Dispenser for dispensing atomized fluids under pressure, provided with a shut-off element operated by the pressurized fluid

Abstract: The invention provides a dispenser for dispensing atomized fluids under pressure, provided with a shut-off element operated by the pressurized fluid. The dispenser comprises a compression chamber housing a movable piston (13) from which there projects an appendix (17) which, when in the rest state, is urged by a spring (15) to seal a discharge hole (7) provided in a body closing said chamber, which communicates with a seat into which the end of the stem (3) of a pressurized fluid pump can be inserted; when the fluid pressure within said chamber overcomes the resistance of the spring (15), the piston (13) moves and its appendix (17) frees the discharge hole (7). That end of the piston (13) close to its appendix (17) is slidable in a sealed manner within a cavity in a bush (8); a communication duct between the compression chamber and the discharge hole (7) is freed only when said end of the piston (13) emerges from the bush cavity on withdrawing.

Description: This invention relates to a dispenser for dispensing atomized fluids under pressure, provided with a shut-off element operated by the action of the pressurized fluid. To dispense pressurized liquids in finely atomized form it is known to use manually operated pumps with a hollow liquid exit stem on which a dispensing head is mounted incorporating a chamber at which the pressurized liquid arrives from the pump stem. The pressurized liquid is discharged to the outside in atomized form after passing through a discharge hole in which a series of spiral channels are provided leading to a chamber wherein the fluid undergoes a strong swirling movement before being expelled to the outside. To achieve good and constant atomization without liquid dripping outside the discharge hole, the liquid pressure at this hole, when dispensing commences, must be sufficiently high from the beginning. This problem has been previously partially solved by constructing and using pumps from which the liquid is discharged only when its pressure is sufficiently high. Such pumps are however of rather complex structure and their cost is fairly high. In addition the liquid delivered by the pump tends to lose pressure as dispensing commences, in passing through the various passages provided in the dispensing head. If the fluids to be dispensed tend to dry, so obstructing fluid passage through the discharge hole (which very easily happens, for example, if the fluid is hair lacquer, dressing fluid or the like), the discharge hole must be closed on termination of each dispensing operation in order to isolate from the air the fluid residues present between the pump and the discharge hole in the dispensing head. To overcome this problem, US-A-4,182,496 describes a dispensing head having a compression chamber housing a slidable piston which is provided with a lip sealingly closing at one end said chamber and also with an appendix extending towards a discharge hole provided in an insert delimiting the compression chamber at its other end. The dispensing head has a seat for receiving the free end of the stem of a pump, said seat communicating with said compression chamber through a passage opening in an intermediate position between the lip and appendix of the piston. Acting on the piston there is a spring which when under rest conditions urges its appendix free end against said insert to hermetically seal the discharge hole, hence isolating any fluid present in said chamber from contact with the air. When the pump is operated, the pressurized fluid reaching said chamber causes the piston to move against the action of the spring, with consequent withdrawal of the free end of its appendix from the discharge hole. The dispensing head of US-A-4,182,496 and that (analogous but less sophisticated) represented in DE-A-1750186 have the drawback that even if the liquid reaches a high pressure in the compression chamber before the movable piston begins to move from its rest position by overcoming the action of the spring which acts on it, there is in any event some dripping of the liquid (consequent on a considerable reduction in its pressure) passing through the discharge hole on commencement of dispensing (with consequent formation of incrustations on the outside of the discharge hole). A similar negative phenomenon occurs immediately before the piston appendix closes the discharge hole on termination of each delivery. In this respect, on commencement of dispensing, when a certain pressure is reached in the compression chamber the piston begins to gradually move, with gradual withdrawal of the end of its appendix from the discharge hole to gradually open liquid passage to the discharge hole. The discharge hole is completely free only after the free end of the piston appendix has moved sufficiently far from it; however, before this position is reached, a certain quantity of liquid will already have been discharged flowing through a narrow path casing it to lose pressure. The reverse phenomenon occurs when delivery ceases. The EP-A-0688608, published on 27.12.95 and which is part of the state-of-the-art in the sense of Article 54(3) EPC, discloses a device comprising a support 7 defining an internal cylindrical wall 15 having two axially opposite openings 9, 11 in correspondence of the first of which there is provided a seat for housing the free end of the stem of a pump, while in correspondence of the second opening there is positioned a body 12 with a nozzle 13 which faces the free end of an obturator 17 extending from a plunger 23, the obturator being guided by a sleeve 16 having a tubular extension 20 into which a cylindrical portion 22 of the obturator can sealingly penetrate. The plunger 23 has two spaced annular lips 24, 25 which sealingly engage the cylindrical wall 15 of the support 7: the plunger has also radial apertures 26 which put the hollow space 27 between the lip 25 and the opening 9 into open communication with the space 28 surrounding the portion 22 of the obturator, the latter being urged by a spring 29 so that - at rest - the free end 18 of the obturator 17 sealingly closes the nozzle 13. When the device is actuated for discharging nebulized liquid into the atmosphere, first the end 18 of the obturator 17 is moved away from the body 12 thus leaving the nozzle 13 free and only subsequently the cylindrical portion 22 of the obturator leaves the tubular extension 20 to permit free passage of the pressurized liquid from the spaces 27 and 28 to the nozzle 13. In such a way, since the nozzle 13 (whose size is very small) is completely open and free when the liquid under pressure reaches it, it is possible to avoid dripping of the liquid outside the nozzle. The present invention relates to a dispenser of the aforesaid type, as described in US-A-4,182,496 i.e. able to hermetically seal the dispenser discharge hole when under rest conditions The problem to be solved by the invention is to ensure a substantially constant pressure of the dispensed fluid, both during opening and during closure, hence to prevent fluid dripping. The dispenser of the invention should also be usable with very simple and inexpensive mechanical pumps, which nay deliver their pumped fluid at non-constant pressure. Finally, the dispenser of the invention should preferably enable fluid dispensing to commence in a sudden manner to cause expulsion of any substances which may have previously deposited in the discharge hole. These and further objects are attained by a dispenser comprising a hollow head provided with a seat for its connection onto the free end of the stem of a pump and in which there is provided an elongate compression chamber in communication with said seat through an aperture made in said head and delimited at a first end by a body traversed by a hole through which fluid is discharged into the atmosphere, said chamber movably housing a piston provided with a seal lip which delimits and sealingly closes the other end of the compression chamber, from said piston there projecting an appendix the free end of which, when in a rest position into which it is urged by a spring housed in said hollow head and acting on the piston, closes said discharge hole, said appendix being withdrawable from said hole into a dispensing position by the action of a pressurized fluid fed into said chamber and acting on the piston against the action of said spring to allow the pressurized fluid to be discharged in an atomized state from said chamber through said discharge hole, the cavity of said head housing a bush traversed by a hole into which said piston appendix is inserted and through which it extends, characterized in that from said bush there extends a tubular wall defining a cavity in which a portion of the piston close to said appendix can be inserted and can slide in a sealed manner, the length of said tubular wall and of said piston being such that said portion of the piston emerges from the cavity delimited by the tubular wall of the bush only after undergoing an extent of travel sufficient to enable said appendix to withdraw from said discharge hole to allow free discharge of the pressurized fluid originating from said compression chamber through at least one channel provided within said bush and closable by the piston, the movement of the piston under the thrust of the spring from its position far away from said discharge hole to its position in which it sealingly engages said tubular wall causing all the fluid contained in said chamber between such two positions of the piston to be discharged under pressure through said hole. The structure and characteristics of the dispenser according to the present invention will be more apparent from the description of one embodiment thereof given hereinafter by way of non-limiting example with reference to the accompanying drawing, in which: Figure 1 is a longitudinal section through the dispenser in its rest position; and Figures 2 and 3 show the same dispenser in an intermediate position and, respectively, in the final position which it assumes when dispensing the fluid. The dispenser shown on the drawing comprises a hollow head 1 provided with a seat (defined by a tubular wall 2) into which the free end of the hollow stem 3 of a mechanical pump (not shown), of any known type able to deliver fluids under pressure each time it is manually operated, is inserted and retained. In the head 1 there is provided a compression chamber 4 which communicates with the said seat via a hole 5. The cavity of the head 1 is closed by a body 6 (which is inserted into and snap-locked within the cavity, as is clear from the figures) traversed by a hole 7 through which the atomized fluid is discharged into the atmosphere, as explained hereinafter. The body 6 houses and retains a bush 8 which, in that surface thereof resting against the body 6, comprises spiral channels 9 leading to a central chamber 10 immediately upstream of the hole 7. At their outer end the channels 9 open into an annular chamber 11 into which there open one or more passages 12 passing through the bush 8. The cavity in the head 1 houses a piston 13 which can slide therein and is provided with a lip 14 which sealingly slides against a corresponding cylindrical surface of the cavity within the head 1. As can be seen from the drawing, on the piston 13 there acts a compressed spring 15 the force of which determines the delivery pressure of the fluid expelled from the hole 7. Finally, it can be seen that from that end of the piston 13 facing the body 6 there projects an elongate appendix 17 passing in a sealed manner through a hole provided in the bush 8 and having its free end urged (when the dispenser is in its rest state as shown in Figure 1) against the body 6, to hermetically seal the discharge hole 7. The dispenser structure described up to this point is substantially analogous to that of US-A-4,182,496. An essential fundamental characteristic of the dispenser according to the present invention is that from the bush 8 there extends a tubular wall 18 defining a cylindrical cavity in which a cylindrical portion of the piston 13 close to the appendix 17 can be inserted and slide under sealed conditions. To clearly illustrate the characteristics of the dispenser reference will now be made to the figures to explain its operation. It will be assumed that in the rest state shown in Figure 1 the free end of the appendix 17 hermetically seals the hole 7, to hence completely isolate any fluid residue present in the central chamber 10 from contact with the air. When in this state the chamber 10, the annular chamber 11 and the passages 12 do not communicate with the compression chamber 4 because said piston cylindrical portion seals against the inner surface of the tubular wall 18 of the bush 8. It will now be assumed that the head 1 is lowered (with respect to the figure) and with it the stem 3. This causes operation of the pump of which the stem forms part, with the result that the pressurized fluid delivered by the pump and rising along the stem 3 into the compression chamber 4 acts on the piston 13, 14 to cause it to move towards the right (with respect to the figures of the drawing), compressing the spring 15. Together with the piston there also moves the appendix 17, which withdraws from the hole 7 to retract into the chamber 10. In the initial stage of the piston movement, while there is sealed contact between the piston and the tubular wall 18 of the bush (Figure 2) there is no communication between the compression chamber 4 and the chamber 10, from which however the appendix 17 is retracted. As the piston continues to move towards the right (Figure 3), when a predetermined pressure is attained in the chamber 4 the piston is completely freed from the tubular wall 18 and the pressurized fluid penetrates violently into the chamber 10 (and is hence expelled to the outside of the hole 7 in finely atomised form, at high pressure from the very commencement of dispensing) after traversing the passages 12, the chamber 11 and the channels 9. It will be noted that at the moment in which the piston 13 is freed from the tubular wall 18 a free annular passage of relatively large dimensions is immediately created, in that its minimum diameter corresponds to the outer diameter of the piston, which is relatively large, hence the dimensions of this annular passage are immediately much larger than the dimensions of the chamber 10 (which has already been freed by the appendix 17). The result is that the pressurized fluid penetrates violently at high pressure (there are practically no relevant constrictions) into the chamber 10, from which it is expelled at high velocity to remove any residues present in the chamber or in proximity to the discharge hole. Likewise, during closure, communication between the chamber 4 and the chamber 10 is initially and very suddenly interrupted, resulting in immediate loss of fluid pressure within the chamber 10. Only subsequently (although after only an infinitessimally short time) does the free end of the appendix 17 close the hole 7, any fluid residues present in the chamber 10 (which is practically completely occupied by the appendix 17) being pushed out of the hole 7, so preventing the formation of dangerous incrustations. It can be seen that that end of the piston facing the bush, and the bush itself, can be shaped to form an obstacle to be overcome snap-wise an instant before the piston is freed from the tubular wall of the bush, in order to increase the "shooting" effect of the pressurized liquid to the chamber 10 and to discharge. This can be achieved for example by conically shaping the opposing cooperating surfaces of the piston and tubular wall, or by forming a small annular rib, with a respective corresponding annular groove, in one and the other of the two parts. It is very important to note that the described dispenser can be also applied to pumps of very simple and inexpensive structure, even those without the (costly) expedients necessary to ensure that the pumped fluid is delivered only after a predetermined pressure has been exceeded. Moreover, the dispenser can be easily adapted to dispense different fluid quantities by simply varying the dimensions of the tubular wall of the bush and consequently of the piston. The dispenser can be constructed for operation by the finger of one hand (such as that shown on the drawing) or by a lever or the like, in known manner.

Claims: A dispenser for dispensing atomized fluids under pressure, provided with a shut-off element operated by the action of the pressurized fluid, comprising a hollow head (1) provided with a seat (2) for its connection onto the free end of the stem (3) of a pump and in which there is provided an elongate compression chamber (4) in communication with said seat (2) through an aperture (5) made in said head (1) and delimited at a first end by a body (6) traversed by a hole (7) through which fluid is discharged into the atmosphere, said chamber movably housing a piston (13) provided with a seal lip (14) which delimits and sealingly closes the other end of the compression chamber (4), from said piston (13) there projecting an appendix (17) the free end of which, when in a rest position into which it is urged by a spring (15) housed in said hollow head (1) and acting on the piston (13), closes said discharge hole (7), said appendix (17) being withdrawable from said hole (7) into a dispensing position by the action of a pressurized fluid fed into said chamber (4) and acting on the piston (13) against the action of said spring (15) to allow the pressurized fluid to be discharged in an atomized state from said chamber (4) through said discharge hole (7), the cavity of said head housing a bush (8) traversed by a hole into which said piston appendix (17) is inserted and through which it extends, characterized in that from said bush (8) there extends a tubular wall (18) defining a cavity in which a piston portion (13) close to said appendix can be inserted and can slide in a sealed manner, the length of said tubular wall (18) and of said piston (13) being such that said portion of the piston (13) emerges from the cavity delimited by the tubular wall (18) of the bush (8) only after undergoing an extent of travel sufficient to enable said appendix (17) to withdraw from said discharge hole (7) to allow free discharge of the pressurized fluid originating from said compression chamber (4) through at least one channel (12) provided within said bush (8) and closable by the piston, the movement of the piston (13) under the thrust of the spring (15) from its position far away from said discharge hole (7) to its position in which it sealingly engages said tubular wall (18) causing all the fluid contained in said chamber (4) between such two positions of the piston (13) to be discharged under pressure through said hole (7). A dispenser as claimed in claim 1, characterised in that said cavity in the bush (8, 18) has a shape such that it interferes with said piston but is overcome snapwise by the piston (13) at the moment of its emergence from said cavity.

Inventors: ALBINI GIOVANNI, CARLAPPI FRANCO, RUSCITTI TOMMASO, ALBINI, GIOVANNI, CARLAPPI, FRANCO, RUSCITTI, TOMMASO
Applicants: TER SRL, TER S.R.L.
Application year: 1995
Main classification: B05B11
IPC codes: B05B1, B05B11