US3502035A - Piston pump for dispensing liquids or fluid pastes - Google Patents

Description

March 24, 1970 R. FEDlT ETAL 3,502,035

PISTQN PUMP FOR DISPENSING LIQUIDS 0R FLUID PASTES 4 Sheets-Sheet 2 Filed Oct. 10. 1967 March 24, 1970 F m-r ETAL PISTON PUMP FOR DISPENSING LIQUIDS OR FLUID PASTES Filed Oct. 10. 1967 4 Sheets-Sheet 4.

United States Patent 3,502,035 PISTON PUMP FOR DISPENSING LIQUIDS OR FLUID PASTES Ren Fedit, Paris, and Marcel Janodet, Fresnes, France, assignors to Vaporisateurs Marcel Franck S.A., Paris, France, a French society Filed Oct. 10, 1967, Ser. No. 674,216 Claims priority, application France, Oct. 12, 1966,

79,737 rm. (:1. F04b 21/08, 43/00 US. Cl. 103178 13 Claims ABSTRACT OF THE DISCLOSURE This invention relates to pumps for delivering liquids or fluid pastes to be dispensed.

These pumps include a piston adapted to reciprocate in a cylindrical part of a pumping chamber, and a delivery conduit which leads to an ejection orifice. The inlet opening of this delivery conduit is located on the periphcry of the piston, so that this opening remains blocked oif by the inner face of the cylindrical part of the pumping chamber in the rest position and at least at the beginning of the compression stroke of the piston in this chamber; the chamber is arranged in such a manner that it clears the inlet opening when the piston has completed the initial part of its compression stroke.

The invention is concerned more particularly, but not exclusively, with pumps of this type which are incorporated on a container having a stopper which acts as a support for the pump, and which is surmounted by a plunger rigid with the tubular rod of the piston. The piston acts as the delivery conduit between the pumping chamber and a delivery nozzle, in particular an atomizing nozzle, located on the periphery of the plunger. The piston and its control plunger are continuously urged towards the upper rest position by a return spring.

Such atomizers, dispeners and pumps have certain advantages.

For example, they are rigorously water (liquid) tight when lying in any position, and they are of simple construction and relatively cheap.

Furthermore, the dispensing cannot take place unless the delivery pressure is sufficiently high to assure a good jet without dribbling at the nozzle, or in the case of atomization, a suitable dispersion of the atomized liquid in the surrounding air.

Nevetheless, atomizers, dispensers and pumps of the type in question have a serious disadvantage.

If the pumping chamber has been completely filled with a practically incompressible liquid or paste, and if the inlet valve is closed, the piston cannot effect the initial part of its compression stroke which, however, is necessary for the liquid or paste to be able to escape from this chamber through the delivery conduit of the pump.

To remedy this disadvantage, according to the present invention, at least a part of the pumping chamber, in particular the part which is located beyond the part through which the piston travels, is arranged, by its geometric shape and/or by a reduction of its thickness and/ or by an appropriate choice of the material of which it is made, so that this part can, under the effect of increasing inner pressure, be deformed elastically thus increasing the capacity.

According to a first embodiment of the invention, the walls of the deformable part of the pumping chamber are made extensible by making them of an elastomer.

According to another embodiment of the invention, the walls of the pumping chamber are made flexible and this chamber is given a geometric shape such that it can, under the effect of the inner pressure, elastically increase the capacity without appreciably increasing its surface area.

When the pump draws in a liquid or a fluid paste through a tube, in particular through an immersed tube of plastic material, according to another embodiment of the invention, this tube, which is connected to the pumping chamber, is arranged to at least participate in the elastic variations of capacity of the pumping chamber, by displacing the inlet valve of the pumping chamber from between the chamber and the tube towards the upstream of the tube, preferably all the way to the inlet end of the tube.

This tube, which extends between the inlet valve and the pumping chamber, is preferably flattened.

Other characteristics and advantages of the invention will become apparent from the following description, given merely by way of example, and the accompanying drawings.

FIGURES l and 2 show, partially in axial section and partially in elevation, a part of a liquid atomizer arranged according to the invention, respectively in the rest position and during the delivery stroke of the piston in the pump.

FIGURES 3, 4 and 5 show, in analogous views, three other embodiments of atomizers according to the invention;

FIGURE 6 shows, in axial, section, a piston of an atomizer pump, this piston being constructed according to another modification of the invention.

FIGURES 7 and 8 show, partially in elevation and partially in axial section, parts of liquid atomizer containers or fluid paste distributors constructed according to two other modifications according to the invention.

FIGURE 9 shows, partially in elevation and partially in axial section, a liquid atomizer container or a fluid paste distributor constructed according to still another modification of the invention.

FIGURE 10 is a section along the lien XX of FIG- URE 9.

FIGURE 11 shows the same section as FIGURE 10 but in a different stage of operation.

FIGURES 12 and 13 show in axial section a part of a pumping chamber constructed according to another modification of the invention.

The liquid atomizer, or fluid paste distributor, shown in FIGURES l and 2, comprises, incorporated in a container 1, a pump adapted to draw in and deliver the liquid or fluid paste. This pump has a piston 5 adapted to reciprocate in a cylindrical part 6 of a pumping chamher, and a delivery conduit 4 which leads to a dispensing nozzle 2, in particular an atomizing nozzle. An immersed tube 13 connects the pumping chamber to the inside of container .1. The inlet opening 3 of this delivery conduit 4 is located on the periphery of the piston 5, in the present case in a peripheral groove 21 of the piston 5, so that the opening 3 and the groove 21 remain blocked off by the inner face of the cylindrical part 6 of the pumping chamber, in the rest position and at least at the beginning of the compression stroke of the piston 5 in this chamber. The pumping chamber is provided with means adapted to clear the opening 3 and the groove 21 when the piston 5 has completed the initial part of its compression stroke, these means being for example in the form of a peripheral shoulder 9 at the beginning of an enlarged portion of the pumping chamber.

The container 1 is closed by a stopper 14 to which the pump is rigidly connected. The pump is surmounted by a plunger 10 which, in turn, is rigidly connected to the tubular rod 17 of the piston 5, in which the delivery conduit 4 is located.

A return spring 11, inserted between the stopper 14 and the plunger 10, continuously urges the plunger 10 and the piston 5 towards the top, i.e. towards the rest position shown in FIGURE 1.

With the construction that has so far been described, after a suction stroke of the pump, when the pumping chamber is completely full of liquid or of fluid paste drawn up from the container 1, and the inlet valve 12 is closed, the piston 5 could not descend in the cylinder 6 to clear the inlet opening 3 by passing the shoulder 9, and consequently the pump would remain blocked.

To remedy this disadvantage, according to the invention, at least a part of the pumping chamber, in particular the part which is located beyond the cylinder 6 through which the piston 5 travels, is arranged in a manner such that it can, under the elfect of increasing inner pressure, be deformed elastically, thus increasing the capacity in order to be able to receive the liquid or the paste (practically incompressible) displaced by the piston 5 from the cylinder 6 as the piston begins its compression stroke.

This result can be obtained in particular by an appropriate reduction of the thickness of the wall of this part of the pumping chamber and/or by the nature of the material constituting this part.

In the embodiment shown in FIGURES l and 2, the cylinder 6, and the compression chamber 7 located towards the bottom 8 of this cylinder, are constructed together with the bottom 8 in a single piece of elastically deformable plastic material, for example, by injection moulding.

The peripheral wall of the part 7 of the pumping chamber is made more easily deformable by making this part 7 thinner, which results in the increase of the inner crosssection of this chamber, beyond the peripheral shoulder 9, whose position determines the length of the compression stroke of the piston 5, and consequently the pressure which the liquid to be atomized reaches before being delivered into the conduit 4.

The atomizer operates in the following manner.

It will be assumed that the chamber 6-7 is full of liquid to be atomized previously drawn in by the pump, and that the pump is in its rest position shown in FIG- URE 1.

When the plunger 10 is pushed downwards against the action of its return spring 11, the piston 5 drives the liquid into the part 7 of the pumping chamber.

Since the inlet valve 12 is closed, the liquid cannot escape from the compression chamber, which it dilates, as shown in FIGURE 2.

The pressure of the liquid, which continues to expand the chamber 7, increases until the moment when the inlet 3 of the delivery conduit 4 passes the shoulder 9, which permits the liquid in the chamber 7 to escape via the delivery conduit 4 through the atomizing nozzle 2 to the outside. 7

Thus there is the possibility of having the liquid arrive at the atomizing nozzle 2 only when the pressure is sufiicient to assure fine atomization.

As the liquid escapes from the compression chamber 7, this chamber returns elastically to its initial shape shown in FIGURE 1.

When the plunger 10 is released, the spring 11 moves the piston 5 back up again in the cylinder 6 of the pump which, as long as the conduit 4 still communicates with the chamber 7, draws back into this chamber the liquid which remains at the edge of the nozzle 2 and in the conduit 4, which hinders any dribbling by the nozzle or delivery tube 2.

This return of the liquid from the delivery conduit into the chamber 7 is promoted, on the one hand, by the absence of any delivery valve, and on the other hand, by gravity. Thus the liquid in the container, which has to move upwards against gravity in the immersed tube 13 and pass through the valve 12, is only drawn in a positive fashion when the inlet 3 of the delivery conduit is once again blocked off by the cylinder 6.

When the plunger 10 has come back to its initial position shown in FIGURE 1, a new atomization can be obtained by pushing this plunger downwards again as before.

It can be advantageous to construct the cylinder 6 in a single piece together with the stopper 14, which can be fixed on the neck of the container 1, for example, by threads 15.

In its upper part, that is to say near its inlet, the cylinder 6 is provided with a hole 16 passing through the wall of this cylinder. This hole 16 is blocked off by the piston 5 as long as the piston remains in its upper rest position shown in FIGURE 1, towards which it is urged by its return spring 11, and the piston 5 clears the hole 16 at the beginning of the compression stroke.

When the piston 5 clears the hole 16, as shown in FIGURE 2, the surrounding air can penetrate between the plunger 10 and the stopper 14, then between the rod 17 of the piston and the cylinder 6 through the hole 16 in the container 1 in order to replace the volume of liquid removed.

In the embodiment of FIGURE 3 the elements analogous to those FIGURES 1 and 2 are designated by the same reference numerals, followed by the letter a.

The embodiment shown in FIGURE 3 differs from that shown in FIGURES l and 2 essentially by the fact that the return spring 11a of the piston 5a is disposed as a compression spring between the head of the piston 5a and a peripheral shoulder 18a at the bottom 8a of the cylinder, and by the fact that the cylinder 6a of plastic material is crimped in a metal capsule 19, which is itself crimped on the neck of the container 1a.

The operation of this embodiment is similar to that which hase been described with reference to FIGURES 1 and 2.

Nevertheless, the mounting of the compression spring 11a inside the cylinder 6a of deformable material, tends to elongate this cylinder and to urge it against the piston 5a, which permits the walls of the cylinder to compensate for the play which is formed between the piston and the cylinder by wear of the walls during operation, and permits a plastic material to be used which is flexible but of low elasticity.

According to another embodiment shown in FIGURE 4, the cylinder, including its compression chamber, is given a uniform cross-section along its entire length. In the embodiment of FIGURE 4 the elements analogous to those of FIGURES 1 and 2 or FIGURE 3 are designated by the same reference numerals, followed by the letter b.

During the compression stroke shown in FIGURE 4, the cylindrical part 6b located near the bottom 8b begins to dilate under the pressure of the liquid until the moment when this wall uncovers the inlet 3b of the delivery conduit 4b, which permits the liquid to escape through the atomization nozzle (not shown).

It can be advantageous to render the upper part of the cylinder 6b more rigid, which can be done either by increasing the thickness of its wall or by surrounding this wall by constraining means, which can be, for example, metal.

The collar 25b provided on the cylinder 6b can serve as a seal acting on the neck of the container 1b, and this collar comprises for this purpose three circular concentric ribs 26.

According to still another embodiment of the invention as shown in FIG. 5, several successive atomizations can be obtained during a single compression stroke of the piston 5c in the cylinder. In the embodiment of FIGURE 5 the elements analogous to those of FIGURES 1 and 2 or FIGURE 3 are designated by the same reference numerals, followed by the letter c.

For this purpose, several depressions are provided on the inner face of the cylinder 60, these depressions increasing the cross-setcion of the cylinder beyond that occupied by the piston. During the progression of the piston in the cylinder, :1 part of the liquid displaced by the piston passes successively around the front part of the piston to penetrate into the inlet of the delivery condu1t4c.

In the embodiment represented in FIGURE 5, two successive grooves 19 and are provided in the inner face of the cylinder 60, one behind the other, in the axial direction of this cylinder.

In this case, it is appropriate to locate the inlet of the delivery conduit in a peripheral groove 210 of the piston 50.

It can be seen that, during the compression stroke, the liquid displaced by the piston in the cylinder is first of all put under pressure, for it can only reach the groove 21c when this groove arrives at the upper end of the groove 19 through which the liquid can then flow from the cylinder 6c to the delivery conduit 40, by passing around the front part of the piston 5c.

When, on continuing to descend in the cylinder 60, the piston 50 advances beyond the groove 19, the rest of the liquid, which is located in the bottom of the cylinder, 1s again put under pressure until the groove 21c reaches the upper end of the following groove 20, which permits the liquid, as before, to escape through the groove 20, by passing around the front part of the piston 50, into the delivery conduit 40, which results in a second atomization of liquid by the same stroke of the piston 5c in tht= cylinder 6c.

Needless to say, instead of providing two rectilinear grooves 19 and 20, formed in the inner face of the cylinder. 60, three or more grooves can be provided, which means that three or more successive atomizations are obtained during a single stroke effected by the piston in the pump.

The groove 19 can of course be completed by other similar grooves, distributed on the periphery of the cylinder 6 at the same height as the groove 19, and the same can be done for the groove 20, as shown in FIG- URE 5.

According to still another feature, also shown in FIG- URE 5, and which in certain cases can be used alone, on the one hand, the skirt of the cylinder 60 is connected to an opening 23 of smaller diameter by a conical bore 22, in which opens the air channel Me which communicates with the inside of the container 1c, and on the other hand, the rod 170 is connected to the piston 50 by a cone 24 which is complementary to the bore 22.

Thus, when the piston 5c is located in its rest position shown in FIGURE 5, the cone 24 blocks off the conduit 16c thereby cutting the communication between the inside of the container and the outside, so that no liquid can escape from the container if the container is tipped over.

When the plunger 10c is depressed, the cone 24 moves away from the conduit 16c which is thus immediately, from the beginning of the stroke of the piston 5c in the cylinder 6c, put into communication with the outside through the opening 23.

It will be noted that, in the rest position, all the embodiments described assure excellent liquid tightness between the cylinder of the pump and the delivery conduit, due to the fact that the walls of the cylinder block off the inlet of this delivery conduit.

The different pump pistons shown in the drawings can be made either of plastic material or of metal.

If the piston and cylinder are made of plastic material, a hard plastic material such as a polymer resin of formaldehyde (sold by Du Pont de Nemours under the name Delrin) is advantageously chosen for the piston, and for the cylinder a deformable plastic material whose Shore hardness is about 0 to 95, such as the polymer of polyvinyl chloride sold under the commercial name Lucolene or the copolymer of vinyl ethylene acetate sold under the commercial name of Ultra-Thene.

By forming the piston of plastic material and by doing the same for the cylinder 6-7, the inlet valve 12 and the immersed tube 13, a pump can be constructed which can serve for the atomization of corrosive or unstable liquids, provided that the return spring 11 (which in this case is the only metal part of the combination), is mounted outside the pump, whereby this spring surrounds the rod 17 of the piston and bears, on the one hand, against the stopper 14, and on the other hand, against the plunger 10, as shown for example in FIG- URE 1.

In the modification of FIGURE 6 the elements analogous to those of FIGURE 1 are designated by the same reference numerals followed by the letter d, with the exception of the inlet valve which is identical to the valve 12a of FIGURE 3. According to the modification of FIGURE 6, a composite piston is used, having, on the one hand, a metal part which has, at the end of a tubular rod 17d forming the conduit 4d, a peripheral flange 27 in which the inlet 3d of the conduit 4d is located, and in the periphery of which is formed the annular groove 21d, and on the other hand, annular seals 28 and 29, for example of synthetic rubber, inserted on the rod 17d one on each side of the flange 27.

In the various atomizers shown in FIGURES 1, 3, 4 and 5, the increase of the capacity of the pumping chamber, which yields elastically under the increasing inner pressure, leads to an increase of the inner surface area of the pumping chamber which expands, resulting in a corresponding decrease of the thickness of the material constituting the wall of this chamber, this material being subjected to an elastic extension.

Such a deformation of the pumping wall exerts relatively large stresses on the material constituting this wall, and the pressures necessary for this deformation can be relatively high and are difficult to control.

Thus, according to another embodiment of the invention, a part of the pumping chamber, in particular a part which is located beyond the part through which the piston 5 travels, is given a geometric shape such that, under the increasing pressure of the contents displaced by the piston 5 during the initial part of its compression stroke, this part can increase in capacity by elastic deformation, without a corresponding increase of its surface area, or at least without an appreciable increase.

According to a first embodiment, shown in FIGURE 7 (in which the reference numerals are the same as in FIGURES 1 and 2 except for the valve 12a and the part 7g), the part 7g of the pumping chamber is given the form of a deformed, in particular flattened, cylinder of revolution, which, under the effect of the increasing pressure of its contents, can be deformed elastically in order to reach or to approach more closely the form of the non-deformed cylinder of revolution.

According to another embodiment shown in FIGURE 8 (in which the reference numerals are the same as in FIGURES l and 2 except for the valve 12a and the part 7h), the part 7h of the pumping chamber is shortened by annular folds 30, forming a sort of peripheral bellows, which permits the cylindrical part 7h of the pumping chamber to become elongated under the effect of the increasing pressure of its contents, while the folds 30 of the peripheral bellows become flattened.

According to a modification (not shown) the cylinder 7]: can be provided with longitudinal folds, instead of the peripheral folds 30 shown in FIGURE 8. The increase in capacity of the cylinder thus folded which, un-

der the effect of the inner pressure becomes unfolded, then results in an increase in the transverse section.

When the pump draws in the liquid or the fluid paste, in the embodiment shown in FIGURE 9 (in which the elements which have not been modified have the same reference numerals as in FIGURES 1 and 2), through an immersed tube 13 which ends near the bottom of the container 1, it can be advantageous to leave the elastic variations of the capacity of the pumping chamber up to this tube 13f, or at least to make the tube 13 participate in these variations of capacity.

For this purpose, the tube 13 is included in the pumping chamber by moving the inlet valve 12 from the pumping chamber upstream in this tube 13 in particular all the way to its lower end, as shown in FIGURE 9.

Furthermore, it is appropriate to flatten the tube 13 between its ends, one of which is connected to the valve 12 and the other to the part 7 of the pump. Thus, under the effect of the increasing pressure during the compression stroke of the piston 5 in the cylinder 6, the tube 13f can increase in capacity without an increase of its inner surface area, which permits the opening 3, 21 (see FIG- URES 1 and 2) to reach the shoulder 9 in the cylinder 6 against the effect of increasing pressure, which remains easily controllable, on the one hand by the degree of flattening of the tube 13 and on the other hand by the elastic flexibility of its wall, which permits the use in the pumping chamber of a part 7 which can even be made of rigid material.

FIGURE 10 shows the tube 13 in section before the compression stroke of the piston 5 in the cylinder 6.

FIGURE 11 shows the same tube 13 in an extreme position which it can, possibly, reach when the opening 3, 21 of the piston 5 reaches the shoulder 9 in the cylinder 6.

According to another modification, a part of the pumping chamber can be given the shape of a deformed sphere, in particular of a flattened sphere, shown at 31 in FIG- URE 12, whose walls, when the pressure increases, become deformed to finally reach the shape of the perfect sphere shown in FIGURE 13, or a shape which at least approaches this shape, thus increasing its capacity without an appreciable increase of its inner surface area.

Such a spherical part 31 of the pumping chamber can be formed by the part previously designated by 7 of this chamber or by a part of the tube 13a or again by a separate element inserted between the part 7 and the tube 13f, the inlet valve 12 being then mounted either at the lower end of the tube 13 or between this tube and the inlet opening of the spherical part 31.

The combination formed by the pump incorporated in the container can form an atomizer for liquid products such as perfume or pharmaceuticals, or paints, or liquid insecticides, or again to form a dispenser for fluid pastes such as sun creams, shaving creams, etc.

Although the invention has been described with reference to various particular embodiments, it should be understood that the invention is not limited thereto as various modifications could be made without departing from the spirit or scope of the invention.

What we claim is:

1. A pump adapted to be mounted on a container for pumping contents having liquid flow characteristics of the container comprising a pumping chamber including a cylindrical part having a cylinder wall, a piston mounted in said cylindrical part and adapted to reciprocate therein, a plunger operatively connected to said piston and adapted to be depressed to cause said piston to perform a compression stroke from a rest position, and spring means acting on the piston-plunger combination, and adapted to cause said piston to perform a suction stroke from said depressed position to said rest position, a delivery conduit provided in said piston, said delivery conduit leading to an ejection orifice and having an inlet opening located on the periphery of said piston, said inlet opening of said delivery conduit being blocked off by said cylinder wall in the rest position of said piston and during the initial part of said compression stroke, and said pumping chamber being adapted to clear said inlet opening when said piston has completed said initial part of said compression stroke, said pumping chamber including an elastically deformable part located beyond, in the direction of travel of said piston during said compression stroke, said cylindrical part, said pumping chamber including a one-way inlet valve located beyond, in the direction of travel of said piston during said compression stroke, said cylindrical part, said inlet valve being provided with inlet means adapted to be immersed in the contents of said container, said inlet valve being adapted to permit the intake therethrough of the contents of the container into said pumping chamber, said deformable part of said pumping chamber being adapted under increasing pressure in said deformable part caused by said compression stroke of said piston, to become elastically expanded to increase the capacity of said deformable part, said elastically deformable part returning by its elasticity to its original undeformed state as the inlet opening of the delivery conduit is cleared and the contents in the pumping chamber flow to said delivery conduit, said piston returning to its rest position following the compression stroke to draw fresh contents into the pumping chamber.

2. A pump according to claim 1 in which said elastically deformable part of the pumping chamber is at least partially defined by an elestically deformable wall, which is made of an elastomer and whose thickness is sufliciently small so that said deformable part can be expanded by the displacement of the contents of said pumping chamber by said piston during said compression stroke.

3. A pump according to claim 2 in which said cylindrical part of the pumping chamber is at least partially defined by an elastically deformable wall whose thickness decreases in the direction of travel of said piston during said compression stroke.

4. A pump according to claim 2 in which said cylindrical part of the pumping chamber is at least partially defined by a wall whose thickness is sufficiently great so that said cylindrical part cannot be expanded by the displacement of the contents of said pumping chamber by said piston during said compression stroke, and in which said cylindrical part is of smaller diameter than said deformable part when said deformable part is in its position of rest, whereby said cylindrical part blocks off said inlet opening of said delivery conduit and said deformable part clears said inlet opening.

5. A pump according to claim 1 in which said cylindrical part of the pumping chamber has, within the stroke of said piston, at least two grooves forming regions of greater cross-section than said cylindrical part, said grooves succeeding one another with a certain interval in the direction of travel of the piston, each said groove being adapted during said compression stroke, to clear said inlet opening of said delivery conduit and to provide communication between said inlet opening and a region of the pumping chamber ahead of said piston.

6. A pump according to claim 1 in which said elastically deformable part of said pumping chamber has a geometric form adapted to increase its capacity without appreciably increasing its surface area.

7. A pump according to claim 6 in which said elastically deformable part of said pumping chamber has the form of a distorted cylinder whose cylindrical wall is flattened, said distorted cylinder being adapted, under increasing pressure therein, to become deformed to tend to assume the form of an undistorted cylinder to increase the capacity of said deformable part.

8. A pump according to claim 6 in which said elastically deformable part of said pumping chamber has the form of a distorted sphere whose spherical wall is flattened, said distorted sphere being adapted, under increasing pressure therein, to become deformed to tend to assume the form of an undistorted sphere to increase the capacity of said deformable part.

9. A pump according to claim 6 in which said elastically deformable part of said pumping chamber has the form of a cylinder axially shortened by a distortion of its cylindrical wall to form an annular bellows, said bellows being adapted, under increasing pressure therein, to become elongated to increase the capacity of said deformable part.

10. A pump according to claim 1 in which said elastically deformable part of said pumping chamber comprises a tube made of elastic material and adapted to extend down to the neighbourhood of the bottom of the container, said inlet valve being mounted at the bottom end of said tube, said tube being adapted, under increasing pressure therein, to become deformed to increase the capacity of said deformable part.

11. A pump according to claim 10 in which said tube is flattened on at least a part of its length downstream of said inlet valve.

12. A pump according to claim 1 in which said pumping chamber is in the form of a cylinder having a very flexible wall, and in which said spring means comprises a compression spring mounted between said piston and the bottom of said cylinder, whereby said spring tends to elongate said cylinder thereby tending to urge said flexible cylinder wall against said piston.

13. A pump according to claim 1 in which said cylindrical part of said pumping chamber is extended, in the direction of the suction stroke of said piston, by a converging conical bore leading to an opening communication with the atmosphere, a ventilation channel being provided leading from the interior of the container and opening out on said conical bore, and in which said piston has a conical part complementary to said conical bore, said conical part being adapted to block off said ventilation channel in the rest position of said piston, and adapted to clear said ventilation channel to allow said ventilation channel to communicate with the atmosphere as soon as the compression stroke begins.

References Cited UNITED STATES PATENTS 3,044,413 7/1962 Corsette 92170 3,194,447 7/1965 Brown 222-321 FOREIGN PATENTS 1,201,684 9/1965 Germany.

1,011,494 4/1952 France. 1,459,735 10/1966 France.

HENRY F. RADUAZO, Primary Examiner US. Cl. X.R.

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