The present invention refers to spray pumps and, more particularly, it is related to spray pumps of the lost motion displacement piston type, useful for spraying liquids from containers therefor.
It is well known that pressurized spray containers have lost certain popularity because the health authorities of different countries have ascertained that the gaseous propellants used to spray the liquid contained therein, have the disadvantageous property of being air pollutants which affect the ozone content of the atmosphere, whereby their use has been restricted and presumably should be prevented as much as possible. Said health authorities have been encouraging, therefore, the use of other types of spraying devices, particularly those which do not use any gaseous high pressure propellant, whereby the research and development activities of many companies in the world have been foccused towards the development of this type of devices.
The different types of piston displacement pumps extant in the market and built in accordance with the prior art, however, suffer of a number of drawbacks, particularly in connection with the possibility of leakage of the liquid from the container when at rest and alos in view of the inefficiency of some check valves used in said devices, as well as the costly diaphragms which are generally provided to prevent leakage from the interior of the container when the pump is being actuated.
On the other hand, the means provided in many of the prior art piston type pumps for venting the container in order to prevent the creation of a vacuum as the liquid is being dispensed therefrom, generally comprise pinholes at suitable places, in order to permit the entrance of air from the atmosphere into the container, whereby this type of containers generally produce considerable leakage when carelessly left standing on their sides or upside down when not in use. On the other hand, the prior art piston displacement spray pumps are generally provided with a piston having a lost motion mounting on the stem of the pump in order to alternately obstruct and clear the exit conduit on each cycle, for producing mist and the like. This conduit, however, has been generally built interiorly of the stem, such as by providing an axial bore in the said stem, which is generally a one-piece member, whereby the problems of molding and constructing said stem having the very thin bore necessary to permit the flow of the liquid outwardly of the device, have been generally very complex and have left much to desire as regards the economy of production and the efficiency of the pumping action of this type of devices. Also, the check valves provided at the inner end of the pumping chamber or cylinder, have been generally valves which merely consist of a thickened end of the stem itself, which, when pressed, plugs a bore communicating the pumping chamber with a flexible pipe introduced in the liquid, or merely consist of a ball-type check valve, both of which are somewhat inefficient and tend to cause some pumping problems.