EP1125638B1 - Pump comprising a movable part with a central duct and with a membrane hooked on the central duct, and container with the same - Google Patents

Abstract

A pump of the type comprising a moving member mounted to move relative to a support, the moving member having a central duct in which the substance to be dispensed penetrates via at least one opening, the support co-operating with the moving member to define a variable-volume pump chamber around said central duct, the pump having a diaphragm held by retaining means on the support, the diaphragm having a central portion in which one end of said central duct is inserted, the diaphragm having a valve-forming portion arranged to isolate the pump chamber from said opening(s) of the central duct while the volume of the pump chamber is increasing and the substance is being sucked into the pump chamber, the diaphragm also bearing against the moving member in such a manner that movement of the moving member to dispense the substance causes the diaphragm to be stretched elastically. The pump has means suitable, during movement of the moving member for dispensing the substance, for minimizing the stretching of the valve-forming portion of said diaphragm.

Description

The present invention relates to a pump and a container containing a liquid, for example a cosmetic or care cream, equipped with such a pump.

We know from French patent FR-B-2 728 809 a pump comprising a push button mounted to move on a support subject to the container containing the product to be dispensed, this push button comprising a central duct provided with a radial opening at its lower end, the support defining around this conduit central a variable volume pumping chamber. A membrane made in a elastomeric material is mounted on the support. This membrane has a part sleeve-shaped central unit open at its upper end and closed at its end lower. The central conduit of the push button is inserted into the membrane by a end until pressing against the bottom of the central part of the membrane.

The aforementioned membrane plays the function of a spring by bringing back the push button in its initial position after dispensing a dose of product.

It also performs the function of a discharge valve.

Indeed, during the return movement of the push button, the membrane is pressed onto the central duct and isolates the pumping chamber from the radial opening of the central duct to avoid re-entry of air into the pumping chamber.

Such a pump has the advantage of having only a small number of parts and therefore to be relatively inexpensive to manufacture.

However, this known pump is not entirely satisfactory.

In particular, the pump may be difficult to prime and in some cases the product circulates with difficulty between the central duct of the push button and the membrane, which can cause a blockage of the push button.

The invention aims to further improve a pump of the type comprising a movable member mounted to move relative to a support, this movable member comprising a central duct into which the product to be dispensed enters at the favor of at least one opening, the support defining with the movable member, around said central duct, a pumping chamber of variable volume, the pump comprising a membrane held by retaining means on the support, this membrane having a central part into which the central duct is inserted at one end, the membrane comprising a valve part, arranged so as to isolate the chamber pumping said opening (s) of the central duct when the volume of the pumping chamber increases and as product is sucked into it, the membrane further bearing on the movable member so that the displacement of the latter to dispense product produces an elastic stretch of the membrane.

The new pump according to the invention is characterized in that it comprises means suitable during movement of the movable member to distribute product to minimize stretching of the valve portion of the membrane. In an achievement preferred, the central part of the membrane comprises first attachment means arranged to cooperate with second attachment means integral with the duct central, these second attachment means being spaced from the end of the conduit by which the conduit is inserted in the central part of the membrane.

Thanks to the invention, the end of the central duct bears only weakly or not at all on the bottom of the central part of the membrane when the movable member is moved to dispense product, unlike the pump described in the patent French 2,728,809, in which the elastic stretching of the membrane is due to the fact that the central duct of the push button presses directly against the bottom of the part central sleeve-shaped membrane.

Advantageously, the portion of the membrane extending between the means of support retainer and the attachment zone on the central duct only exerts a spring function.

Advantageously also, the part of the membrane forming a valve, arranged to isolate the pumping chamber from the opening (s) of the central duct is located outside the portion of the membrane extending between the area of attachment to the support and the attachment area on the central duct.

In the invention, the central part of the membrane bears on the central duct at a location remote from the end of the latter, which allows reduce the mechanical stresses to which the bottom of the part is subjected membrane center.

In addition, because the bottom of the central part of the membrane is less mechanically stressed, it becomes easier to play the membrane its function of discharge valve, i.e. allowing it to isolate the pumping chamber from the or openings in the central duct when the volume of the pumping chamber increases and that product is sucked into it. The lower part of the central part of the membrane can deform more easily in a direction perpendicular to the direction of stretching of the upper part of the central part of the membrane, due to that it is subjected to less axial stresses, and the passage of the product to be distributed is thus facilitated.

In a particular embodiment, the first means of attachment of the membrane form an open groove in the opposite direction to the bottom of the part central of the membrane and the second attachment means comprise a skirt attachment directed towards the end of the central duct.

Still in a particular embodiment, the aforementioned groove is formed between two concentric tubular walls, respectively constituting the lower part and the upper part of the central part of the membrane, partially overlapping and joined by a transverse wall constituting the bottom of said groove.

Advantageously, the tubular wall forming the lower part of the part central of the membrane comprises, on its radially inner surface, at least one and preferably several axial channels.

These axial channels facilitate the flow of the product during the distribution of this one.

Advantageously, the above-mentioned axial channels extend downwards from the upper end of the tubular wall forming the lower part of the part center of the membrane, up to substantially below the above transverse wall.

Advantageously, the membrane is arranged to isolate the chamber from pumping of the opening (s) of the central duct by applying through a region annular, sealingly, on an area of the central duct located under the second attachment means.

This area of the central duct on which the membrane is applied when the volume of the pumping chamber increases and as product is drawn into this the latter is advantageously defined by an annular boss. The household membrane then with the central duct an annular clearance on either side of said boss, which facilitates the flow of the product during its distribution.

In a particular embodiment, the lower part of the central duct has at least one radial opening.

Alternatively, the lower part of the central duct has no radial opening, which facilitates its manufacture.

Advantageously, the second means for hooking the central duct are formed by the end of thicker parts of the central duct, these more thick, creating channels between them allowing the passage of the product towards the central duct openings.

Advantageously, the membrane comprises a flexible lip suitable, on the one hand for isolate the pumping chamber from the product source when the volume of the pumping decreases and, on the other hand, to allow a return of product in the pumping when the volume of the latter increases.

This flexible lip somehow plays the role of a suction valve.

In addition, the flexible lip is advantageously connected to the central part of the membrane by forming an annular groove open downwards and the retaining means are preferably formed by the end of an inner skirt coming to bear in the bottom of said groove, to retain the membrane when the movable member is moved towards the low to decrease the volume of the pumping chamber.

The aforementioned inner skirt advantageously has openings at its upper end, the height of which is less than that of the flexible lip, these openings allowing the product to reach the pumping chamber when the volume of the latter increases and the flexible lip moves away from the inner skirt under the effect of the push of the product flowing towards the pumping chamber.

The flexible lip is in a particular embodiment of increasing thickness in approaching the upper end of the membrane.

Still in a particular embodiment, the central part of the membrane is connected at its upper end to an annular part whose width and thickness are chosen so as to improve the maintenance of the membrane when the part center is stretched.

Advantageously, the support comprises a sealing means applying sealingly on a tubular skirt of the movable member, this tubular skirt being open downward and extending around the central duct concentrically with the latter, the tubular skirt further defining, radially outward, the pumping.

Advantageously, when the pump is at rest, the part of the membrane extending axially between the retaining means and the means for hooking the duct is tensioned, which keeps the movable member in high stop.

The invention also relates to a container equipped with a pump such as defined above.

• la figure 1 est une vue partielle et schématique, en coupe axiale, d'un récipient équipé d'une pompe conforme à un premier exemple de mise en oeuvre de l'invention,
• la figure 2 est une coupe axiale dans un plan perpendiculaire à celui de la figure 1,
• la figure 3 représente un détail de la figure 1,
• la figure 4 représente isolément le bouton-poussoir,
• la figure 5 représente un détail de la figure 4,
• la figure 6 représente isolément, en perspective et en coupe axiale, la membrane,
• la figure 7 est une coupe selon le trait VII-VII de la figure 4,
• la figure 8 est une vue analogue à la figure 1 représentant une première variante de réalisation de la pompe,
• la figure 9 est une coupe axiale dans un plan perpendiculaire à celui de la figure 8,
• la figure 10 représente un détail de la figure 8,
• la figure 11 représente isolément le bouton-poussoir de la pompe de la figure 8,
• la figure 12 représente un détail de la figure 11,
• la figure 13 est une vue analogue à la figure 1 représentant une deuxième variante de réalisation de la pompe,
• la figure 14 est une coupe axiale dans un plan perpendiculaire à celui de la figure 13,
• la figure 15 représente un détail de la figure 13, et
• la figure 16 représente isolément le bouton-poussoir de la pompe de la figure 13.

Other characteristics and advantages of the present invention will emerge on reading the detailed description which follows, of nonlimiting exemplary embodiments and on examining the appended drawing in which:

• FIG. 1 is a partial and schematic view, in axial section, of a container equipped with a pump according to a first example of implementation of the invention,
• FIG. 2 is an axial section in a plane perpendicular to that of FIG. 1,
• FIG. 3 represents a detail of FIG. 1,
• FIG. 4 represents the push button in isolation,
• FIG. 5 represents a detail of FIG. 4,
• FIG. 6 represents in isolation, in perspective and in axial section, the membrane,
• FIG. 7 is a section along the line VII-VII of FIG. 4,
• FIG. 8 is a view similar to FIG. 1 showing a first alternative embodiment of the pump,
• FIG. 9 is an axial section in a plane perpendicular to that of FIG. 8,
• FIG. 10 represents a detail of FIG. 8,
• FIG. 11 represents in isolation the push button of the pump of FIG. 8,
• FIG. 12 represents a detail of FIG. 11,
• FIG. 13 is a view similar to FIG. 1 showing a second variant embodiment of the pump,
• FIG. 14 is an axial section in a plane perpendicular to that of FIG. 13,
• FIG. 15 represents a detail of FIG. 13, and
• FIG. 16 represents the push-button of the pump of FIG. 13 in isolation.

Partly shown in FIG. 1 is a container 1 comprising a body 2 forming a reservoir, of which only the upper end is seen in the drawing defining a neck 3 on which a support 4 is snapped on.

This support 4 constitutes a guide for mounting sliding along an axis X of a push button 5 and is also used for mounting a closing cover removable 6, covering the push button 5 before the first use.

In the embodiment described, the support 4 includes a skirt seal 7 applying in a sealed manner on the inner surface of the neck 3.

The sealing skirt 7 is extended radially, on the one hand towards the outside by fixing lugs 8 snapped onto an annular bead 9 of the neck 3 and other goes inward by a stepped wall 10 defining a nozzle 12 used for connection of a dip tube, not shown.

An outer skirt 15 and a guide skirt 16 are made in one holding by plastic molding with the sealing skirt 7, the fixing lugs 8 and the stepped wall 10.

The outer skirt 15 extends around the neck 3 of the container and has a shoulder 17 on which the closure cover 6 bears.

The upper edge 18 of the outer skirt 15 retains the push button 5 at rest, as will be explained below.

The support 4 comprises an inner skirt 20 constituted by a part insert or insert, having a lower end 21 forcibly engaged in the stepped wall 10.

The inner skirt 20 has a substantially tapered upper end, provided with radial openings 22, as can be seen more particularly on the figure 3.

These openings 22 are in the example described in the form of slots oriented along the X axis, extended downward by grooves 25 extending over the radially inner surface of the inner skirt 20 until a step 26.

A double annular sealing lip 24 is produced in one piece with the inner skirt 20 on the outer side of the latter by plastic molding.

The push button 5 has an outer skirt 30, provided with its lower end of teeth 31 abutting against the upper edge 18 of the skirt outside 15 of the support 4 when the push button 5 is at rest in the high position, as shown in figure 1.

The push button 5 also includes a central duct 32, of axis X, and a tubular skirt 33 concentric, defining around the central duct 32 a chamber 34 annular pumping.

The outer skirt 30, the tubular skirt 33 and the central duct 32 are made in one piece by plastic molding with a dispensing nozzle 35, communicating internally with the central duct 32.

The latter comprises, at its lower end 87, in the example of embodiment of FIGS. 1 to 3, radial openings 36.

The lower end of the tubular skirt 33 forms a sealing lip 37, extending slightly radially outward.

The guide skirt 16 of the support 4 has in the upper part a surface inner 40 cylindrical of revolution and in the lower part a slight annular withdrawal 41.

When the push button 5 is in the high position, the sealing lip 37 applies tightly to the inner surface 40 of the upper part of the guide skirt 16, as shown in FIG. 1.

The interior of the container is thus isolated from the ambient air, which is favorable to good conservation of the product.

When the push button 5 is pressed, the sealing lip 37 ceases to apply tightly to the guide skirt 16, due to the existence of the shrinkage annular 41, which allows the annular groove formed between the inner skirts 20 and guide 16 to communicate with the outside through the annular clearance 42, shown in the figure 3.

The inner skirt 20 is used for mounting a membrane 50, shown in isolation in FIG. 6, having a central part 51 in the form of a sleeve, of axis X, open at its upper end and closed at its lower end by a bottom 52.

The membrane 50 is made of a nitrile or silicone elastomer and comprises in the upper part a flexible annular lip 53 directed downwards.

This flexible lip 53 forms, by connecting with the central part 51, a annular groove 54 open downwards, into which the inner skirt 20 is inserted at its upper end, up to rest on its free edge in the bottom of this groove 54 against the wall 55 connecting the flexible lip 53 to the central part 51.

The flexible lip 53 is made so as to slightly tighten the skirt interior 20 at rest.

The height of the flexible lip 53 is greater than that of the openings 22 and the flexible lip 53 is able to be applied, at rest, in a sealed manner against the surface outside of the inner skirt 20, below the openings 22, as illustrated in the figure 1.

The flexible lip 53 acts as a suction valve, isolating the chamber pumping 34 from inside the container when the volume of the pumping chamber decreases to distribute a dose of product, as will be explained below.

The wall 55 which joins the flexible lip 53 to the central part 51 is relatively wide and thick, which makes it possible to immobilize the upper end of the central part 51 of the membrane relative to the inner skirt 20, when the push button 5 is pressed.

The central duct 32 has on its outer surface parts more thick 60 extending axially, three in number in the embodiment described, separated by axial channels 61 as can be seen in FIG. 7.

Channels 61 extend over most of the height of the conduit central 32 from its upper end over the entire length of the thicker parts 60.

The latter form at their lower end a hanging skirt 64 which houses with the central duct 32 an annular groove 65 open downwards.

In the embodiment described, the hanging skirt 64 is located between a quarter and a third of the total height of the central duct 32 from its end lower 87.

The central part 51 of the membrane 50 has an upper part 56 and a lower part 57.

The latter is connected to the upper part 56 by a transverse wall. 58 extending radially inward from the lower end of the portion upper 56.

The lower part 57 extends above the transverse wall 58 to the inside of the upper part 56 to form a hanging skirt 59, forming with the upper part 56 an annular groove 70 open upwards.

When the membrane 50 is in place on the support 4, the hanging skirt 64 of the central duct 32 is housed in the groove 70 and the attachment skirt 59 of the membrane 50 is housed in the groove 65, so that when the push button 5 is pressed in, the central part 51 of the membrane is pulled down essentially thanks to the attachment of the membrane to the attachment skirt 64 of the central duct 32.

The thickness of the hanging skirt 64 corresponds substantially to the width of the annular groove 70.

Axial channels 72 are produced on the inner face of the lower part 57 of the central part 51 of the membrane, as can be seen in FIG. 6.

These channels 72 have a depth which decreases gradually as and as we get closer to the bottom 52 of the membrane, as we can see on Figure 3.

In the embodiment described, the channels 72 open at the end upper part of the lower part 57 of the membrane.

The annular region 75 of the lower part 57 of the membrane, which extends axially between the lower end of the channels 72 and the bottom 52, has a height greater than that of the radial openings 36 of the central duct 32.

In addition, in the example of embodiment described, the internal diameter of this annular region 75 is chosen so that at rest it applies so watertight on the central duct 32 above the radial openings 36 and thus insulates these last of channels 72.

The operation of pump 1 is as follows.

It is assumed that pump 1 is primed.

When the user presses the push button 5, the central duct 32 moves down and the upper part 56 of the membrane, retained at its part upper by the upper end of the inner skirt 20 and engaged at its end lower on the hanging skirt 64, elastically stretches.

The product contained in the pumping chamber 34 is compressed and the lip flexible 53 is applied in leaktight manner to the outer face of the inner skirt 20.

Under the pressure of the product, the annular region 75 of the membrane 50 deviates of the central duct 32 and the product can reach the radial openings 36 to flow through the interior of the central duct to the outlet orifice of the dispensing nozzle 35.

Thanks to the attachment of the membrane 50 to the central duct 32 in one location far from the bottom 52, the latter is only slightly mechanically stressed during the distribution of the product and the annular region 75 which is not stretched further measurement can deviate relatively easily from the central duct 32 under the pressure of the product flowing through channels 61.

When the user releases the push button 5, the upper part 56 of the membrane 50 returns, thanks to its elasticity, to its initial shape and brings back the push button 5 up.

A vacuum is then created in the pumping chamber 34, which has for effect of detaching the flexible lip 53 from the inner skirt 20 and allows the product to gain the pumping chamber 34 by circulating through the inside of the nozzle 12 and the grooves 25 made on the inner face of the inner skirt 20.

The depression which is created in the pumping chamber 34 during the raising the push button 5 also has the effect of pressing the annular region 75 of the membrane against the central duct 32 and therefore of isolating the radial openings 36 from the pumping chamber 34.

In the pump according to the invention, the spring function of the diaphragm is in somehow independent of the discharge valve function, thanks to the hooking of the membrane on the central duct at a location remote from the end membrane.

In other words, between the two attachment regions of the membrane on the support and on the central duct respectively, the membrane has no other function only a spring function and does not exercise a valve function.

To assemble pump 1, we start by installing the membrane 50 on the central duct 32 of the push button 5 then the latter is put in place on the support 4, the teeth 31 crossing by elastic deformation the upper edge 18 of the outer skirt 15.

The length of the upper part 56 of the membrane 50 is chosen such that so that when the push button 5 comes to bear by the teeth 31 against the edge upper 18 above, the membrane is stretched.

FIGS. 8 to 12 show a first alternative embodiment.

In these figures, the same reference signs will be used for elements identical to those which have just been described.

The pump 1 'shown in Figures 8 to 12 differs from that which has been previously described by the shape of the central duct 32 'of the push button 5' and that of the membrane 50 '.

More specifically, the central duct 32 ′ comprises in this variant of realization of a radial opening 36 'of reduced height and, at a relatively distance weak of its lower end 87 and above the radial opening 36 ', a boss ring finger 80.

The central duct 32 'is for the rest identical to the central duct 32 previously described.

The membrane 50 'has a central part 51', the lower part 57 'of which has an inside diameter slightly larger than that of the lower part 81 of the central duct 32 ′, and cleaning therewith an annular clearance 82, as can be seen see in figure 10.

The inner diameter of the lower part 57 'corresponds to the diameter outside of the annular boss 80, so that the lower part 57 ′ is applied at rest sealingly on this annular boss 80.

Axial channels 72 ′ are produced on the inner face of the part lower 57 '.

These channels 72 'open at their lower end into the annular clearance 82 above boss 80.

The membrane 50 'is identical for the rest to the membrane 50 previously described.

In the embodiment of Figures 8 to 12, the flow of the product during the push-button 5 'is easier to push, thanks to the presence of the annular clearance 82.

FIGS. 13 to 16 show a 1 "pump conforming to a second variant embodiment of the invention.

This 1 "pump differs from the pump shown in FIG. 1 in that the central duct 32 "of the push button 5" does not have radial openings 36 but simply the axial opening 86 defined by the circular edge of the end bottom 87 of the central duct 32 ".

Despite this, the 1 "pump can still function properly due to the fact that the bottom 52 of the membrane 50, the thickness of which is substantially the same as that of the annular region 75, can deform downwards under the effect of product pressure during of the push-button 5 "being pushed in, the bottom 52 not being tensioned by the fact that the membrane 50 is hung higher on the hanging skirt 64.

Of course, the invention is not limited to the exemplary embodiments which have just been described.

One can in particular modify the shape of the membrane, that of the means for attaching the membrane to the central duct, as well as the shape of the support and the push button, without departing from the scope of the present invention.

Claims (24)

1. A pump (1; 1'; 1") of the type comprising a moving member (5; 5'; 5") mounted to move relative to a support (4), the moving member having a central duct (32; 32'; 32") in which the substance to be dispensed penetrates via at least one opening (36; 36'; 86), the support (4) co-operating with the moving member to define a variable-volume pump chamber (34) around said central duct, the pump having a diaphragm (50;.50') held by retaining means (20) on the support (4), the diaphragm having a central portion (51; 51') in which one end (87) of said central duct is inserted, the diaphragm having a valve-forming portion arranged to isolate the pump chamber (34) from said opening(s) (36; 36'; 86) of the central duct while the volume of the pump chamber is increasing and the substance is being sucked into the pump chamber, the diaphragm also bearing against the moving member in such a manner that movement of the moving member to dispense the substance causes the diaphragm to be stretched elastically, the pump being characterized by the fact that it has means suitable, during movement of the moving member for dispensing the substance, for minimizing the stretching of the valve-forming portion of said diaphragm.
2. A pump according to claim 1, characterized by the fact that the diaphragm (50; 50') has first engagement means (59) arranged to co-operate with second engagement means (64) secured to said central duct, said second engagement means being spaced apart from the end (87) of the central duct.
3. A pump according to claim 1 or 2, characterized by the fact that the portion of the diaphragm extending between the retaining means (20) of the support and the engagement zone of the central duct performs a spring function only.
4. A pump according to the preceding claim, characterized by the fact that the portion of the valve-forming diaphragm that is arranged to isolate the pump chamber from the opening(s) of the central duct lies outside the portion of the diaphragm that extends between the zone for fixing on the support and the zone for engagement on the central duct.
5. A pump according to any preceding claim, characterized by the fact that the first engagement means (59) of the diaphragm form a channel (70) that is open in the direction facing away from the end wall (52) of the central portion of the diaphragm, and the second engagement means comprise an engagement skirt (64) directed towards the end (87) of the central duct.
6. A pump according to the preceding claim, characterized by the fact that the channel (70) is formed between two concentric tubular walls (56, 57) respectively constituting the bottom portion and the top portion of the central portion of the diaphragm, that overlap in part, and that are united by a transverse wall (58) constituting the web of said channel (70).
7. A pump according to the preceding claim, characterized by the fact that the tubular wall (57; 57') forming the bottom portion of the central portion of the diaphragm has at least one and preferably a plurality of axial slots (72; 72') in its radially inner surface.
8. A pump according to the preceding claim, characterized by the fact that said axial slots (72; 72') extend downwards from the top end of the tubular wall (57; 57') forming the bottom portion of the central portion of the diaphragm to perceptibly beneath the transverse wall (58).
9. A pump according to any preceding claim, characterized by the fact that the diaphragm is arranged to isolate the pump chamber from the opening(s) (36; 36'; 86) of the central duct by causing an annular region (75) to bear in leakproof manner against a zone of the central duct situated beneath the second engagement means.
10. A pump according to the preceding claim, characterized by the fact that the zone of the central duct against which the diaphragm bears while the volume of the pump chamber is increasing and the substance is being sucked into the pump chamber is defined by an annular bead (80).
11. A pump according to the preceding claim, characterized by the fact that the diaphragm co-operates with the central duct to provide annular clearance (82) on either side of said bead (80).
12. A pump according to any preceding claim, characterized by the fact that the bottom portion of the central duct has at least one radial opening (36; 36').
13. A pump according to any one of claims 1 to 10, characterized by the fact that the bottom portion of the central duct does not have any radial opening.
14. A pump according to any preceding claim, characterized by the fact that the second engagement means of the central duct are constituted by the ends of thicker portions (60) of the central duct, said thicker portions leaving slots (61) between one another enabling the substance to pass towards the opening(s) of the central duct.
15. A pump according to any preceding claim, characterized by the fact that the diaphragm has a flexible lip (53) suitable firstly for isolating the pump chamber from the source of substance while the volume of the pump chamber is decreasing, and secondly for enabling the substance to penetrate into the pump chamber while the volume thereof is increasing.
16. A pump according to the preceding claim, characterized by the fact that the flexible lip (53) is connected to the central portion of the diaphragm so as to form a downwardly open annular channel, and by the fact that the retaining means are constituted by the end of an inner skirt (20) coming to bear against the web of said channel so as to retain the diaphragm when the moving member is moved downwards in order to decrease the volume of the pump chamber.
17. A pump according to the preceding claim, characterized by the fact that the inner skirt (20) has openings (22) at its top end, the height of the openings being less than the height of the flexible lip (53), said openings enabling the substance to reach the pump chamber while its volume is increasing, and while the flexible lip is spaced apart from the inner skirt under the effect of thrust from the substance flowing towards the pump chamber.
18. A pump according to any one of the three preceding claims, characterized by the fact that the flexible lip (53) is of thickness that increases going towards the top end of the diaphragm.
19. A pump according to any one of the four preceding claims, characterized by the fact that the central portion of the diaphragm is connected at its top end to an annular portion (55) of width and thickness selected in such a manner as to improve retention of the diaphragm while said central portion is being stretched.
20. A pump according to any preceding claim, characterized by the fact that the support (4) includes sealing means (24) bearing in leakproof manner against the tubular skirt (33) of the moving member, said tubular skirt being downwardly open and extending concentrically around the central duct (32; 32'; 32"), said tubular skirt (33) also defining the radially outer wall of the pump chamber.
21. A pump according to any preceding claim, characterized by the fact that when the pump is at rest, the portion (56) of the diaphragm that extends axially between the retaining means and the engagement means of the duct is under tension.
22. A pump according to any preceding claim, characterized by the fact that the moving member constitutes the pushbutton (5; 5'; 5"), the central duct being integrally formed with a dispensing endpiece (35).
23. A pump according to any preceding claim, characterized by the fact that the diaphragm (50; 50') is made of a nitrile elastomer or a silicon elastomer.
24. A receptacle fitted with a pump as defined in any preceding claim.

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