EP0470906A1 - Precompression-dosing pump having improved efficiency by allowing early take in of fluid into the pump chamber - Google Patents

Abstract

A pump of the prior art enables a liquid product to be discharged in the form of sprayed particles by virtue of the precompression of the metered quantity delivered. For this purpose, in addition to the usual components of a piston pump, there is provided a particular differential piston (4). It comprises, in fact, on the one hand, a rod (41) suitable for closing the outlet valve of the pump chamber (23) by bearing against a seat (32) carried by the actual piston (3) of the pump and, on the other hand, a skirt (42) suitable for closing the inlet valve of the chamber (23) and fitting around an open cylinder (24) integral with the pump body (2). The skirt (42) has a larger diameter than the rod (41) so that it is attached to the latter by means of an annular shoulder (44). <??>According to a known principle, the admission into the pump chamber (23) is moreover hastened by virtue of the disposition on the differential piston (4) of a borehole (63) which establishes a communication between the inside of the skirt (42) and the shoulder (44). A cylindrical shutting element (60) is then slipped around the rod (41) with a view to being applied against the said shoulder (44) at the level of two annular contacts (64, 65) between which the borehole (63) emerges. It enables the said borehole (63) to be closed during the discharge of the metered quantity of precompressed product. <??>So as to make this closing-off more systematic, the present improvement teaches a structure for the shutting-off element (60) such that, especially when the pump is at rest, it is maintained deformed and therefore is applied to the said shoulder (44) with a force sufficient to ensure the seal between the said two annular contacts (64, 65). <IMAGE>

Description

The present invention relates to a precompression dosing pump of the prior art for emitting an essentially liquid product in the form of an aerosol. More precisely, it relates to an improvement of this pump which notably improves its efficiency (defined by the ratio of the volume of the dose emitted to the volume of the pump chamber). This improvement in fact ensures almost complete filling of the pump chamber by allowing the product to be sucked in there from the first moments of the pump pistons rising. This mechanism also operates here with great reliability.

In truth, the process of improving the yield in question here has in itself been known for several years. However, it has been put into practice thanks to more or less happy systems. In order to clearly understand what their shortcomings are, we will first of all come back to the precompression dosing pump of the prior art which they have in turn sought to make more efficient. For this, we will refer to the longitudinal section shown in Figure 1 of the drawings attached to this memo.

Figure 1 shows in fact a precompression dosing pump designed according to the principle of the invention of Rudolph Albert described in French patent FR 1 486 396 filed in 1966. This also involves an intake valve more interesting, the design of which is set out in the addition certificate FR 2 305 241 filed in 1975 by the company STEP (Technical Spray Company). Thus this pump comprises in known manner five cylindrical parts intended to be mounted so that their respective axes of revolution are combined. In FIG. 1, the axis of the assembly is arranged vertically, the intake of the breast of the pump being carried out from the bottom from a reservoir not shown while the emission into the open air takes place by the top.

• une tourette 1 dont l'empattement 11 inférieur permet l'assujettissement de la pompe au réservoir de produit à émettre,
• un corps 2 creux à une extrémité ouverte 21 duquel la tourette 1 précédente s'encliquette tandis qu'à son autre extrémité, une douille 22 permet de raccorder la pompe à un tube plongeur non représenté,
• un premier piston 3 monté coulissant à l'intérieur du corps 2 creux et délimitant avec ce dernier la chambre 23 de pompe. Ce premier piston 3 se prolonge vers le haut en une tige 31 creuse comportant, à mi-hauteur, un siège 32 de soupape,
• un second piston 4, plutôt appelé ci-dessous piston différentiel 4, monté coulissant à l'intérieur du corps 2 creux au sein de la chambre 23 de pompe. Le piston différentiel 4 se prolonge vers le haut par une tige 41 de soupape s'engageant dans la tige 31 creuse précédente pour reposer contre le siège 32 de soupape. Vers le bas, il se termine par une jupe 42 comportant à son extrémité inférieure une lèvre 43 d'étanchéité. Elle est destinée à collaborer avec un cylindre 24 creux solidaire du corps 2 de pompe sur lequel la jupe 42 peut venir s'emmancher,
• et enfin, un ressort 5 de rappel disposé entre la base du corps 2 de pompe et le piston différentiel 4.

The five parts of the pump are:

• a tower 1 whose lower wheelbase 11 allows the pump to be secured to the reservoir of product to be emitted,
• a hollow body 2 at one open end 21 from which the preceding tower 1 clicks in while at its other end, a socket 22 makes it possible to connect the pump to a plunger tube not shown,
• a first piston 3 mounted sliding inside the hollow body 2 and delimiting with the latter the pump chamber 23. This first piston 3 extends upwards into a hollow rod 31 comprising, at mid-height, a valve seat 32,
• a second piston 4, rather called below differential piston 4, mounted to slide inside the hollow body 2 within the pump chamber 23. The differential piston 4 is extended upwards by a valve rod 41 engaging in the rod 31 hollow previous to rest against the valve seat 32. Downwards, it ends in a skirt 42 having at its lower end a sealing lip 43. It is intended to collaborate with a hollow cylinder 24 secured to the pump body 2 on which the skirt 42 can be fitted,
• and finally, a return spring 5 disposed between the base of the pump body 2 and the differential piston 4.

These five parts, shown in the pump's rest position in FIG. 1, collaborate as follows. When the user of the pump presses on the hollow rod 31 of the first piston 3 (for example by means of a push button not shown), it causes the first piston 3 to descend into the body 2 of the pump. The piston 3 drives the differential piston 4 in its movement, its valve stem 41 being held against the valve seat 32 by means of the spring 5. Consequently, thanks to the guidance offered by the external fins 46 of the skirt 42, the sealing lip 43 is applied against the external surface of the hollow cylinder 24 and thus isolates the pump chamber 23 from the reservoir. At the same time, the volume of the latter decreases so that the product it contains sees its pressure increase. When its value reaches a so-called precompression threshold in relation to the stiffness of the spring 5, the conformation of the differential piston 4 (and in particular the existence of the large shoulder 44 at the base of the valve stem 41) causes the withdrawal of the valve stem 41 out of valve seat 32. The product under pressure then leaks through the channel 33 inside the hollow rod 31. The emission continues until the differential piston 4 comes into abutment against the hollow cylinder 24 at the level of an end-of-travel recess 45 carried internally by its skirt 42.

It is then that, the volume of the pump chamber 23 ceasing to decrease, the pressure of the product which it contains drops. This pressure is no longer able to oppose the spring 5 so that the valve rod 41 returns against its seat 32 and closes the passage to the outside. The user then stops pressing on the rod 31 and the spring 5 causes the two pistons to rise within the pump body 2. It follows the increase in the volume of the pump chamber 23. However, the sealing lip 43 does not immediately leave the exterior surface of the hollow cylinder 24. During this time interval, the completely isolated pump chamber 23 is placed under vacuum. Also, as soon as the lip 43 leaves the cylinder 24, a strong suction causes the product contained in the reservoir to enter the chamber 23 via the sleeve 22

It is this last phase of filling the pump chamber 23 which largely determines the efficiency. In order for it to approach 1, it is indeed necessary for almost all of the chamber 23 to be ultimately occupied by product. Gold, in the prior art pump shown in Figure 1, this condition is almost never fulfilled. Indeed, a significant depression develops within the chamber 23 while the sealing lip 43 of the skirt 42, still in contact with the cylinder 24, circulates along the latter. Often, it is so strong that it causes the suction of outside air at the peripheral lips 34 of the first piston 3. Consequently, the volume of the chamber 23 occupied by the air is lost for the product.

Depending on the point of view, this phenomenon results in various drawbacks. First of all, the quantity of air drawn in being uncontrollable, the additional volume of the pump chamber, which is occupied by the product and which constitutes the dose emitted in fine, is itself irregular. Then, if a precise minimum dose has to be ensured, a larger pump chamber should be provided, ie a larger pump body. Finally, in an attempt to reduce the air intake, the first piston 3 must be provided with more watertight peripheral lips 34. They then cause greater friction of the first piston 3 against the pump body 2 so that a less flexible spring 5 must be used. In all cases, the pump market is more restricted due to its irregularity, its size or its difficulty in actuation.

In order to remedy this defect in the precompression dosing pump of the prior art, several arrangements have been devised. All of them aim to avoid the development of too strong a depression within the pump chamber with the resulting undesirable air suction. For this, they seek to establish communication as soon as possible between the product reservoir and the chamber as soon as the rise of the pistons determines the increase in volume of the latter.

For this purpose, American patent US Pat. No. 4,089,442 filed by Hafele et al. in 1976, provided for several bores within the differential piston 4 in the form of small cylindrical holes connecting the interior of the skirt 42 and the surface of the shoulder 44. On this latter surface, there is also a flange mounted sliding on the valve rod 41. The bores and the flange are then assumed to behave in the manner of a non-return valve, the flange sealing off the bores or, on the contrary, peeling off according to whether the pressure in the pump chamber is above or below atmospheric pressure. In practice, this valve does not work systematically. It suffices for example that the collar is placed a little at an angle around the valve stem 41. It then locks in a more or less open position which, if it does not prevent, at least slows down the pressurization of the pump chamber and therefore the emission of product to the outside.

Thus in 1984, VALOIS filed the French patent FR 2,558,214 eliminating the collar. Instead, the bores are terminated by a thinned, slit-shaped boss. By their elasticity, the lips of the slot then act directly as a non-return valve. This system, which is more efficient than the previous one, nevertheless has a drawback. To be able to make the bosses, a fairly rigid plastic material should be used. Consequently, the opening of the slots during the intake phase into the pump chamber still requires that a fairly high vacuum prevails there. The problems associated with the intake of outside air are therefore not completely eliminated.

Also the VALOIS company imagined at the beginning of 1988 a skirt 42 in two parts with a link with lost movement. This is described in French patent FR 2 631 564. As long as the pistons descend, the two parts of the skirt 42 fit into each other in a leaktight manner. The lost movement connection, on the other hand, allows the creation of a passage from the interior of the skirt 42 to the pump chamber 23 when the pistons are raised, the sealing lip 43 rubbing against the cylinder 24 and s' thus opposing the ascent of one of the parts of the skirt 42. In this case, the putting into practice does not reveal any failure. Rather, it is the manufacturing and verification sampling of the two parts of the skirt and their connection that make the cost of the pump prohibitive.

The present invention addresses the same problem as the three patents which have just been mentioned. It solves it, in turn, so that the precompression metering pumps thus perfected operate without risk while remaining inexpensive.

• une tourette creuse,
• un corps creux comportant deux extrémités ouvertes, ladite tourette étant fixée à une première extrémité dudit corps creux tandis qu'un cylindre creux ayant une section ouverte prolonge intérieurement une seconde extrémité dudit corps creux,
• un premier piston monté pour coulisser de façon étanche à l'intérieur dudit corps creux entre une première et une seconde positions, ledit premier piston venant s'appliquer contre ladite tourette dans ladite première position, une tige creuse prolongeant ledit premier piston vers ladite première extrémité dudit corps creux et comportant intérieurement un siège de soupape,
• un piston différentiel monté coulissant à l'intérieur dudit corps creux et comportant un épaulement du côté de ladite première extrémité dudit corps creux, ledit piston différentiel se prolongeant vers ladite première extrémité dudit corps creux par une tige de soupape s'engageant dans ladite tige creuse dudit premier piston pour collaborer avec ledit siège de soupape, ledit piston différentiel se prolongeant vers ladite seconde extrémité dudit corps creux par une jupe ayant une surface extérieure de guidage et une surface intérieure munie d'un décrochement ainsi que d'une lèvre d'étanchéité, ladite lèvre d'étanchéité s'emmanchant autour dudit cylindre creux au moins aussitôt que ledit premier piston quitte ladite première position, ladite seconde position dudit premier piston étant atteinte lorsque ladite section ouverte dudit cylindre creux entre en butée contre ledit décrochement de ladite surface intérieure de ladite jupe,
• un ressort de rappel disposé enae ledit piston différentiel et ladite seconde extrémité dudit corps creux,

ledit piston différentiel comportant en outre au moins un alésage partant de ladite surface intérieure de ladite jupe et débouchant sur ledit épaulement, un élément d'obturation cylindrique enfilé autour de ladite tige de soupape étant adapté à s'appliquer contre ledit épaulement au niveau de deux contacts annulaires entre lesquels débouche ledit alésage de façon à former un clapet anti-retour à l'embouchure dudit alésage et un espace libre étant ménagé autour dudit épaulement de sorte que ledit élément d'obturation peut se décoller dudit épaulement, CARACTERISE EN CE QUE, notamment lorsque ladite pompe-doseuse est au repos, ledit élément d'obturation est maintenu déformé de sorte qu'il s'applique sur ledit épaulement avec une force suffisante pour garantir l'étanchéité desdits deux contacts annulaires.For this, an improvement has been developed which improves the efficiency of a precompression dosing pump, said dosing pump making it possible to issue a product under pressure thanks to the collaboration of five cylindrical parts with a common axis:

• a hollow tower,
• a hollow body having two open ends, said spinner being fixed to a first end of said hollow body while a hollow cylinder having an open section internally extends a second end of said hollow body,
• a first piston mounted to slide in leaktight manner inside said hollow body between a first and a second position, said first piston pressing against said spinner in said first position, a hollow rod extending said first piston towards said first end of said hollow body and internally comprising a valve seat,
• a differential piston slidably mounted inside said hollow body and comprising a shoulder on the side of said first end of said hollow body, said piston differential extending towards said first end of said hollow body by a valve rod engaging in said hollow rod of said first piston to collaborate with said valve seat, said differential piston extending towards said second end of said hollow body by a skirt having a outer guide surface and an inner surface provided with a recess as well as a sealing lip, said sealing lip fitting around said hollow cylinder at least as soon as said first piston leaves said first position, said second position said first piston being reached when said open section of said hollow cylinder comes into abutment against said recess of said inner surface of said skirt,
• a return spring arranged in said differential piston and said second end of said hollow body,

said differential piston further comprising at least one bore extending from said inner surface of said skirt and opening onto said shoulder, a cylindrical closure element threaded around said valve stem being adapted to be applied against said shoulder at two annular contacts between which opens said bore so as to form a non-return valve at the mouth of said bore and a free space being provided around said shoulder so that said closure element can be detached from said shoulder, CHARACTERIZED IN THAT, in particular when said metering pump is at rest, said closure element is kept deformed so that it is applied to said shoulder with sufficient force to guarantee the tightness of said two annular contacts.

More specifically, a first of said two annular contacts between said closure element and said shoulder is formed on a support cord projecting on said shoulder between said bore and said outer surface of said skirt, a second of said two annular contacts being made on a surface of said shoulder located in the immediate vicinity of said valve stem and recessed with respect to said support bead, said first contact being broken during the opening of said non-return valve at the mouth of said bore while said second contact is permanently maintained, said free space provided around said shoulder being adapted to allow the folding of said closure element towards said valve stem while said first contact is broken.

• a/ ladite tige de soupape, ledit trou central dudit joint ayant un diamètre inférieur à celui de ladite tige de soupape de sorte que l'enfilage dudit joint sur ladite tige de soupape provoque un gauchissement dudit joint;
• b/ un relief de ladite tige de soupape situé à une distance telle dudit épaulement dudit piston différentiel qu'une fois enfilé autour de ladite tige de soupape, ledit joint est maintenu par coincement au niveau dudit trou central entre ledit relief et ledit épaulement.

According to a first advantageous embodiment of the present improvement, said closure element is an elastomer seal having a central hole and an outer periphery. In particular when said metering pump is at rest, it is kept deformed by:

• a / said valve stem, said central hole of said seal having a diameter smaller than that of said valve stem so that threading of said seal on said valve stem causes warping of said seal;
• b / a relief of said valve stem located at such a distance from said shoulder of said differential piston that once threaded around said valve stem, said seal is held by wedging at said central hole between said relief and said shoulder.

Then, said free space formed around said shoulder is rather constituted by an annular recess of said first piston.

According to a second advantageous embodiment of the present improvement, said closure element is a plastic ring having a central hole extended on one side by a hollow cylindrical sleeve which is adapted to be threaded around said valve stem and has one end open. In particular when said dosing pump is at rest, said valve seat of said first piston is applied to said open end and axially presses said sleeve against said surface of said shoulder in close proximity to said valve stem. Preferably, said open end of said sleeve comprises at least one notch, so that its presence does not hinder the passage of the product. It is advantageously bevelled so that there is automatic centering of said first piston on said sleeve.

When the closure element is a ring integral with a hollow cylindrical sleeve, the latter advantageously comprises at least two internal annular reliefs, said valve stem then comprising at least one external annular relief intended to take place with a compatible axial clearance with the tolerance of the parts between said two annular reliefs of said sleeve. Said annular reliefs of said sleeve are preferably located at a section of said sleeve enlarged relative to said open end. In the same case, said free space formed around said shoulder is rather constituted by a cylindrical recess having for axis of revolution said common axis of said parts of said metering pump, said recess extending from said valve seat and having a widening at the level of the enlargement of said sleeve.

In a simple manner, said bore is a cylindrical channel with an axis parallel to said common axis of said parts of said precompression metering pump. Said recess of said inner surface of said skirt is preferably notched so as to release the start of said bore.

There may be two or three bores in said differential piston. They are then molded with said differential piston.

Advantageously, said first piston slides in leaktight manner inside said hollow body thanks to a single peripheral sealing lip oriented towards the pump chamber.

If necessary, said closure element is produced by molding.

• faible encombrement grâce à un rendement pratiquement égal à 1,
• réduction des frottements du piston 3 contre le corps 2, une seule lèvre 34 étant désormais suffisante. D'où un ressort 5 de rappel d'autant plus souple que la dépression à vaincre est également diminuée, et un effort d'actionnement du piston 3 plus réduit (par exemple passant de 2,8 kg à 2,1, voire 2,0 kg).

The precompression dosing pump comprising the present improvement then has all the expected advantages of early communication between the reservoir and the pump chamber in the process of increasing in volume:

• small footprint thanks to a yield practically equal to 1,
• reduction of friction of the piston 3 against the body 2, a single lip 34 is now sufficient. Hence a return spring 5 which is all the more flexible as the depression to be overcome is also reduced, and a more reduced actuation force of the piston 3 (for example passing from 2.8 kg to 2.1 or even 2, 0 kg).

The thus improved metering pump has further advantages when used in conjunction with a vacuum tank. It is however suitable for this that the respective lengths of said hollow cylinder and of said skirt of said differential piston are such that said sealing lip always remains fitted around said hollow cylinder even when said first piston is in said first position, communication with the pump chamber therefore being possible only by said at least one bore formed in said differential piston.

In fact, when the product contained in the vacuum tank has started to be used up, the walls of the tank must deform to adapt to the decrease in interior volume. However, there is always a certain mechanical resistance with respect to this deformation so that very quickly, the tank is the place of a relative depression. The latter is likely to cause suction of the outside air by any contact in the pump whose sealing would not be perfect. This is particularly the case of the contact between its piston 3 and its body 2 especially when the pump has aged a little and its material has crept. It follows the penetration of outside air into the pump chamber 23.

Provided that the skirt 42 of the differential piston 4 remains fitted around the hollow cylinder 24, the chamber 23 therefore no longer communicates with the reservoir except by the non-return valve produced according to the invention at the bores 63 of the differential piston 4. Thus the product contained in the reservoir does not risk being brought into contact with the air which has entered the chamber 23 as has just been said. This result is particularly interesting when the good conservation of the product requires to keep it far from the ambient air which could soil it, oxidize it, etc.

• la figure 1 est une coupe longitudinale d'une pompe-doseuse à précompression de l'art antérieur montrée en position de repos;
• les figures 2 à 5 sont des coupes longitudinales de la pompe-doseuse à précompression de la figure 1, mais comportant cette fois une première forme de réalisation du présent perfectionnement. Cette pompe est montrée en position de repos sur la figure 2, en phase d'amorçage sur la figure 3, lors de l'émission du produit sur la figure 4 et pendant le remplissage de la chambre de pompe sur la figure 5;
• les figures 6 et 7 sont des détails respectivement des figures 2 et 5. Elles montrent avec plus de précision la première forme de réalisation du présent perfectionnement évoquée ici ;
• la figure 8 est une coupe longitudinale de la pompe-doseuse à précompression de la figure 1, mais comportant cette fois une deuxième forme de réalisation du présent perfectionnement. La pompe est montrée au repos;
• les figures 9 et 10 sont des détails montrant avec plus de précision la deuxième forme de réalisation du présent perfectionnement évoquée ici. Il s'agit également de coupes longitudinales correspondant respectivement à la phase d'émission du produit et à la phase d'admission dans la chambre de pompe; et
• la figure 11 est une coupe longitudinale d'une autre pompe-doseuse à précompression comportant le présent perfectionnement. Cette dernière est destinée à être employée avec un réservoir sous vide.

We will describe below exemplary embodiments of the present invention which are illustrated by the accompanying drawings. On these:

• Figure 1 is a longitudinal section of a precompression metering pump of the prior art shown in the rest position;
• Figures 2 to 5 are longitudinal sections of the precompression dosing pump of Figure 1, but this time comprising a first embodiment of the present improvement. This pump is shown in the rest position in FIG. 2, in the priming phase in FIG. 3, during the emission of the product in FIG. 4 and during the filling of the pump chamber in FIG. 5;
• Figures 6 and 7 are details respectively of Figures 2 and 5. They show with more precision the first embodiment of the present improvement mentioned here;
• Figure 8 is a longitudinal section of the precompression metering pump of Figure 1, but this time comprising a second embodiment of the present improvement. The pump is shown at rest;
• Figures 9 and 10 are details showing more precisely the second embodiment of the present improvement mentioned here. They are also longitudinal sections corresponding respectively to the phase of emission of the product and to the phase of admission into the pump chamber; and
• Figure 11 is a longitudinal section of another precompression metering pump comprising the present improvement. The latter is intended to be used with a vacuum tank.

• 1/le piston différentiel 4 est désormais muni d'au moins un alésage 63 faisant communiquer l'intérieur de la jupe 42 avec la surface de l'épaulement 44. Cet alésage 63 admet en l'occurrence la forme d'un petit trou cylindrique d'axe vertical. En outre, le décrochement 45 de fin de course porté intérieurement par la jupe 42 est échancré localement. Ainsi l'alésage 63 n'est-il pas totalement obvié par le ressort 5 qui prend appui à l'intérieur de la jupe 42 ;
• 2/le piston 3 admet inférieurement un évidement 35 en forme de couronne. Par ailleurs, il ne reste plus qu'une lèvre d'étanchéité 34 périphérique. Cette dernière se prolonge axialement par de simples ailettes 36 de guidage;
• 3/un joint 60 annulaire entoure la racine de la tige 41 de soupape et s'applique contre l'épaulement 44 du piston différentiel 4.

In the following paragraphs, we will focus on this development. In fact, it only concerns the two pistons of the precompression dosing pump of the prior art. To be convinced, let's compare for example Figure 1 which shows the latter and Figure 2 where is shown the same pump provided with a first embodiment of the present improvement. Three modifications then appear mainly. We review them here with more reference to Figure 6 in detail:

• 1 / the differential piston 4 is now provided with at least one bore 63 communicating the interior of the skirt 42 with the surface of the shoulder 44. This bore 63 admits in this case the shape of a small cylindrical hole vertical axis. In addition, the end-of-travel step 45 carried internally by the skirt 42 is locally notched. Thus, the bore 63 is not completely obviated by the spring 5 which bears on the inside of the skirt 42;
• 2 / the piston 3 admits a recess 35 in the form of a crown. Furthermore, there remains only one peripheral sealing lip 34. The latter is extended axially by simple guide fins 36;
• 3 / an annular seal 60 surrounds the root of the valve stem 41 and is applied against the shoulder 44 of the differential piston 4.

Rather than these three arrangements which are found in certain systems for improving the yield of the prior art, the present improvement according to the first embodiment is essentially due to the connection produced between the seal 60 and the differential piston 4. In fact, the seal 60 is cut from an elastomer so that its central hole initially admits a diameter smaller than that of the valve stem 41. Thus, its threading around the valve stem 41 implies a deformation of the seal 60. This results in warping of its surface. The resulting concavity is also oriented towards the end of the rod 41 by virtue of two reliefs presented by the surface of the differential piston 4. One of these reliefs (bearing the reference 61) surrounds the rod 41 at a distance such as the shoulder 44 that the seal 60 can be trapped by it. The other relief (bearing the reference 64) is carried by the surface of the shoulder 44 between the bore 63 and the peripheral guide fins 46. It forms a support bead for the seal 60.

The deformation which is thus imposed prior to the joint, unlike similar systems of the prior art, results in a theoretically perfectly reproducible operation. In fact, when the pump is at rest and therefore the pressures prevailing around the joint are identical, the preformed elastomer seeks to return to its original shape. In doing so, it is applied by itself against the support cord 64 and exerts a slight force on the latter. Thus the valve which it forms at the upper mouth of the bore 63 is closed in advance as shown in FIGS. 2 and 6.

When the first piston 3 is depressed by the user, everything then happens as in the unperfected precompression dosing pump. Indeed, the increase in pressure which then develops in the pump chamber 23 only reinforces the application of the seal 60 against the bead 64 of support and therefore the sealing of this closure. Furthermore, the jamming of the seal 60 between the relief 61 and the shoulder 44 seals at the surface 65 of the shoulder 44 located at the root of the valve stem 41. In the priming phase (see FIG. 3), the compressible air contained in the pump chamber 23 allows the pistons to be pushed in until the notched recess 45 abuts against the hollow cylinder 24 of the body 2. The air is for example discharged into the reservoir of product to be emitted thanks to the gadroon 25 which locally lifts the lip 43 of the skirt 42. When the product is emitted (see FIG. 4), the pressure of the latter ends up actuating differential piston 4, the rod 41 of which is withdrawn from the valve seat 32.

It is only when the pump chamber 23 has been emptied that the valve formed by the bore 63 and the seal 60 opens. Indeed, while the chamber 23 increases in volume, the depression of which it is the seat does not take long to raise the seal 60. As indicated in FIG. 5 and, with more details, in FIG. 7, the outer periphery of the seal 60 then comes off the support cord 64. Thanks to the annular recess 35 of the piston 3, the seal 60 is not hampered in its pivoting movement. The product is therefore sucked from inside the skirt 42 to the pump chamber 23 passing through the bore 63 (cf. the arrows in FIG. 7). It should be noted that the lifting of the seal 60 is also facilitated by the prior deformation which is imposed on it. This can indeed be such that the pressure force exerted by the seal 60 against the support cord 64 is relatively low. A slight depression is therefore enough to overcome it.

Finally, as soon as the pump chamber 23 is again filled, the seal 60 resumes its place against the support cord 64. Its jamming at the root of the valve stem 41 is indeed the guarantee of this return which therefore ceases to be random. It is also carried out almost instantaneously.

A second embodiment of the present improvement uses, instead of the elastomeric seal, a plastic ring. The pump thus improved can then be presented as illustrated in FIG. 8. The corresponding longitudinal section is comparable to that of FIG. 2 relating to the first embodiment of the present improvement. Also, elements playing similar roles in the operation of these two embodiments have they received identical reference numbers.

• 1/ le piston différentiel 4 comporte par exemple le même alésage 63 que celui de la première forme de réalisation évoquée ici. En d'autres termes, il s'agit d'un petit du cylindrique créant une communication entre l'intérieur de la jupe 42 et la surface de l'épaulement 44. Une échancrure locale du décrochement 45 de fin de course porté intérieurement par la jupe 42 est également prévue de façon que le ressort 5 n'obture pas cette communication ;
• 2/ non seulement la base du piston 3 est cette fois évidée, mais aussi la parbe du canal 33 intérieur de la tige 31 creuse qui se trouve en amont du siège 32 de soupape. Il s'ensuit un espace 35 de forme un peu plus complexe. Par exemple, le canal 33 intérieur du piston 3 s'élargit à présent à deux reprises (si nous le considérons en sens inverse de l'écoulement du produit). Le premier élargissement n'est autre que le siège 32 de soupape de la pompe de l'art antérieur. S'y ajoute désormais un second élargissement 37. Il se situe à peu près à mi-hauteur entre le siège 32 et la base du piston 3.
  Pour ce qui est des lèvres d'étanchéité du piston 3 qui isolent la chambre 23 de pompe au niveau du corps 2 de pompe, seule la lèvre 34 orientée vers la chambre 23 demeure comme dans la première forme de réalisation étudiée ci-dessus. La lèvre supérieure existant dans la pompe non perfectionnée est encore plutôt remplacée par des ailettes 36 de guidage.
• 3/ une bague 60 est, dans cette deuxième forme de réalisation du présent perfectionnement, disposée contre l'épaulement 44 du piston 4 différentiel pour faire office de clapet anti-retour. Elle est solidaire d'un manchon 66 entourant la tige 41 de soupape qui prend place au sein des différents évidements du canal 33 intérieur du piston 3 évoqués ci-dessus.

Thus, here again, the modifications brought by the present improvement are at the level of the two pistons of the precompression dosing pump of the prior art. We list below the overall list with reference to Figures 9 and 10 of details:

• 1 / the differential piston 4 comprises for example the same bore 63 as that of the first embodiment mentioned here. In other words, it is a small of the cylindrical creating a communication between the interior of the skirt 42 and the surface of the shoulder 44. A local notch of the end-of-travel recess 45 carried internally by the skirt 42 is also provided so that the spring 5 does not close this communication;
• 2 / not only the base of the piston 3 is this time hollowed out, but also the parbe of the channel 33 inside the hollow rod 31 which is located upstream of the valve seat 32. It follows a space 35 of a slightly more complex shape. For example, the inner channel 33 of the piston 3 now widens twice (if we consider in the opposite direction of the flow of the product). The first enlargement is none other than the valve seat 32 of the prior art pump. A second enlargement 37 is now added thereto. It is situated approximately halfway between the seat 32 and the base of the piston 3.
  As regards the sealing lips of the piston 3 which isolate the pump chamber 23 at the level of the pump body 2, only the lip 34 oriented towards the chamber 23 remains as in the first embodiment studied above. The upper lip existing in the unimproved pump is still rather replaced by guide fins 36.
• 3 / a ring 60 is, in this second embodiment of the present improvement, disposed against the shoulder 44 of the differential piston 4 to act as a non-return valve. It is integral with a sleeve 66 surrounding the valve stem 41 which takes place within the various recesses of the channel 33 inside the piston 3 mentioned above.

In the context of this improvement, it is fundamental that, in particular when the pump is at rest, the sleeve 66 of the ring 60 is compressed axially against the shoulder 44 of the piston 4. This is obtained here by extending the sleeve 66 practically up to 'at the top of the rod 41 so that its open end is able to bear against the valve seat 32. In truth, the height of the sleeve 66 is somewhat greater than the axial distance then separating the shoulder 44 of the differential piston 4 and the valve seat 32. Also the abutment of the sleeve 66 on the seat 32 is accompanied by a slight buckling. In order to better control it despite variations in the sizes of the molded parts (tolerance of the order of 1/10 of a millimeter), the sleeve 66 does not have a constant diameter. Weaker at its open end, it has a widening 67 approximately halfway up (that is to say opposite the widening 37 of the channel 33 inside the piston 3). Inside the enlarged section are advantageously two annular reliefs 62. The rod 41 is for its part provided with two comparable annular reliefs 61. One takes place for example between the widening 67 of the sleeve 66 and a first relief 62 while the other is located between the two reliefs 62 of the sleeve 66. An axial clearance is also maintained between complementary reliefs. In this way, the buckling occurs only by bloating of the enlarged section of the sleeve 66, which eliminates any risk of deformation of another nature. Thus the ring 60 is in turn forcibly deformed similarly to the joint of the first embodiment.

Indeed, it rests both on a small surface 65 surrounding the rod 41 and on a cord 64 of circular support whose center is on the axis of the rod 41 and which is formed beyond the bore 63. However, the cord 64 protrudes over the shoulder 44 at one level higher than the surface 65. The ring 60 which is pressed by means of its sleeve 66 against the latter, therefore tends to warp. And, as in the first embodiment of the present improvement, a concave shape is thus maintained, the ring 60 folding down somewhat towards the valve rod 41. By reaction, the ring 60, which has a certain rigidity, is then applied sufficiently to the support cord 64 to guarantee the tightness of the corresponding contact. A fortiori, the contact at the surface 65 is then sealed so that any communication between the reservoir and the pump chamber 23 by the bore 63 is thereby completely broken.

In achieving this characteristic, the free end of the sleeve 66 advantageously comprises one or more slots 68 so as not to hinder the flow of the product when it is emitted through the channel 33. It is preferably cut in a bevel so that the piston 3 always remains centered around the sleeve 66.

This deformation characteristic imposed beforehand on the element 60 for closing off the bore 63 also ensures this second embodiment of the present improvement a theoretically perfectly reproducible operation. When the user pushes the hollow rod 31 of the piston 3 in order to actuate this pump, it first of all drives the differential piston 4 in the downward movement, the valve rod 41 of the latter resting against the seat 32 valve. During this short transient phase, the ring 60 remains pressed against the shoulder 44 since the relative position of the two pistons 3 and 4 is identical to that achieved, the pump being at rest. In this way, the pump chamber 23 is completely isolated from the outside and from the reservoir exactly as in the unperfected pump. At the same time, the pump chamber 23 decreasing in volume, the pressure of the product which it contains increases and eventually reaches the precompression value capable of causing withdrawal of the differential piston 4 relative to the piston 3.

We then find ourselves in the conditions of emission of the product illustrated in FIG. 9. In other words, the valve stem 41 is now detached from the valve seat 32 while the pressure of the product is applied to the shoulder 44 of the differential piston 4. However, it no longer applies directly to it. It is in fact exerted on the ring 60. If this does not change anything in terms of the operation of the differential piston 4, it also follows good retention of the ring 60 against the shoulder 44. As a result, the sleeve 66 can, while remaining in place on the rod 41, move away from the seat 32 and deliver passage to the product according to the double arrows shown in FIG. 9.

When the differential piston 4 finally comes into abutment against the hollow cylinder 24 of the pump body 2 at its end-of-travel step 45, the volume of pump chamber 23 stops decreasing. The pressure of the product therefore does not take long to drop so that the differential piston 4 returns to apply at its rod 41 against the valve seat 32. Consequently, the sleeve 66 is again compressed by this seat 32 which, consequently, takes over from the pressure of the product.

It is then that the user generally releases his force on the rod 31 of the piston 3. And immediately, the spring 5 causes the simultaneous ascent of the two pistons well applied to each other at the valve seat 32. The sleeve 66 remains meanwhile compressed axially between this seat 32 and the shoulder 44. The pump chamber 23 increases at the same time in volume and, as it remains at first isolated like what happens in the pump not perfected, a depression develops there. In other words, the pressure of the product is now on the side of the ring facing the reservoir. Also, as soon as the vacuum in the chamber 23 becomes sufficient to allow this pressure (which is none other than that prevailing in the reservoir) to overcome the force of application of the ring 60 on the bead 64 of support, the ring 60 lifts. As shown in FIG. 10, the ring 60 then tends to fall back towards its sleeve 66 while remaining firmly applied against the surface 65 of the shoulder 44 at the root of the rod 41. The product contained in the reservoir s 'therefore introduced into the pump chamber 23, sucked in by the vacuum which prevails there according to the double arrows shown in Figure 10. This intake mechanism continues as long as the pistons 3 and 4 go up into the pump body 2 .

When finally, the pump comprising this second embodiment finds itself at rest, the pressures exerted on either side of the ring 60 by the product become equal. Nothing therefore stands in the way of the return of the ring 60 against the cord 64, this position corresponding to the minimum deformation that the ring can undergo. From now on, the pump is ready for a new actuation which will take place exactly like that described in the previous pages, without any hazard occurring. Even, in the event of aging of the pump provided with this second embodiment of the present improvement, acceptable operation of the non-return valve formed by the bore 63 and its sealing ring 60 can indeed be guaranteed. A creep of the ring 60 is then certainly to be expected so that its application force on the support cord 64 decreases over time. However, there will always be a tendency to apply which will be sufficient to ensure the closure of the valve in question when the pistons descend. Thereafter, it is the very pressure of the product contained in the pump chamber which will take over to reinforce this closure.

Compared to the examples which have just been described in detail, the present improvement may possibly provide for the existence of several bores 63. Their number however remains limited to three at most. Indeed, the differential piston 4 is a molded plastic part. The multiplication of the bores 63 would weaken it because of the lower quality of the plastic flow junctions during filling of the mold. As regards the seal or the ring 60, it is also possible to mold them since it is not necessary to respect an extremely precise adjustment dimension with the valve rod 41. Finally, note that the precompression metering pump thus improved can be mounted on a tank not only at atmospheric pressure as has been assumed so far, but also slightly under pressure (for example up to 1.5 bars).

It also finds it advantageous to be mounted on a tank with a slight depression. This is particularly the case when it is associated with a vacuum tank, the walls of which deform as it is emptied without, however, adapting perfectly to the reduction in volume of the container as a result of a certain mechanical resistance. For this, however, the dosing pump should be designed slightly differently from that described above. Figure 11 shows how it might look.

This is how the difference is located at the fitting of the skirt 42 of the differential piston 4 around the hollow cylinder 24. From now on, it is carried out continuously, including therefore when the pump is in the rest position which is shown. It suffices for this that the respective lengths of the skirt 42 and of the cylinder 24 are chosen accordingly. And isolation of the pump chamber 23 from the reservoir results in this rest position.

This aspect is particularly interesting when the product must not be placed in the presence of air, otherwise it will lose its properties (by contamination or by oxidation). It protects the product in the tank from any contact with the air which has entered the pump chamber 23 as a result of leaks at the level of the sealing lip 34 of the piston 3.

Claims (15)

1.- Improvement improving the efficiency of a precompression dosing pump, said dosing pump making it possible to issue a product under pressure thanks to the collaboration of five cylindrical parts with a common axis: - a hollow tower (1), - a hollow body (2) having two open ends, said spinner (1) being fixed to a first end (21) of said hollow body (2) while a hollow cylinder (24) having an open section internally extends a second end (22) of said hollow body (2), - A first piston (3) mounted to slide in leaktight manner inside said hollow body (2) between a first and a second position, said first piston (3) coming to bear against said spinner (1) in said first position, a hollow rod (31) extending said first piston (3) towards said first end (21) of said hollow body (2) and internally comprising a valve seat (32), - a differential piston (4) slidingly mounted inside said hollow body (2) and comprising a shoulder (44) on the side of said first end (21) of said hollow body (2), said differential piston (4) extending towards said first end (21) of said hollow body (2) by a valve rod (41) engaging in said hollow rod (31) of said first piston (3) to collaborate with said valve seat (32), said piston differential extending towards said second end (22) of said hollow body (2) by a skirt (42) having an outer guide surface and an inner surface provided with a recess (45) as well as a lip (43) d sealing, said sealing lip (43) fitting around said hollow cylinder (24) at least as soon as said first piston (3) leaves said first position, said second position of said first piston (3) being reached when said section said hollow cylinder (24) opens abutment against said recess (45) of said inner surface of said skirt (42), - a return spring (5) disposed between said differential piston (4) and said end probe (22) of said hollow body (2), said differential piston (4) further comprising at least one bore (63) extending from said inner surface of said skirt (42) and opening onto said shoulder (44), a cylindrical closure element (60) threaded around said rod (41) of valve adapted to be applied against said shoulder (44) at two annular contacts between which opens said bore (63) so as to form a non-return valve to the mouth of said bore (63) and a free space (35) being formed around said shoulder (44) so that said closure element (60) can come off from said shoulder (44), CHARACTERIZED IN THAT, in particular when said dosing pump is at rest, said closure element (60) is kept deformed so that it is applied to said shoulder (44) with sufficient force to guarantee the tightness of said two annular contacts. 2. Improvement according to claim 1, characterized in that a first of said two annular contacts between said closure element (60) and said shoulder (44) is formed on a bead (64) projecting from said shoulder (44) between said bore (63) and said outer surface of said skirt (42), a second of said two annular contacts being formed on a surface (65) of said shoulder (44) located in the immediate vicinity of said rod (41) of valve and recessed with respect to said support cord (64), said first contact being broken when opening said non-return valve at the mouth of said bore (63) while said second contact is permanently maintained, said free space (35) provided around said shoulder (44) being adapted to allow the folding of said closure element (60) towards said valve rod (41) while said first contact is broken. 3. Improvement according to claim 2, characterized in that said closure element (60) is an elastomer seal having a central hole and an outer periphery; and in that, in particular when said metering pump is at rest, said closure element (60) is kept deformed by: a / said valve stem (41), said central hole of said seal having a diameter less than that of said valve stem (41) so that threading of said seal on said valve stem (41) causes warping of said seal ; b / a relief (61) of said valve stem (41) located at such a distance from said shoulder (44) of said differential piston (4) that once threaded around said valve stem (41), said seal is maintained by wedging at said central hole between said relief (61) and said shoulder (44). 4. Improvement according to claim 3, characterized in that said free space (35) formed around said shoulder (44) is constituted by an annular recess of said first piston (3). 5. Improvement according to claim 2, characterized in that said closure element (60) is a plastic ring having a central hole extended on one side by a hollow cylindrical sleeve (66) which is adapted to be threaded around said valve stem (41) and has an open end; and in that, in particular when said metering pump is at rest, said valve seat (32) of said first piston (3) is applied to said open end and axially presses said sleeve (66) against said surface (65) of said shoulder (44) in the immediate vicinity of said valve stem (41). 6. Improvement according to claim 5, characterized in that said open end of said sleeve (66) comprises at least one notch (68) so that the presence of said sleeve (66) does not hinder the passage of said product during its emission . 7. Improvement according to claim 5 or claim 6, characterized in that said open end of said sleeve (66) is bevelled so that there is automatic centering of said first piston (3) on said sleeve (66). 8.- Improvement according to any one of claims 5 to 7, characterized in that said cylindrical sleeve (66) comprises approximately at mid-height an enlargement (67) rapidly passing the diameter of said open end to that of '' an enlarged section, at least two annular reliefs (62) being formed inside said enlarged section between which takes place, with an axial clearance compatible with the tolerance of the parts, an annular relief (61) carried by said rod (41 ) valve so that said sleeve (66) deforms by buckling rather by bloating at said enlarged section. 9. Improvement according to claim 8, characterized in that said free space (35) formed around said shoulder (44) is constituted by a cylindrical recess having for axis of revolution said common axis of said parts of said metering pump, said recess extending from said valve seat (32) and having a widening (37) at said widening (67) of said sleeve (66). 10. Improvement according to any one of the preceding claims, characterized in that said bore (63) is a cylindrical channel with an axis parallel to said common axis of said parts of said precompression metering pump. 11. Improvement according to any one of the preceding claims, characterized in that said recess (45) of said inner surface of said skirt (42) is notched so as to release the start of said bore (63). 12.- Improvement according to any one of the preceding claims, characterized in that there are two or three bores (63) in said differential piston (4) and in that they are molded with said differential piston (4) . 13. Improvement according to any one of the preceding claims, characterized in that said first piston (3) slides in leaktight manner inside said hollow body (2) thanks to a single lip (34) oriented peripheral sealing. towards the pump chamber (23). 1 4.- Improvement according to any one of the preceding claims, characterized in that said closure element (60) is produced by molding. 15.- Improvement according to any one of the preceding claims, said metering pump being used in association with a vacuum tank, characterized in that the respective lengths of said hollow cylinder (24) and of said skirt (42) of said piston ( 4) differential are such that said sealing lip (43) always remains fitted around said hollow cylinder (24) even when said first piston (3) is in said first position, the communication with the pump chamber (23) being therefore possible only by said at least one bore (63) formed in said differential piston (4).

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