EP1050480B1 - Diaphragm pump comprising a preferential deformation area on at least a part of its periphery, and container incorporating the same - Google Patents

Abstract

Pump comprises membrane having central part (51) in shape of sleeve open at its upper end and closed at its lower end. Centr conduit is inserted in sleeve. Membrane is arranged so as to isolate openings of pumping chamber when volume of chamber increase and product is induced into it. Lower part of central part of membrane has preferential deformation zone over sector (77) of its periphery. An Independent claim is also included for the dispenser.

Description

The present invention relates to a pump according to the preamble of claim 1 and a container containing a liquid, for example a cosmetic cream, equipped with such a pump.

We know from French patent FR-A-2,728,809 a pump comprising a push button mounted on the move on a support subject to the container containing the product to be dispensed, the push button comprising a cylindrical central duct of revolution, provided with radial openings at its lower end, the support defining around this duct an annular pumping chamber, of volume variable. A membrane made of an elastomer is mounted on the support. This membrane has a symmetrical central part of revolution, in the form of a sleeve open at its upper end and closed at its lower end. The central duct of the push button is inserted into the membrane until it presses against the bottom of the muff.

The membrane thus constitutes an elastic return member making it possible to return the push button to its initial position after dispensing a dose of product.

In addition, during the return movement of the push button, the membrane in tacking on the central duct isolates the pumping chamber and avoids a re-entry of air into it.

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 does not offer complete satisfaction, the company Applicant having observed a tendency for the push button to lock up and / or poor reconstitution and dose distribution.

In addition, such a pump presents priming difficulties.

The present invention aims to improve the reliability of the operation of a pump of the type defined above, namely comprising a movable member mounted at displacement relative to a support, the movable member comprising a central duct in which the product to be distributed enters through at least one opening, the support defining with the movable member, around said central duct, a pumping chamber of variable volume, this pump further comprising a membrane having a central part in the form of a sleeve open at its end upper and closed at its lower end, central part in which is inserted said central duct, the membrane being arranged so as to isolate said one or more pumping chamber openings when the volume of the pumping chamber increases and product is drawn into it, the pumping chamber being isolated from the product source when the volume of said chamber pumping decreases.

It achieves this by the fact that the lower part of the central part of the membrane has a deformation zone on at least one sector of its periphery preferential, advantageously constituted by a thinned zone.

Thanks to this or these preferential deformation zones, it is possible to make a pump in which the central part of the membrane exerts a force of relatively large reminder on the movable member to return it to its position rest, without preventing the product contained in the pumping chamber from reach the central duct to be distributed when the user presses on the organ mobile.

In a particular embodiment, the lower part of the central part of the membrane has at least two diametrically opposite thinned zones.

Still in a particular embodiment, each thinned zone is formed by a reduction in the thickness of the membrane of at least 20%, preferably at least 25%.

Advantageously, the inner surface of the central part of the membrane exhibits an inward recess.

This recess is preferably located at the upper end of the or the aforementioned preferential deformation zones.

In a particular embodiment, the membrane includes a flexible lip capable, on the one hand to isolate the pumping chamber from a source of product when the volume of said pumping chamber decreases, and on the other hand, to allow a return of product in said pumping chamber when the volume of the latter increases.

In a particular embodiment, this flexible lip is connected to the part central part of the membrane by forming an annular groove open downwards, and the support includes an inner skirt bearing at its upper end in the bottom of said groove to retain the membrane when the movable member is moved towards the bottom to decrease the volume of the pumping chamber.

Preferably, the aforementioned inner skirt has openings at its upper end whose height is less than that of the flexible lip, these openings allowing product to be drawn into the pumping chamber when the volume of the latter increases and the flexible lip deviates from the inner skirt.

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

Preferably, the thickness of the abovementioned annular part, before mounting the membrane in the pump, is greater than or equal to the thickness of the membrane in its central part.

Preferably, the aforementioned annular part is, before mounting the membrane in the pump, at least 1.5 times wider than thick, and preferably 2 times wider is thick.

Advantageously, the bottom of the central part has, before mounting the membrane in the pump, roughly the same thickness as the side wall of the central part of the membrane outside of said deformation zone (s) preferred.

Preferably, the thickness of the bottom corresponds to 20% near the thickness of the side wall of the central part of the membrane, outside of the said zone or zones preferential deformation, before mounting the diaphragm in the pump.

In a particular embodiment, the height of the aforementioned flexible lip is greater than or equal to the height of the central part of the membrane, before mounting of the latter in the pump.

In a particular embodiment, the flexible lip is of increasing thickness while closer to the upper end of the membrane.

In a particular embodiment, the outer surface of said flexible lip has, from its lower end, a cylindrical lower portion of revolution around the axis of the central part of the membrane, then a portion diverging conical upper in approach to the upper end of the membrane, this last conical portion connecting by a shoulder to a annular rib.

Preferably, the inside diameter of the flexible lip is equal to the tolerances manufacturing close to the outside diameter of the inner skirt.

More preferably, the clearance between the flexible lip and the inner skirt is negative or zero; thus, the flexible lip is tightened slightly on the inner skirt.

In a particular embodiment, when the movable member is at rest, the length of the central part of the diaphragm, after mounting in the pump, is greater than or equal to 1.5 times its initial length before mounting in the pump and preferably greater than or equal to 2 times said initial length, and more preferably, greater than or equal to 3 times said initial length.

In a particular embodiment, when the movable member is completely pressed, the length of the central part of the membrane is greater than or equal to 2 times the initial length of the membrane before mounting on the pump, preferably greater than or equal to 3 times said initial length and preferably still greater or equal to 4 times said initial length.

In a particular embodiment, at least one of the membrane and the conduit central is shaped to prevent the formation between the membrane and the central duct, a sealed annular zone preventing the product contained in the pumping to flow through the central duct when the volume of the chamber pumping decreases.

Preferably at least one of the membrane and the central duct is shaped to bear against the other of the membrane and the central duct in predetermined locations of its periphery, at least during the relative displacement of the movable member and of the support.

Preferably, at least one of the membrane and of the central duct comprises reliefs against which the other of the membrane and the central duct comes to bear, at less during the relative movement of the movable member and the support.

This guarantees reliable operation of the pump, without risk of blockage. of the movable member when the volume of the pumping chamber varies.

The aforementioned reliefs tend in fact to prevent any blockage by the membrane of the circulation of the product coming from the pumping chamber towards the opening (s) the central conduit through which the product to be distributed enters, when the volume of the pumping chamber decreases.

These reliefs also tend to maintain the central duct of the movable member in the axis of the central part of the membrane, which is favorable for a satisfactory pump operation.

In a preferred embodiment, said reliefs are produced on the membrane in preferably being formed by equi-distributed bosses around the axis of the part central part of the membrane at its opening, these bosses extending from preferably on the upper side of the membrane.

In a particular embodiment, the support has a double lip sealing, applying sealingly on a tubular skirt of the movable member, this tubular skirt being open downward and extending around the central duct concentrically to the latter, this tubular skirt further delimiting radially towards outside the pumping chamber.

In a particular embodiment, the inner skirt of the support is part of a patch on the rest of the support.

In a preferred embodiment, the central duct of the movable member is provided, at its lower end, at least one radial opening.

In a preferred embodiment, the movable member constitutes a push button, the the aforementioned central duct being produced in one piece with a dispensing nozzle.

In a particular embodiment, the tubular skirt of the movable member slides at the interior of a support guide skirt, forming with the interior skirt of the supports an annular groove open upwards, communicating through at least one orifice air intake with the product source, the tubular skirt of the movable member applying sealingly to said guide skirt when the movable member is at rest and the volume of the pumping chamber is maximum.

The membrane can be made of a nitrile elastomer or an elastomer silicone.

In a particular embodiment, the pump includes a return spring for recall the movable organ to an initial position after dispensing a dose of product.

This return spring is advantageously constituted by a helical spring working in compression.

This spring is preferably arranged in the axis of the membrane, so as to apply by its upper end to the lower end of the central part of the membrane.

The presence of a return spring is advantageous because it facilitates the choice of the material which may constitute the membrane, since the latter may then not be prestress or undergo a relatively weak prestress.

It also widens the range of products that can be distributed, since becomes easier to find, to make the membrane, a material compatible with the product to distribute.

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

• la figure 1 est une vue schématique de la partie supérieure d'un récipient équipé d'une pompe conforme à l'invention,
• les figures 2 et 3 représentent isolément la jupe intérieure du support,
• la figure 4 représente isolément et partiellement, l'extrémité inférieure de la jupe tubulaire de l'organe mobile,
• la figure 5 représente isolément, en coupe axiale schématique, la membrane destinée à équiper la pompe de la figure 1, avant son montage dans la pompe,
• la figure 6 est une coupe selon le trait de coupe VI-VI de la figure 5,
• la figure 7 est une coupe selon le trait de coupe VII-VII de la figure 5,
• la figure 8 est une vue de dessous de la partie centrale de la membrane, selon la flèche VIII de la figure 5,
• la figure 9 illustre le fonctionnement de la pompe lorsque l'on appuie sur le bouton-poussoir,
• la figure 10 illustre le fonctionnement de la pompe lorsque l'on relâche le bouton-poussoir,
• la figure 11 représente de façon partielle et schématique le conduit central d'un bouton-poussoir conforme à une variante de mise en oeuvre de l'invention, et
• la figure 12 est une section transversale selon le trait de coupe X"-X" de la figure 10.

Other characteristics and advantages of the present invention will appear on reading the detailed description which follows, of a non-limiting exemplary embodiment of the invention and of an alternative embodiment, and on examining the attached drawing, in which:

• FIG. 1 is a schematic view of the upper part of a container fitted with a pump according to the invention,
• FIGS. 2 and 3 represent the inner skirt of the support in isolation,
• FIG. 4 represents, in isolation and partially, the lower end of the tubular skirt of the movable member,
• FIG. 5 represents in isolation, in schematic axial section, the membrane intended to equip the pump of FIG. 1, before its mounting in the pump,
• FIG. 6 is a section along the section line VI-VI of FIG. 5,
• FIG. 7 is a section along the section line VII-VII in FIG. 5,
• FIG. 8 is a bottom view of the central part of the membrane, according to arrow VIII in FIG. 5,
• FIG. 9 illustrates the operation of the pump when the push button is pressed,
• FIG. 10 illustrates the operation of the pump when the push button is released,
• FIG. 11 partially and schematically represents the central duct of a push button in accordance with an alternative embodiment of the invention, and
• FIG. 12 is a cross section along the section line X "-X" in FIG. 10.

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

The support 4 guides in sliding, along an axis X, a push button 5 and serves mounting a removable protective cover 6, covering the push button 5 before the first use.

The support 4 includes a sealing skirt 7 which is applied in a sealed manner on the inside 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 on the other hand inward by a stepped wall 10 defining a nozzle 12 used for connection of a dip tube 13, partially shown in the drawing.

An outer skirt 15 and a guide skirt 16 are made in one piece 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 protective cover 6 is supported.

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

The support 4 includes an inner skirt 20 constituted by an attached piece, having a stepped lower end 21, forcibly engaged in the stepped wall 10.

The inner skirt 20 has a substantially tapered upper end, provided with openings 22, as can be seen more particularly in Figures 2 and 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 by plastic molding.

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

The push button 5 comprises a central duct 32, of axis X, and a skirt tubular 33 concentric, delimiting around the central duct 32 a 34 annular pumping.

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

The latter has, at its lower end, radial openings 36.

The lower end of the tubular skirt 33 forms a sealing lip 37, extending slightly radially outward, as shown more particularly in Figure 4.

The guide skirt 16 of the support 4 has a slight shrinkage in the lower part annular 41 on its radially inner surface.

When the push button 5 is in the high position, the sealing lip 37 applies tightly to the cylindrical surface of revolution 40 of the part 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 for a 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 groove formed between the inner and guide skirts 20 16 to communicate with the outside.

An air intake orifice 42 is made in the bottom of this groove to allow air to re-enter the container as it is emptied.

The inner skirt 20 is used for mounting a membrane 50 having a part sleeve-shaped central unit 51, of axis X, open at its upper end and closed at its lower end by a bottom 52.

This central part 51 is extended radially outwards by a lip flexible annular 53, as can be seen more particularly in FIGS. 5 and 6.

This flexible lip 53 forms, by connecting with the central part 51, a annular groove 54 into which the inner skirt 20 is inserted at its end upper, until taking support by its free edge in the bottom of said groove.

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

The height of the flexible lip 53 is greater than that of the openings 22 and the flexible lip 53 is suitable for applying at rest in a sealed manner by its surface inner 56 against the radially outer surface of the inner skirt 20 below openings 22, as shown in Figure 1.

The flexible lip 53 can deform radially outward to allow to the product to gain the pumping chamber 34, as will be explained below.

The membrane 50 comprises, at the opening of its central part 51, non-symmetrical reliefs of revolution around the X axis, namely in the example in particular bosses 55 whose function will be specified below.

In the embodiment described, these bosses 55 are three in number, being evenly distributed angularly around the X axis, as can be seen in the figure 6.

Each of these bosses 55 protrudes from the radially inner surface of the central part 51 along approximately half (before its mounting in the pump) of the height thereof from its upper end and extends radially outwards on the upper face of the membrane 50 up to substantially above of the groove 54, as can be seen in FIG. 5.

Each of the bosses 55 further presents, when observed in section in a transverse section plane, a convex section towards the X axis, as shown in the figure 6.

The inner surface of the central part 51 of the membrane has a upper portion 70 slightly conical towards the bottom 52.

The bosses 55 are produced on this conical portion 70, as can be see in figure 5.

The conical surface 70 is connected by a recess 71 directed inwards to a cylindrical surface 72 of revolution around the axis X.

The outer surface of the central part 51 of the membrane has a conical portion 73 parallel to the conical upper portion 70, which is connected by a step 74 parallel to step 71, to a surface 75 formed by a alternating sectors 76 and 77 cylindrical of revolution around the X axis, presenting different diameters.

More particularly, as can be seen in FIG. 7, the sectors 77, at number of two, extend over 90 ° each, are diametrically opposed, and have a diameter smaller than sectors 76.

The sectors 77 define with the cylindrical interior surface 72 two zones diametrically opposite thinned 78s, the function of which will be specified below.

The sectors 76 are joined by a band 79 extending on the underside of the bottom 52 and whose sides 80 are parallel, as can be seen in FIG. 8.

The inner surface 56 of the flexible lip 53 is conical, converging towards the top, as can be seen in Figure 5.

The outer surface of the flexible lip 53 has, from its end lower, a lower portion 81 substantially cylindrical of revolution around the X axis, then a conical upper portion 82 diverging upward, this portion conical 82 connecting by a shoulder 83 to an annular rib 84.

As can be seen in FIG. 5, the annular part 85 which joins the lip flexible 53 at the central part 51 is relatively wide and thick, which allows good immobilize the upper end of the central part 51 relative to the skirt interior 20 when the central part 51 is stretched.

In the example of embodiment described, the annular part 85 is approximately 2 times more wide than thick, apart from the bosses 55.

The thickness e ₁ of the bottom 52 is in the example described substantially the same as the thickness e ₂ of the side wall of the central part 51 between the surfaces 73 and 70, outside the bosses 55.

The thickness e ₃ of the central part 51 measured between the surfaces 72 and 77 is approximately 0.75 times the thickness e ₂ , in the embodiment described.

By way of example, in the example of embodiment described, the thickness e ₁ is equal to 0.55 mm, the thickness e ₂ is equal to 0.55 mm and the thickness e ₃ is equal to 0.4 mm (thicknesses measured before mounting the diaphragm in the pump).

When the push button 5 is at rest, as shown in FIG. 1, the length of the central part 51 of the membrane is approximately 3 times the initial length l ₀ of the central part 51, that is to say that l elongation reaches 200%.

By way of example, when the membrane 50 is not mounted, the length lo measured between the bottom of the groove 54 and the upper face of the bottom 52 is approximately 3 mm and when the membrane is in place in the pump and the push button at rest as shown in Figure 1, the length of the central part 51 is 9 mm about.

In the example described, at the end of the depressing stroke of the push button 5, the length of the central part 51 reaches an elongation of 350%.

The length of the central part 51 is then, for the example considered, 13.5 mm, the stroke of the push button 5 down being 4.5 mm.

During assembly, the central conduit 32 of the push button 5 is inserted into the central part 51 of the membrane 50 until it bears, by its end lower, against the bottom 52 of the membrane 50, as illustrated in FIG. 1.

The bosses 55 then apply, in the example described, against the surface cylindrical of revolution of the central duct 32. However, it is not necessary to in general, that the bosses 55 are applied to the central duct 32 when the push button is at rest.

When the push button 5 is at rest, the central part 51 of the membrane 50 is stretched so as to keep the teeth 31 in abutment against the upper edge 18 of the outer skirt 15.

The double sealing lip 24 is applied tightly to the surface radially inner of the tubular skirt 33, whatever the upward movement or down from push button 5.

The radially inner surface of the central part 51 of the firm membrane the radial openings 36 of the central duct 32.

The flexible lip comes to rest by its internal surface 56 on the skirt interior 20.

The support 4, the push button 5 and the membrane 50 constitute a pump whose operation is as follows.

When the user presses the push button 5, as illustrated in the FIG. 9, the central duct 32 drives down the bottom 52 of the membrane 50, which deforms elastically by stretching to accompany the movement of descent of the central duct 32.

The pump is here assumed to be primed, that is to say that the pumping chamber 34 is filled with product.

During the downward movement of the push button 5, the product contained in the pumping chamber 34 is driven between the central duct 32 and the part central 51 of the membrane and gains the radial openings 36 of the central duct 32, then the dispensing nozzle 35.

The flexible lip 53 is applied in a sealed manner by its internal surface 56 on the inner skirt 20 during the downward movement of the push button 5.

The sealing lip 37 of the tubular skirt 33 of the push button 5 ceases, when it reaches the annular withdrawal 41 after a certain driving stroke of the push button 5, to apply in a sealed manner on the guide skirt 16, allowing communication between the inside of the container and the outside, by through the air intake orifice 42 and the clearance existing between the guide skirt 16 and the tubular skirt 33.

The bosses 55 between them provide passages for the product and prevent the formation of a sealed annular zone between the central duct 32 and the central part 51 of the membrane 50 which could not be overcome by the pressure of the product, so that the product can flow to the radial openings 36, the membrane 50 being able deviate slightly from the central duct 32 in the vicinity of the upper end of the openings 36 under the effect of product pressure.

The existence of the thinned zones 78 favors the outward deformation of the side wall of the central part 51 to allow the product to enter the radial openings 36.

The existence of the recess 71 allows the product to descend more easily along the central duct 32 to the radial openings 36, without risk of blockage of the circulation of the product through the membrane 50.

The bosses 55 tend to keep the central duct 32 coaxial with the skirt inner 20 and to guarantee the attachment of the membrane to the inner skirt 20.

When the user releases the push button 5, it is called back to the high by the central part 51 of the membrane which tends to return to its initial shape.

Thanks to the presence of the thinned zones 78, the central part 51 can have apart from the latter a relatively large thickness of material which allows to sufficiently stretch the central part 51 during the positioning of the membrane 50 in the pump to obtain the restoring force making it possible to return safely blocking the push button 5 upwards.

During the return movement of the push button 5, the central part 51 of the membrane 50 closes the radial openings 36 and the depression which is created in the pumping chamber 34 causes the flexible lip 53 to separate from the skirt interior 20 and a product inlet from the container.

The recess 71 is located above the upper end of the openings radial 36 so that when the push button 5 returns, the surface 72 of the central part 51 can close the radial openings 36.

The product reaches the pumping chamber 34 by flowing through the grooves 25 of the inner skirt 20 along the central part 51 of the membrane 50, crossing the inner skirt 20 in favor of the openings 22, then bypassing the flexible lip 53 and going up outside of the latter, as illustrated in Figure 10.

As the push button 5 goes up, air can reach the container through the clearance between the guide skirt 16 and the tubular skirt 33 and through the return orifice air 42, until the sealing lip 37 is applied again so watertight on the guide skirt 16 when the push button 5 reaches the high position, as explained above.

It will be noted that the relatively small thickness of the bottom 52 makes it possible to prevent the elastomeric material in which the membrane is made does not constitute, under the action from the thrust of the central duct 32, a bead which when applied to the surface interior of the interior skirt 20 could cause detrimental friction to the correct operation of the pump.

Of course, the invention is not limited to the embodiment which comes to be described.

One can in particular use a membrane whose radially inner surface of the upper part of the central part would be symmetrical in revolution, the bosses 55 being replaced by bosses 60 made at the upper part of the central duct 32, as illustrated in FIGS. 11 and 12.

We can still assist or cause the return movement of the push button by means of a helical spring 90 shown in broken lines on the figure 10.

This spring is housed inside the inner skirt 20, works in compression, and is supported at its lower end on the recess 26 and at its upper end on the underside of the bottom 52 of the membrane.

We can still place a valve upstream of the membrane, this valve opening when product is drawn into the pumping chamber and having a leakage so as not to prevent the moving member from moving during the distribution of a dose of product.

This valve can be produced for example by means of a ball 91 shown in broken lines in Figure 10, the tip 12 serving as a seat.

Reliefs 92 are produced on the inner surface of the inner skirt to retain ball 91 near its seat.

The ball 91 is chosen very rough so as to create a leak allowing not to block the downward movement of the central part of the membrane during dispensing a dose of product.

The ball 91 makes it possible to prime the pump by actuating a small number of times the push button.

The membrane can also be made of at least two materials different.

Thus, to make the flexible lip 53, a material more soft than that used to produce the spring portion 51.

We can use for example the same elastomer, but more or less charge.

The fact of using different materials makes it possible to use a material relatively hard for the central part 51, which is favorable for a good spring effect without interfering with the operation of the flexible lip 53.

In an embodiment not illustrated, a helical spring is arranged around the central duct and bears at its lower end on the upper end of the membrane and at its upper end on the push button 5.

Claims (37)

1. A pump of type comprising a moving member (5) mounted to move relative to a support (4), the moving member having a central duct (32) into which the substance to be dispensed penetrates via at least one opening (36), the support co-operating with the moving member to define a variable volume pump chamber (34) around said central duct, the pump also having a diaphragm (50) having a central portion (51) in the form of a sleeve that is open at its top end and closed at its bottom end, said central duct (32) being inserted in said central portion, the diaphragm being organized in such a manner as to isolate the opening(s) (36) of the pump chamber when the volume of the pump chamber increases and the substance is sucked into it, the pump chamber being isolated from the source of substance when the volume of said pump chamber decreases, the pump being characterized by the fact that the bottom portion of the central portion (51) of the diaphragm (50) presents, at least over a sector (77) of its periphery, a preferred deformation zone (78).
2. A pump according to claim 1, characterized by the fact that said preferred deformation zone is constituted by a thin zone (78).
3. A pump according to claim 2, characterized by the fact that the bottom portion of the central portion (51) of the diaphragm (50) has at least two diametrically opposite thin zones (78).
4. A pump according to claim 2 or 3, characterized by the fact that the thin zone (78) is formed by reducing the thickness of the diaphragm by at least 20%, and preferably by at least 25%.
5. A pump according to any preceding claim, characterized by the fact that the inside surface of the central portion of the diaphragm presents an inwardly-directed step (71).
6. A pump according to the preceding claim, characterized by the fact that said step (71) is situated level with the top end of the preferred deformation zone(s) (78).
7. 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 (34) from the source of substance when the volume of said pump chamber (34) decreases, and secondly for enabling substance to enter into said pump chamber (34) when the volume thereof increases.
8. A pump according to the preceding claim, characterized by the fact that said flexible lip (53) is connected to the central portion (51) of the diaphragm (50) by forming a downwardly open annular trough (54), and by the fact that the support includes an inner skirt (20) having its top end bearing against the end wall of said trough (54) to retain the diaphragm when the moving member (5) is moved downwards to decrease the volume of the pump chamber (34).
9. A pump according to claim 8, characterized by the fact that the inner skirt (20) is a portion of a piece fitted to the remainder of the support.
10. A pump according to the preceding claim, characterized by the fact that the support has a pair of sealing lips (24) bearing in leakproof manner on a tubular skirt (33) of the moving member, said tubular skirt (33) being downwardly open and extending around the central duct (32) concentrically thereabout, said tubular skirt (33) also defining the pump radially outer wall of the pump chamber (34).
11. A pump according to the preceding claim, characterized by the fact that the tubular skirt (33) of the moving member slides inside a guide skirt (16) of the support, co-operating with the inner skirt (20) of the support to define an upwardly open annular trough which communicates with the source of substance via at least one air intake orifice (42), the tubular skirt (33) of the moving member bearing in leakproof manner against said guide skirt (16) when the moving member is at rest and the volume of the pump chamber (34) is at a maximum.
12. A pump according to either one of the two preceding claims, characterized by the fact that said inner skirt (20) has openings (22) at its top end, the openings being of a height that is less than the height of the flexible lip (53), said openings (22) enabling the substance to reach the pump chamber (34) when the volume thereof increases and the flexible lip (53) moves away from the inner skirt (20) under the effect of the depression in the pump chamber (34).
13. A pump according to any one of the five preceding claims, characterized by the fact that the height of the flexible lip (53) is greater than or equal to the height of the central portion (51) of the diaphragm, prior to the diaphragm being assembled in the pump.
14. A pump according to any one of the six preceding claims, characterized by the fact that the flexible lip (53) is of thickness that increases going towards the top end of the diaphragm.
15. A pump according to any one of the seven preceding claims, characterized by the fact that the outside surface of the flexible lip (53) presents, starting from its bottom end, a bottom portion (81) that is circularly cylindrical about the axis (X) of the central portion (51) of the diaphragm, followed by an upper portion (82) that is conical and diverges towards the top end of the diaphragm, which upper portion (82) is connected via a shoulder (83) to an annular rib (84).
16. A pump according to any one of the eight preceding claims, characterized by the fact that the inside diameter of the flexible lip (53) is equal to the outside diameter of the inner skirt (20), ignoring manufacturing tolerances.
17. A pump according to the preceding claim, characterized by the fact that the clearance between the flexible lip (53) and the inner skirt (20) is negative or zero.
18. A pump according to any preceding claim, characterized by the fact that the central portion (51) of the diaphragm (50) is connected at its top end to an annular portion (85) whose width and thickness are selected in such a manner as to improve retention of the diaphragm when said central portion (51) is stretched.
19. A pump according to the preceding claim, characterized by the fact that the thickness of said annular portion (85), prior to the diaphragm (50) being assembled in the pump, is greater than or equal to the thickness of the diaphragm in its central portion.
20. A pump according to either one of the two preceding claims, characterized by the fact that said annular portion (85), prior to the diaphragm (50) being assembled in the pump, is at least 1.5 times wider than it is thick, and preferably twice as wide as it is thick.
21. A pump according to any preceding claim, characterized by the fact that the end wall (52) of the central portion (51) of the diaphragm (50), prior to the diaphragm being assembled in the pump, presents the same thickness as the side wall of the central portion of the diaphragm outside said preferred deformation zone(s) (78).
22. A pump according to any preceding claim, characterized by the fact that the thickness of the end wall (52) of the central portion (51) of the diaphragm (50) corresponds to within 20% to the thickness of the side wall of the central portion of the diaphragm outside said preferred deformation zone(s) (78), prior to the diaphragm being assembled in the pump.
23. A pump according to any preceding claim, characterized by the fact that when the moving member (5) is at rest, the length of the central portion of the diaphragm after being assembled in the pump is greater than or equal to 1.5 times its initial length ( l ₀) prior to assembly in the pump, and is preferably greater than or equal to twice said initial length, and more preferably greater than or equal than 3 times said initial length.
24. A pump according to any preceding claim, characterized by the fact that when the moving member is fully depressed, the length of the central portion (51) of the diaphragm is greater than or equal to twice the initial length ( l ₀) of the diaphragm prior to assembly in the pump, is preferably greater than or equal to 3 times said initial length, and more preferably greater than or equal to 4 times said initial length.
25. A pump according to any preceding claim, characterized by the fact that at least one of the diaphragm and the central duct (32) is shaped to prevent an annular zone forming between the diaphragm and the central duct that would prevent the substance contained in the pump chamber from flowing via said central duct (32) when the volume of the pump chamber decreases.
26. A pump according to the preceding claim, characterized by the fact that at least one of the diaphragm and the central duct is shaped so as to bear against the other of the central duct and the diaphragm at predetermined locations of its periphery, at least one of the diaphragm and the central duct having portions in relief against which the other of the central duct and the diaphragm comes to bear, at least during displacement of the moving member relative to the support.
27. A pump according to the preceding claim, characterized by the fact that said portions in relief are made on the diaphragm, preferably being constituted by bulges (55) uniformly distributed around the axis (X) of the central portion (51) of the diaphragm at its opening, said bulges (55) extending over the top face of the diaphragm.
28. A pump according to any preceding claim, characterized by the fact that the central duct (32) of the moving member is provided with at least one radial opening (36) at its bottom end.
29. A pump according to any preceding claim, characterized by the fact that the moving member constitutes a pushbutton, the central duct (32) being integrally formed with a dispenser endpiece (35).
30. A pump according to any preceding claim, characterized by the fact that the diaphragm is made of a nitrile elastomer or of a silicone elastomer.
31. A pump according to any preceding claim, having a return spring for returning the moving member towards an initial position after a quantity of substance has been dispensed.
32. A pump according to the preceding claim, characterized by the fact that the return spring is constituted by a helical spring working in compression.
33. A pump according to the preceding claim, characterized by the fact that the spring is disposed on the axis of the membrane so that the top end of the spring bears against the bottom end of the central portion of the membrane.
34. A pump according to any preceding claim, including a non-return valve upstream from the membrane, said valve opening while substance is being sucked into the pump chamber, and presenting a leak so as to avoid preventing displacement of the moving member while a quantity of substance is being dispensed.
35. A pump according to any preceding claim, characterized by the fact that the membrane is made of at least two different materials.
36. A pump according to claims 7 and 36, characterized by the fact that the flexible lip (53) is made of material softer than the spring-forming portion (51) of the membrane.
37. A receptacle fitted with a pump as defined in any preceding claim.

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