribution of radial clearance between the cap and the neck is that the cap is generally tilted relative to the main axis of the neck. This results in an unsightly appearance of the tube thus obtained. In addition, when the cap is tilted, this can cause friction between a shoulder of the tube and an external skirt of the cap. Such friction leaves marks on the rubbing surfaces, causing an aesthetic defect and detachment of particles likely to pollute the environment.

[0013] Furthermore, such an unequal distribution of the radial clearance can result in the plug being damaged in the angular sector, accumulating all the radial clearance when the screwing torque required to ensure the tube is sealed is high.

[0014] Some containers already have a neck and a cap equipped with means for centering the cap relative to the neck. However, these centering means only allow the cap to be centered at the end of its screwing. In particular, this does not solve the problem posed by damage to the seal during screwing. Summary of the invention

[0015] The present invention provides an assembly for closing a tube, said assembly comprising:

[0016] - a tube head comprising a main neck up to an end edge su free upper part, and comprising a helical external thread, the external thread having a thread root and a thread crest,

[0017] - a plug comprising an internal thread complementary to the external thread for allow the cap to be screwed onto the neck, the internal thread having a thread base and a thread top,

[0018] characterized in that it comprises means for centering the cap relative to the neck during its screwing formed by at least one projection which extends from the bottom of the thread of one of the external thread or the internal thread and whose height is less than that of said thread, a residual radial clearance remaining between the cap and the neck at the level of the projections in the screwed position of the cap on the neck.

[0019] According to another characteristic of the assembly produced according to the teachings of the invention, the external thread or the internal thread comprises several projections which are distributed regularly around the main axis.

[0020] According to another characteristic of the assembly produced according to the teachings of the invention, there are four projections.

[0021] According to another characteristic of the assembly produced according to the teachings of the invention, each projection is arranged on the external thread of the neck.

[0022] According to another characteristic of the assembly produced according to the teachings of the invention, the cap and the neck are made of a rigid plastic material, such as HDPE.

[0023] According to another characteristic of the assembly produced according to the teachings of the invention, each projection has the same rigidity as the thread crest of the other among the external thread or the internal thread.

[0024] According to another characteristic of the assembly produced according to the teachings of the invention, each projection is in the form of a rib which axially connects two adjacent turns of the thread.

[0025] According to another characteristic of the assembly produced according to the teachings of the invention, at least one of the projections is arranged between the two upper end turns of the thread.

[0026] According to another characteristic of the assembly produced according to the teachings of the invention, it comprises a cover closing said neck, the cover having a radial gripping tab folded against the external thread of the neck, the radial tab being received in a nominal radial clearance between the upper end turn of the internal thread and the neck.

[0027] According to another characteristic of the assembly produced according to the teachings of the invention, the width of the projection, taken in the direction of the turn, is less than its height.

[0028] According to another characteristic of the assembly produced according to the teachings of the invention, the upper end turn of the internal thread has a height decreasing from bottom to top so that the nominal radial clearance between the thread crest of said end turn and the thread root of the external thread of the plug 30 is greater than the nominal radial clearance between the other turns of the internal thread and the external thread.

[0029] According to another characteristic of the assembly produced according to the teachings of the invention, the neck comprises a non-threaded upper end portion, said portion having a truncated cone shape.

[0030] The invention also relates to a tube comprising a closure assembly made according to the teachings of the invention.

[0031] The invention also relates to a tube head of said assembly. Brief description of the figures

[0032] Other characteristics, aims and advantages of the invention will emerge from the following description, which is purely illustrative and non-limiting, and which must be read in conjunction with the appended drawings briefly described below.

[0033] [Fig. 1] is a perspective view showing a tube comprising a closure assembly made according to the teachings of the invention comprising a cap screwed onto a neck.

[0034] [Fig.2] is a perspective view showing the tube of [Fig.l] which shows the neck of the tube of [Fig.l].

[0035] [Fig. 3] is an axial couple view along an axial section plane which represents a closure assembly produced according to the state of the art.

[0036] [Fig.4] is a larger-scale perspective view of the neck of the tube of [Fig.2] before it is fitted with its cover, the neck being produced according to a first embodiment of the invention.

[0037] [Fig.5] is an axial sectional view along section plane 5-5 of [Fig.1] which represents the cap screwed onto the neck produced according to the first embodiment of the invention.

[0038] [Fig.6] is a view similar to that of [Fig.6] in which the neck is produced according to a second embodiment of the invention. Detailed description of the invention

[0039] For the remainder of the description, elements having an identical structure or similar functions will be designated by the same reference.

[0040] For the remainder of the description, an axial direction will be adopted which corresponds in the figures to that of the main axis “A” of the neck of the closure assembly. Radial directions directed orthogonally to the axial direction by radiating from the main axis will also be adopted. Finally, a circumferential direction directed orthogonally to the axial and radial directions will be adopted.

[0041] Figures 1 and 2 show a tube 10 having a body 12 made of a tube of flexible and deformable material. The tube 10 comprises a closure assembly 16.

[0042] The closure assembly 16 comprises a tube head 18, more particularly visible in [Fig. 2], comprising a neck 20 which extends along a main axis “A”. The neck 20 has a tubular shape. It extends from a lower end 22 which is connected in a sealed manner with the body 12, to a free upper end 24 which has a central opening 26.

[0043] In the embodiment shown in the figures, the head 18 has a shoulder 28 which makes it possible to connect the neck 20 to the body 12. The neck 20 extends axially from the center of the shoulder 28. In a non-limiting manner, the neck 20 and the shoulder 28 are designed here in a single piece and are in continuity of material.

[0044] The neck is preferably made of a rigid plastic material, such as high density polyethylene (HDPE) or polypropylene (PP).

[0045] A user is likely to discharge the contents of the tube 10 through the central opening 26 by pressing the body 12.

[0046] The closure assembly 16 also includes a cap 30, notably visible in [Fig.l]. The cap 30 is intended to close the opening 26 by screwing onto the neck 20.

[0047] The neck 20 comprises an external helical thread 32 which extends in radial projection towards the outside from an external lateral wall 34 of the neck 20. The external thread 32 is here produced in a single piece in continuity of material with the neck 20.

[0048] The neck 20 here comprises a non-threaded upper end portion 20A comprised between a turn 32s of the upper end of the external thread 32, called the last turn 32s, and the upper edge 43.

[0049] The cap 30 comprises a cylindrical skirt 36 which extends axially downwards from a top radial wall 38 of the cap 30. A helical internal thread 40 projects radially inwards from an internal wall of the skirt 36. The internal thread 40 is complementary to the external thread 32 to allow the cap 30 to be screwed onto the neck 20.

[0050] The internal net 40 is here made in a single piece in continuity of material with the skirt 36.

[0051] The skirt 36 is made in a single piece and in the same material as the top wall 38. More particularly, in the embodiment shown in the figures, the plug 36 is made in a single piece in continuity of material.

[0052] The cap 30 is preferably made of a rigid plastic material, such as high density polyethylene (HDPE) or polypropylene (PP).

[0053] Preferably, the two threads 32, 40 are made of the same material.

[0054] Each thread 32, 40 has here, in a non-limiting manner, between two and three turns, for example 2.5 turns.

[0055] The external thread 32 of the neck 20 has a thread root 32A defined as being the root of the helical groove delimited between two adjacent turns of the external thread 32. The external thread 32 also has a thread crest 32B defined as being the free radial end helical edge of the external thread 32. Finally, a radial height “He” of the external thread 32 is defined as being the radial distance between the thread root 32A and the thread crest 32B.

[0056] Similarly, the internal thread 40 of the plug 30 has a thread bottom 40A defined as being the bottom of the helical groove delimited between two adjacent turns of the internal thread 40. The internal thread 40 also has a thread crest 40B defined as being the free radial end helical edge of the internal thread 40. Finally, a radial height “Hi” of the external thread 40 is defined as being the radial distance between the thread bottom 40A and the thread crest 40B.

[0057] By way of non-limiting example, the radial height “Hi” of the external thread 40 is equal to 0.8 mm.

[0058] The neck 20 is here equipped with a cover 42 which closes its central opening 24. The cover 42 has the shape of a disc whose periphery is fixed on an upper end edge 43 of the neck 20 forming a perimeter of the central opening 24, for example by gluing. The cover 42 is for example formed by a laminate sheet comprising a barrier layer to prevent the passage of air, such as a layer of aluminum. The thickness of the cover 42 is very thin, for example less than 100 μm, preferably of the order of 80 μm.

[0059] When the cap 30 has been screwed onto the neck 20, a face 44 of the top wall 38 is here axially clamped against the free end edge 43 of the neck 20 in order to enclose the periphery of the cover 42. This makes it possible to firmly hold the cover in the position of closing the central opening 24.

[0060] The cover 42 further comprises a radial gripping tab 42A which extends radially from an edge of the disc-shaped portion. The radial tab 42A has the same thickness as the disc-shaped portion of the cover 42. Before using the tube 10, the radial tab 42A is folded against the external face 34 of the neck 20.

[0061] In the embodiment shown in the figures, at least one zone of the radial tab 42A covers an angular sector of at least the upper end turn 32s of the external thread 32, as shown in [Fig.2].

[0062] In a variant of the invention not shown, the axial distance between the upper end edge of the neck and the upper end turn of the external thread is greater than the length of the radial tab. Thus, the radial tab of the cover is not in contact with the external thread when it is folded down.

[0063] To allow the screwing and unscrewing without friction of the cap 30 on the neck 20, a nominal radial clearance “jO” is provided between the external thread 32 of the neck 20 and the internal thread 40 of the cap 30. This nominal radial clearance “jO” must be sufficiently high to take into account the manufacturing tolerances of the neck 20 and the cap 30.

[0064] This nominal radial clearance “jO” here has a value determined at a free upper end of the neck 20. This nominal radial clearance “jO” is for example 0.27 mm. This nominal radial clearance “jO” also makes it possible to prevent the radial tab 42A of the cover 42 is not pinched between the external thread 32 and the external thread 40 during the operation of screwing the cap 30 onto the neck 20.

[0065] Thus, a portion of the tab is intended to be received in the nominal radial clearance “jO” between a turn 40s of the upper end of the external thread 40 and the neck 20.

[0066] Ideally, this nominal radial clearance “jO” should be distributed more or less equally all around the neck 20. However, it has been observed that in certain cases, the cap 30 could end up eccentric relative to the neck 20 to the point that one side of the cap 30 is completely tightened against the neck 20 while the nominal radial clearances “jO + jO” of the two opposite sides, i.e. here 0.54 mm, is accumulated on the diametrically opposite side, as shown in [Fig. 3]. On the tightened side, the external thread 32 is completely fitted into the internal thread 40 until the thread crests 32B 40B of each thread 32, 40 are in contact with the thread roots 40A, 32A of the other thread 40, 32.

[0067] When the tab 42A of the cover is completely clamped between the external thread 32 and the internal thread 40 during the screwing operation, it is driven in rotation with the cap 30 by friction. This induces a torsional torque in the cover 42, thus causing it to be damaged and / or detached from the edge 43.

[0068] Furthermore, even when the neck 20 is not equipped with a cover 42 or the radial tab 42A is not on the clamped side of the cap 30, this configuration causes the cap 30 to tilt, which is then inclined relative to the main axis “A” of the neck 20.

[0069] To solve these problems, the invention proposes to equip the closure assembly 16 with means for centering the cap 30 relative to the neck 20 during its screwing.

[0070] The centering means are formed by at least one projection 46 which extends radially from the thread root of one of the external thread 32 or the internal thread 40 to a free end.

[0071] In the embodiment shown in Figures 4, 5 and 6, only one of the threads, here the external thread 32, has projections 46, the other thread, here the internal thread 40, does not have any projections 46.

[0072] In a variant of the invention not shown, only the internal thread 40 comprises such projections 46.

[0073] According to another variant of the invention, not shown, the external thread 32 and the internal thread 40 both comprise such projections 46.

[0074] The external thread 32 comprises several projections 46 which are regularly distributed around the main axis “A”. For example, the projections 46 are at least three in number, preferably at least four in number.

[0075] The height “h” of the projection 46 is less than that of said external thread 32. This allows in particular that the projection 46 does not form a rotation stop of the cap 30 relative to the neck 20. This allows more particularly that the internal thread 40, which does not include the projections 46, can be engaged in the external thread 32 including the projections 46, so that the top 40B of the thread can slide against the projections 46. Thus, the projections 46 have a spacer function interposed radially between the two threads 32, 40 to guarantee a minimum radial clearance between the cap 30 and the neck 20.

[0076] More particularly, to prevent the projections 46 from interfering with the screwing stroke of the cap 30, the height “h” of the projections 46 is less than half of the nominal radial clearance “j0” between the external thread 32 and the internal thread 40 in the screwed position of the cap 30 on the neck 20. Preferably, there remains a residual radial clearance “j1” between the cap 30 and the projections 46, as shown in FIGS. 5 and 6.

[0077] When the neck 20 is equipped with a cover 42, the height “h” of a projection 46 is greater than the thickness of the radial tab 42A.

[0078] The presence of the projections 46 makes it possible to guarantee that there always remains a minimum radial clearance “j2” which is equal to the height “h” of a projection 46 between the cap 30 and the neck 20. This minimum radial clearance “j2” is greater than the thickness of the radial tab 42A of the cover 42.

[0079] Furthermore, to reduce the friction surface between the projections 46 and the thread 40 not comprising the projections 46, each projection 46 advantageously has a width, taken in the circumferential direction, which is very small, for example the width of each projection 46, taken in the circumferential direction, is less than its height “h” taken in the radial direction.

[0080] Each projection 46 is here in the form of a rib which axially connects two adjacent turns of the thread 32 which it equips. The rib thus extends in a radial axial plane.

[0081] Furthermore, each projection 46 has the same rigidity as the thread apex 40B against which it is intended to slide. The projection 46 more particularly is sufficiently rigid so as not to be substantially deformed during the screwing of the cap 30 onto the neck 20.

[0082] So that the projections 46 can distribute the nominal radial clearance “jO” around the neck 20 from the start of screwing the cap 30, at least one of the projections 46, preferably at least two, is arranged between the two upper end turns of the external thread 32. All the projections 46 are here arranged so as to be arranged opposite the thread crest 40B of the internal thread 40.

[0083] According to a first embodiment of the invention shown in Figures 4 and 5, the neck 20 has an external face 34 of cylindrical shape of revolution around the axis “A”. The external face 34 is here axially aligned over its entire axial length with the thread root 32A of the external thread 32.

[0084] Furthermore, the height “He” of the external thread 32 remains constant. Thus, the thread apex 32A of the external thread 32 extends over a cylinder of revolution centered on the main axis “A”.

[0085] As a result, the nominal radial clearance “jO” with the plug 30 is the same over the entire axial length of the neck 20. This nominal radial clearance “jO” is here 0.27 mm.

[0086] The radial tab 42A of the cover 42 here has a thickness of 80 μm. The height “h” of each projection 46 is here approximately 0.17 mm, or approximately twice the thickness of the radial tab 42A. This thus makes it possible to reserve the minimum radial clearance “j2” sufficient between the cap 30 and the neck 20 so that the radial tab 42A is received without radial clamping between the cap 30 and the neck 20.

[0087] Furthermore, there remains a residual radial clearance “jl” of 0.1 mm between the internal thread 40 and the projections 46 when the cap 30 occupies its screwed position on the neck 20.

[0088] According to a second embodiment of the invention shown in [Fig. 6], to increase the minimum radial clearance “j2” between the last turn of the internal thread 32 and the plug 30, the last turn 32s of the internal thread 32 has a height decreasing from bottom to top to a minimum height “He_min”, so that the nominal radial clearance “j0” between the thread crest 32B of the last turn 32s of the internal thread 32 and the thread root 40A of the last turn of the external thread 40 of the plug 30 is greater than the nominal radial clearance “j0” between the other turns of the internal thread 32 and the external thread 40.

[0089] For example, the nominal radial clearance “jO” between the top 32B of the thread of the last turn 32s of the internal thread 32 and the bottom 40A of the thread of the last turn of the external thread 40 of the plug 30 is 0.46 mm, while the nominal radial clearance “jO” between the other turns of the internal thread 32 and the external thread 40 is 0.27 mm.

[0090] To accentuate this nominal radial clearance “jO” as one approaches the free upper end of the neck, the non-threaded upper end portion 20A of the neck 20 has a truncated cone shape whose diameter reduces from bottom to top.

[0091] Thus, the nominal radial clearance “jO” between the external face 34 of the non-threaded portion and the thread crest 40B of the last turn of the internal thread 40 is for example equal to 0.37 mm instead of 0.27 mm as would be the case if the external face 34 of the neck 20 were entirely cylindrical.

Claims

Claims

1. Assembly (16) for closing a tube (10), said assembly (16) comprising: - a tube head (18) comprising a neck (20) extending along a main axis (A) to a free upper end edge (43), and comprising a helical external thread (32), the external thread (32) having a thread bottom (32A) and a thread top (32B), - a cap (30) comprising an internal thread (40) complementary to the external thread (32) to allow the cap (30) to be screwed onto the neck (20), the internal thread (40) having a thread bottom (40A) and a thread top (40B), characterized in that it comprises means for centering the cap relative to the neck (20) during its screwing formed by at least one projection (46) which extends from the bottom (32A) of thread of one of the external thread (32) or the internal thread and whose height (h) is less than that of said thread (32),a residual radial clearance (j 1 ) remaining between the cap (30) and the neck (20) at the level of the projections (46) in the screwed position of the cap (30) on the neck (20).,

2. Assembly (16) according to the preceding claim, characterized in that the external thread (32) or the internal thread comprises several projections (46) which are distributed regularly around the main axis (A).

3. Assembly (16) according to the preceding claim, characterized in that the projections (46) are four in number.

4. Assembly (16) according to any one of the preceding claims, characterized in that each projection (46) is arranged on the external thread (32) of the neck (20).

5. Assembly (16) according to any one of the preceding claims, characterized in that the cap and the neck are made of a rigid plastic material, such as HDPE.

6. An assembly (16) according to any preceding claim, characterized in that each projection (46) has the same rigidity as the thread crest (40B) of the other of the external thread or the internal thread (40).

7. Assembly (16) according to any one of the preceding claims, characterized in that each projection (46) is in the form of a rib which axially connects two adjacent turns of the thread (32).

8. An assembly (16) according to any preceding claim, characterized in that at least one of the projections (46) is arranged between the two upper end turns (32S) of the thread (32).

9. Assembly (16) according to any one of the preceding claims, characterized in that it comprises a cover (42) closing said neck (20), the cover (42) having a radial gripping tab (42A) folded against the external thread (32) of the neck (20), the radial tab (42A) being received in a nominal radial clearance (jO) between the upper end turn (40s) of the internal thread (40) and the neck (20).

10. Assembly (16) according to any one of the preceding claims, characterized in that the width of the projection, taken in the direction of the turn, is less than its height (h).

11. Assembly (16) according to any one of the preceding claims, characterized in that the upper end turn (32s) of the internal thread (32) has a height decreasing from bottom to top so that the nominal radial clearance (jO) between the thread crest (32B) of said end turn (32s) and the thread bottom (40A) of the external thread (40) of the plug 30 is greater than the nominal radial clearance (jO) between the other turns of the internal thread (32) and the external thread (40).

12. Assembly (16) according to any one of the preceding claims, characterized in that the neck (20) comprises a non-threaded upper end portion (20A), said portion (20A) having a frustoconical shape.

13. Tube (10) comprising a closure assembly (16) according to any one of the preceding claims.

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