Fluid dispenser pump

#The present invention relates to a manually-actuated fluid dispenser pump, and to a fluid dispenser device including such a pump.

#In known manner, a fluid dispenser pump generally includes a pump body in which a piston is mounted to slide between a rest position and a dispensing position. The pump body is cylindrical and the end positions of the piston, namely the rest position and the dispensing position, are defined by various means, e.g. abutment means. When the pump is actuated, the pump chamber is filled with fluid, and the leaktightness constraints for the piston while it is moving inside the pump body are very stringent to avoid any risk of leakage. Therefore, the pump must exert non-negligible radial stresses on the piston while it is moving towards its dispensing position. Unfortunately, most pumps are used at irregular intervals, and the pump spends most of its time in the rest position. The high radial stresses that are exerted on the piston, also when it is in the rest position, can be disadvantageous in that ultimately they can damage the sealing lips of the piston or can deform them, thereby diminishing their leaktightness, which can cause the pump to malfunction. Furthermore, certain pumps use a second piston that is also mounted to move in the pump body between a respective rest position and a respective dispensing position. The second piston is generally mounted to slide in a small-diameter portion of the pump body. In that type of pump, the second piston forms or is connected in some way to the inlet valve and/or the outlet valve of pump chamber. Similarly to what is described above, the pump body is cylindrical and the second piston is mounted to slide in leaktight manner in said cylindrical portion of the pump body between its rest position and its dispensing position. For the second piston, there is a risk that, when it returns from its dispensing position to its rest position, i.e. generally during the stage in which the fluid contained in the pump chamber is expelled, the suction generated by said expulsion inside the pump chamber might cause the inlet valve of the pump to open early, or might cause the outlet valve of the pump chamber to close early, when valve opening and closure is controlled by said second piston. To solve that problem, it is possible to make provision to increase the radial stresses exerted by the pump body on the second piston. However, that requires a larger actuating force to actuate the pump. Such malfunctioning of the valves of the pump chamber can result in non-uniform quantities or “doses” of fluid being dispensed because the times at which said valves open and close are no longer accurately predeterminable and reproducible each time the pump is actuated.

#An object of the present invention is to provide a manually-actuated fluid dispenser pump that does not suffer from the above-mentioned drawbacks.

#Other characteristics and advantages of the present invention appear more clearly on reading the following detailed description given with reference to the accompanying drawings which are given by way of non-limiting example, and in which:

#FIG. 1 is a diagrammatic section view of a pump in an advantageous embodiment of the present invention;

#FIG. 2 is a detail view on an enlarged scale of a pump in a first variant embodiment of the present invention;

#FIG. 1 shows a pump including a pump body 10 in which a first piston 50 and a second piston 55 are mounted to slide between respective rest and dispensing positions. The present invention is described below with reference to this particular pump, but it is to be understood that the invention is not limited to the pump shown in FIG. 1. On the contrary, the present invention is applicable to any fluid dispenser pump in which at least one piston is mounted to slide in a pump body. More precisely, although in the pump of FIG. 1, the present invention incorporates two distinct pump body portions with two pistons, each of which implements the present invention, it is quite possible to apply the present invention to pumps having one piston only, or having two pistons but in which only one of said pistons is mounted to slide in a pump body incorporating the present invention.

#The pump shown in FIG. 1 thus includes a pump body 10 provided with a first pump body portion 11 in which a first piston 50 is mounted to slide, and with a second pump body portion 12 in which a second piston 55 is mounted to slide. The second pump body portion 12 may have an inside diameter that is small relative to the inside diameter of the first pump body portion 11. Therefore, the second piston 55 may have an outside diameter that is small relative to the outside diameter of the first piston 50. A pump chamber 20 is defined between said pistons 50 and 55, said pump chamber being provided with an inlet valve 30 and with an outlet valve 40. The first piston 50 may advantageously be associated integrally with a preferably hollow actuating rod 60 incorporating an expulsion channel 61 for expelling the fluid. A return spring 70 is generally disposed in the pump body 10, and it advantageously cooperates with the second piston 55 to return the pump automatically to its rest position after each occasion on which it is actuated. A ferrule 80 may be fitted into the top edge of the pump body 10 to define the rest position for the first piston 50, and a dip tube 90 may be assembled to the opposite edge of the pump body 10 so as to extend towards the bottom of a reservoir (not shown). The pump of FIG. 1 may be assembled to a reservoir (not shown) by means of a fixing ring 1 which may be of any type, and in particular screw-fastenable, snap-fastenable, or crimpable. Generally, a sealing gasket 5 is interposed between said fixing ring 1 and the neck of the reservoir (not shown).

#In the present invention, at least a portion of the pump body is organized to be frustoconical at least in part, so as to modify the radial stresses exerted by said pump body 10 on said first piston 50 and/or on said second piston 55.