Abstract:
A dispensing device for fluid substances, including a pushbutton in which a chamber is provided housing a piston, the piston being loaded by an elastic mechanism to urge a front projecting appendix thereof into a dispensing hole for the substance, to hence sealedly close the hole, the pushbutton presenting a seat enabling a hollow stem to be coupled therethrough through which the pressurized substance is fed to the device. In the chamber there is housed an at least partially cylindrical member in an interior of which the piston slides, in the member there being provided at least one passageway opening to the front of the piston and communicating with a bore of the stem when the device is positioned on the pump.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a dispensing device for fluid substances. 
     More particularly it relates to a dispensing device for fluid substances both in the form of cream and in the form of less viscous products such as sprays, deodorants and the like. 
     2. Discussion of the Background 
     In the known art a pushbutton is fixed to a hollow stem projecting from a container. Channels connecting the stem bore to a product dispensing hole are provided in the pushbutton. When dispensing is required, pressurized fluid withdrawn from a container is fed into the stem bore. Downstream of the stem there can be provided either a conventional pump operated by pressing the pushbutton, or a valve which is normally closed but opens on pressing the pushbutton; in this latter case the vessel containing the substance to be dispensed must be under pressure. 
     This known art has the drawback that on termination of a dispensing operation, all the residual product in the stem and in the pushbutton conduits upstream of the dispensing hole is in contact with air; it can therefore dry out or deteriorate and block the pump or valve and hence prevent correct product dispensing on subsequent use. 
     To obviate these known problems devices have been conceived such as those described in EP0803294. That document describes a dispensing device comprising a dispensing pushbutton in which a piston is provided from which there projects a stem which when in the non-dispensing position closes the dispensing hole. In this manner the product contained in the stem and in the conduits provided within the pushbutton is isolated from the air, the device hence being not subject to malfunction deriving from incrustations which can form in said conduits. 
     However the aforesaid device (as in the case of many others present in the known art) presents considerable drawbacks. 
     It is extremely difficult to mould the pushbutton, usually of plastic, because considerable thickness changes are present in proximity to the joint between the chamber in which the piston slides and the cylindrical portion by which the pushbutton fits onto the stem. These thickness variations generate residual stresses in the moulding, leading to ovalization in that region in which the piston is housed and slides. 
     This creates considerable problems for the seal between the piston lip and that conduit surface along which the piston slides. 
     SUMMARY OF THE INVENTION 
     An object of the present invention is therefore to provide a dispensing device which represents an improvement over the known art, and which in particular overcomes the sealing problems present in the aforedescribed solutions. 
     A further object of the present invention is to provide a device of simpler construction which enables the piston to operate and slide in an optimal manner. 
     These and other objects are attained by a dispensing device for fluid substances formed in accordance with the technical teachings of the accompanying claims. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Further characteristics and advantages of the invention will be apparent from the description of a preferred but non-exclusive embodiment of the dispensing device for fluid substances illustrated by way of non-limiting example in the accompanying drawings, in which: 
         FIG. 1  is a section through a device of the present invention in a non-dispensing position; 
         FIG. 2  is a section through the device of  FIG. 1  in a dispensing position; 
         FIG. 3  is a section through an alternative embodiment of the device of the present invention in a non-dispensing position; and 
         FIG. 4  is a section through the device of  FIG. 3  in a dispensing position. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     With reference to said figures, these show a dispensing device indicated overall by the reference numeral  1 . 
     It comprises a pushbutton formed preferably of plastic material by moulding. A transverse chamber  3  presenting a frontal aperture  5  is provided in its interior. An annular seat  6  is provided on the end  4  of the chamber  3 , from which end there projects an abutment  7  the use of which is clarified hereinafter. In the end there is also provided an air passageway  8  communicating with the outside. 
     The pushbutton  2  comprises a seat  9 , in the wall of which there is an annular groove  10 . This seat  9  is arranged to receive and clamp by means of the groove a hollow stem  9   a  having a bore  9   b  (see  FIG. 1 ) through which the substance to be dispensed is fed to said device. This substance passes through the stem bore under pressure. Hence the stem can be either that of a conventional dispensed pump or that for operating a valve associated with a pressurized vessel of known type. A member  11  for closing the chamber  3  is fitted into the chamber  3 . The member  11  presents a cylindrical portion  11   a , preferably of circular cross-section, which fits onto the end of the chamber  3 , namely into the annular seat  6 . Interference is provided between the annular seat  6  and the cylindrical portion  11  a to ensure a perfect seal between the parts. Annular projections can be provided on the surfaces of the annular seat to improve the seal between the seat and the member  11 . 
     The member  11  also presents a widened front portion  11  b carrying at its end a dispensing hole  15  provided axially to the member  11 . A piston  12  movable against an elastic means (specifically a spring) is present within the cylindrical portion  11   a.    
     On its front part the piston  12  presents a first lip  13   a  arranged to seal against the cylindrical portion  11   a , and a rear second lip  13   b  having merely a guide function in the illustrated example. The piston also presents, projecting frontally from it, an appendix  16  for sealedly closing the hole  15  when inserted therein. Essentially the piston/appendix combination forms a valving element for the hole  15 . The spring  14  is specifically positioned between the piston  12  and the end of the chamber  3  in such a manner as to urge the appendix  16  into the hole  15 . 
     The member  11  presents a passageway  22  which connects the front part of the piston, from which the appendix  16  extends, to the stem bore when the device is positioned on it, hence enabling a pressurized fluid originating from the stem to flow between the front surface of the piston and the dispensing hole Operating the pushbutton causes the compartment  18  to fill. When the pressure in the compartment  18  is such as to overcome the resistance of the spring  14  the piston withdraws to its end-of-stroke position and the appendix  16  frees the hole  15  to hence enable the substance to be dispensed. The end-of-stroke position is shown in  FIG. 2 ; in it can be seen a projection  19  protruding from the rear end of the piston to rest against the end of the chamber  3  (specifically against the abutment  7 ) precisely to define this end-of-stroke position of the piston. Any air which may be present between the rear of the piston  12  and the end of the chamber  3  escapes through the air passageway  8  during withdrawal of the piston  12 . 
     It should be noted that the appendix  16  is set and maintained coaxial to the hole  15  by suitable ribs  20  visible in  FIG. 2  and cooperating with an outer surface  16   b  of the appendix  16 . In the present embodiment the ribs are three in number and are disposed 120° apart, but can be of any number and can assume any configuration. The appendix  16  also presents a seal portion  16   a  suitable to penetrate into the hole  15  to sealedly close it, and is connected to the guide surface  16   b  by a step  21  which acts as an abutment and a stop for the piston stroke when the pressure within the compartment  18  falls below that provided by the spring  14 , consequently the piston advancing to urge the appendix  16  in the hole  15  into the closure position. In this situation the fluid within the pushbutton  2  and in the stem interior is isolated from the external environment. 
     Advantageously the compartment  18  has a considerable volume and a passage cross-section much greater than that defined by the passageways  22  and by the stem bore. Consequently the fluid is able, during dispensing, to slow down considerably within this compartment  18 . This is very positive particularly when the fluid product to be dispensed is a cream or a foam. 
     In conclusion it should be noted that the member  11  presents on its surface an annular projection  23  preferably but not necessarily cooperating with a suitable groove  24  provided in the surface of the chamber  3  for sealedly fixing the member to the pushbutton  2  by interference. 
     The assembly of a device conceived in this manner is very simple. This is done by inserting the piston  12  into the member  11 , mounting the spring about the projection  19  and inserting the combination into the chamber  3 . 
     Advantageously, in the present invention the inner surface of the chamber  3  does not necessarily have to be perfectly cylindrical and can present ovalization phenomena, which however do not compromise the functionality of the device in question. This is because the seal for the piston  12  is effected against a part  11  which does not present any shape irregularities as it is formed in one piece, is easily mouldable and, because of its shape, is easy to form without shape defects or residual stresses which could lead to ovalizations. The member  11  is fixed to the cylinder both by the annular seat  6  and by the annular projection  23 A provided in its front portion. 
     In particular, that region of the member  11  involved in the sliding of the piston is not used for fixing the piece  11  to the pushbutton; advantageously between that region and the pushbutton a clearance is provided which does not enable any ovalized walls of the chamber  3  to deform the member  11  in that region. 
     The alternative embodiment illustrated in  FIGS. 3 and 4  is particularly suitable for use with substances of low viscosity such as deodorant sprays etc., which have to be atomized during dispensing. 
     Those parts functionally similar to the parts already described previously are indicated by the same reference numerals, and their description will not be repeated. 
     The pushbutton  2  comprises a member  11  presenting a cylindrical portion  11   a  from which a frusto-conical portion  11   c  extends, connected to a front portion  11   b . A passageway  22  functionally similar to that of the preceding embodiment is provided in the frusto-conical portion. The front portion  11   b  in this case has a diameter less than the cylindrical portion  11   a  and is inserted into a plug  30  which frontally closes the chamber  3  in which the dispensing hole  15  is provided. The plug  30  is fixed to the member  11  by an annular projection  23 A which by interference sealedly engages those surfaces defining the chamber  3  in which a suitable groove  24 A is also suitably provided. A hole  31  is axially provided in the front portion  11   b  to act as a guide means for the appendix  16  (cooperating with its outer surface  16 B) and has the same function as the previously described ribs  20 . 
     Also in this case the appendix  16  presents a peg-like sealing portion  16 A which besides blocking the dispensing hole  15  provided in the member is sealedly slidable in a hole  31  provided in the portion  11   b  facing the dispensing hole  15 . 
     Advantageously at the interface surface between the plug  30  and the front portion  11   b  of the member  11  there is provided at least one passageway  34  communicating with the chamber  3  and arranged to conventionally generate a vortex flow of the fluid to be dispensed. 
     Again in this embodiment there is provided, in the end of the chamber  3 , an escape hole for any air present between the rear part of the piston  12  and the end of the chamber  3 .