CA1238299A

CA1238299A - Liquid sprayer

Info

Publication number: CA1238299A
Application number: CA000458111A
Authority: CA
Inventors: Francisco Rodriguez Gazulla
Original assignee: Monturas y Fornituras SA
Current assignee: Meadwestvaco Calmar SL
Priority date: 1983-07-14
Filing date: 1984-07-04
Publication date: 1988-06-21
Also published as: FR2548927B1; ZA845150B; MX160339A; ES273524U; IT8421832A1; AU565310B2; AU3046784A; DE3425478C2; GB2143286A; GB8417304D0; ES273524Y; GB2143286B; IT8421832A0; US4606480A; IT1174045B; FR2548927A1; DE3425478A1

Abstract

ABSTRACT OF THE DISCLOSURE

A liquid sprayer comprising a cylinder defining a pump chamber in which there is housed a piston capable of sliding between positions of minimum and maximum insertion respectively. The piston is hand operated by a trigger and is urged to the minimum insertion position by a spring and in said minimum insertion position, the cylinder free volume is at least 3.33 times larger than the free volume in the maximum insertion position of the piston in said cylinder.

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Description

~L~3~3~9~3 ', Thea invention relates to a liquid sprayer of the type comprising: a body having therein a cylinder defining a pump chamber, a discharge conduit and a passage between said chamber and said conduit, with a port Zooming a valve teat on the conduit side ox said passage; a stem housed in said do charge conduit having an end forming a valve body capable ox sealingly engaging said port; a first spring urging said stem end in engagement with said port; a tubular piston extended by a dip tube and capable of sliding within said cylinder between a minimum insertion position and a maximum insertion position and having a check valve controlling the communication between the alp tube and the pump chamber; a second spring urging said piston to the minimum insertion position thereof In said cylinder; a Jo : rocking trigger adapted to cause the sliding movement of said piston:; means for mounting sate trigger to said I, body; and means for attachment to a liquid containing : 20 receptacle. 'I
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the known sprayer of this typo have certain 'i drawback. One of Tao drawbacks (occurring particularly when the pump Shaker has large dead .

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souses even when the piston it in the maximum insertion position thereon in the chamber and even when the spring urging the stem is very powerful) it that, on first use, namely when the pump chamber it full ox air only, several piston stroke are required to expel such air.
A further Arabic is that the first and/or last amount of liquid discharged each tome the posts it operated is sprayed at a low pro sure and therefore is reduced to dripping or a weak jet which doe not hit the target, whereby, on the one hand liquid it wasted Audi on the other, it may fall where not wanted.

Further drawback arise with the regular attachment systems or the sprayer body to the means for coupling to a receptacle. This means usually comprises a screw cap and in the usually known models the sprayer body is attached -to the screw cap with a tight press fit between the screw cap and the sprayer body, causing material fatigue.
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SIAM OF THE INVENTION

The object of the invention US to provide a sprayer of the above described type whereby the said drawback are overcome at the same time as the advantages ox the ; known sprayers are maintained. i, The first named drawbacks are overcome with a sprayer t ,.
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~23~3299~3 of the type described on which in the minimum Insertion it position ox the piston in the cylinder, the free volume of the pump chamber and of the passage between said check valve and the valve formed by said Tao and said port is at least 10/3 time larger than the free volume it the maximum insertion position ox the piston in the cylinder.

With the above feature, in view ox the low value of said dead spaces, a high pressure is reached in the pump chamber and which it required to overcome the force of said first spring. Consequently, when the pump chamber 1 is full ox air, a jingle piston stroke is practically puff lo tent to expel it.

Furthermore, when the pump chamber contains liquid:
to be sprayed, the latter it always discharged under great force since, if the pressure in the pumping chamber lo is insufficient, the first spring closes the passage between the discharge conduit and the pump chamber. Thus dripping or wear tots are avoided. :

To attain the aforementioned volume ratio between the :
: two end positions ox the piston it the cylinder, according Jo to the~in~ention the piston is provided with a front surface wish in the maximum insertion posi~lon of the :
pow yin the cylinder engages the upper inner surface : 25 of the cylinder, said front Ursa being interrupted by - I :
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9L~3~ 9 the cavity of the tubular piston and by a longitudinal annular grooms which is generally coaxial with the piston and adapted to contain the whole ox the second spring it the maximum compression position thereon.

~urther~ore, the position of the said check valve in the cavity ox said piston it area close to the said .
front surface and preferably the pyre ox the side surface ox the piston closet to the front surface thereof it of generally frustoconical shape, said frustoconical portion partly confronting said passage in the maximum insertion position of the piston in the cylinder Therefore, in the minimum insertion position ox the piston, the pump chamber free volume is formed by that of the chamber itself (namely the volume comprised between the front surface of the piston and the upper inner surface of the cylinder), plus the volume of the longitudinal annular slot, that of the piston cavity up to the check valve . that of the frustoconical gap between the piston and the cylinder and that of the passage up to the seal wormed by the stem. wince these four last named Volume are relatively small and are the only ones remaining free in the maximum insertion position of the pi ton the ratio between the maximum and minimum volumes is high.

According to a further feature of the invention the 27 piston it provided with an external transverse annular notch . I

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housing a sealing ring and the piston it formed from a hard plastic 8 material, particularly, polyamide, polypropylene or an acutely resin. I

Aye according to the inYentiO~p the coupling mean for the trigger to the body comprise a cylindrical shaft integrally attached to the trigger and a concave mounding integral with the body having the shape ox a circular arc greater than a half-circle and having an internal radius generally equal to that of the said cylindrical shaft, thereby facilitating the assembly of both part.

the lower part of the sprayer body opposite said cylinder it generally cylindrical and the means or the attachment thereof to the liquid containing receptacle comparison internally threaded cap and according to the invent on said cap it provided with an annular axially extending projection the outer side Ursa of which is Jo Jo generally ~uxtaposea to the inner surface of said lower:
part which is provided with a portion adjacent the edge :
: ~20 thereof which is externally tapered from said edge said : Lowry part being provided with longitudinal slits to provide it with radial flexibility and wherein there 18 a cap sheath which laterally covers said cap and said lower part said sheath hazing an upper orifice having a I: 25 smaller diameter than said tapering section, said orifice I, :
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be in tapered also . This arrangement overcome the above mentioned drawbacks concerning the attachment ox the sprayer body to the cap without causing fatigue problems for the material.

Jo determine the relative transverse potion of the sheath and the cap, the invention contemplates that the inner surface of the sheath and/or the outer wide surface of the cap should be provided with axially extending grooves and or the relative axial positioning of both parts, the cap sheath it provided, in the orifice thereof with cap retaining means or toe cup and the sheath ore welded together ultrasonically.

Vito reference to a communication between the interior of the vessel and the sprayer other than that provided by the dip tube according to the invention the tubular piston it provided at the end thereon opposite to said cylinder with a external frustoconical surface, said oat being provided with an axially extending space adapted to : guide the piston snugly, said space having a tapering I:
surface adapter to recei~e:the tapering portion of the piston snugly. ` :

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: owe facilitate the understanding of the foregoing reference it: made hereinafter to the accompanying essay . : . 70 - :-' : .; .
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ox drawing itch in view ox their explanatory nature, should be deemed to be devoid of any limitation on the scope ox legal protection being applied or.

Figure 1 it a axial cross emotion view of the liquid I.
sprayer ox the invention, showing the minimum insertion position of the piston in toe cylinder, the cover being in the closed position.

Figure 2 it a similar view to figure 1, but showing the Max us insertion position of the piston in the cylinder, the cover being in the mixed open petunia. ¦
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Figure 3 it an enlarged axial cross section view of the end ox the tubular piston opposite to the cylinder, shown engaging the miner surface ox the axial space ox the cap. I
i Figure 4 it a rosy section view of the Tom figure 5 it a perspective vie on a larger scale and , : partly in section of the lower portion of the sprayer : : body, ox thy cap and of the cap sheath. :

Figure 6 it an axial cross section vlew9 on a larger;
scale ox on alternative embodiment of the end of the : discharge conduit and nozzle holder. :

i Figure 7 is a axial 3eotion vleW9 on pa larger scale, I;: of an alternative embodiment of the piston.

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3LX~ 99 the liquid sprayer according to the invention has a body 1 forming generally the framework ox the sprayer, I
at the same tire as it defines important parts thereof.

The axial portion of the body 1 is provided with an outer wall 2 the lower part 3 ox which is generally cylindrical and is provided with a portion 4 (Figure 5) adjacent the lower edge 5, the latter being preferably widened. Said portion 4 is provided with a fru~toconical outer surface 6 which tapers out from the edge I Said lower part 3 is provided with a plurality ox longitudinal slits 7 providing the lower portion with radial resilience suitable or mounting the sprayer, as will be described~hereInafter In the interior there is a cylinder 8 defining a p chamber 9 and an upper miner Syria 10, which is a portion of the inner surface ox a wall 11 having a~3kirt 12 extending therefrom the wall 11 is extended at the front end thereof 20~ with a cover 13 through a thin portion which acts a a hinge and allows the over to pivot, the o'er being prude with a nob 15 allowing it to be seized. An external ridge 16 is adapted, when the cover is swung back, to snap into a cavity 17 of the wall 11, whereby the coyer it held in a fixed open position. the nob 15 it provided lo :!
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with a lip 18 and an sternal tapering.~houlder 19 adapted to cooperate in a fixed closed position to be described.

In the trainers part of the body 1 there it a discharge conduit 20 which it surrounded on the to wide thereof with the wall 11 and on the side thereof with the irrupt 12. Said condtlit 20 communicates with the pump chamber 9 over a passage 21 which ha at the conduit 20 . end thereon a preferably circular port 22 forming a valve seat. `

The body is also provided with a concave mounding 23 having the shape ox a arc greater than a half-c~rcle.
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In the discharge conduit 20 there it a stem 24 the cross section ox which is smiler than that ox the conduit 15 20 and which is preferably three lobed. The sprayer US
Allah provided with a nozzle 25 contained in a nozzle holder :
26 provided with two coaxial cylindrical portions 27 and Jo 28, one of which snugly surrounds the external surface ox : the conduit 20, contacting also the wall 11, while the I¦ 20 other it fitted to the inner Ursa ox said conduit. Said 1;
nozzle holder is provided with a lower protuberance 29 and a ~rustoconical groove 30 which respectively engage said lip 18 and frustoconical shoulder 19 to provide for the above mentioned axed closed position.

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~313;;~9 The end of the discharge conduit and the item associated therewith such as the nozzle solder, the nozzle and other may be embodied as illustrated it Figure 6. This shows the discharge conduit 20 containing therein the stem 24 which is also thee lobed the wall 11 it extended at the front end thereof with a cover 113 through a thinner portion 114 acting a a hinge and allowing the cover 113, which is provided with a nob 115 or holding purposes, to pivot. There are two external ridges 116 (only one of which is shown in the figure) adapted for cooperating in a fixed closed position as indicated hereinafter. In the interior, the cover 113 has a stem 119 provided with a tapering end to seal the nozzle passage.

In the embodiment of Figure 6, the nozzle 125 is contained in a nozzle holder 126 which, in this case, has a cylindrical portion 128 which engages the inner surface of the conduit 20. This nozzle holder 126 is provided at the front end thereon with a notch, not shown, in which the flaring tabs 118 engage in the mixed closed position.

The said stem 24 it adapted to move lengthwise and is I; provided with a preferably frustoconical end 31 as a valve body which it adapted to engage the port 22 and seal it.
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the stem is also provided with a shoulder 32 and a first spring 33 urging the said end 31 of the stem 24 :

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against the port 22 it disposed between the shoulder 32 and the end ox the inner cylindrical portion 28.

In the concave mounding 23 there it mounted a trigger 34 by means of a cylindrical shaft 35 having a diameter substantially equal to that of the arc forming the mounding Conner Said shaft extends between two wings 36 of the trigger, connected by the front portion 37. Said front portion it provided with a straight portion 38 which may engage the lower portion of the discharge conduit 20 9 SO thaw the latter limits the possibility of pivoting of the trigger in one direction. On the other side of the cylindrical shaft 35, the trigger it provided with two arm 39J disposed fork wise and having a curved end surface 40.

I The distance prom the shaft 35 to the operative area of the front portion 37 it much greater than the distance from said shaft by the curved surface 40, whereby a force applied to said frost portion is notably increased at said curved end surface. the trigger is mounted in -the moulding;23~by pressing the shaft 35 against the mounding opening, whereby this yields resiliently and thereafter no twins the trigger .
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A tubular piston 41 is slidingly mounted in the cylinder 8 and is made of herd plastics material, such a 25~ polyamide, polypropylene or an acutely resin.

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assay 9 The longitude met cavity 42 ox the tubular piston 41 it extended by a dip tube 43 firmly attached to the piston and which communicate with the bottom ox the receptacle (not shown). The piston it provided at the top end thereof with a front surface 44 which in the maximum insertion position ox the piston in the cylinder bears agate the upper inner surface 10 of the cylinder.
Said piston is provided with a longitudinal annular groove 45 substantially coaxial with said cavity and both the groove and the cavity interrupt the said front Sirius The piston 41 comprises a check valve 46, preferably :
formed by a ball 47 which may engage a valve seat 48 former in the cavity 42. Discontinuous shoulders prevent the ball from coming out of the cavity 42~ The valve 46 is located in an area close to the surface 44 such that the space between the ball and the mouth ox the cavity it Molly 1 .

With m the cylinder 8 there is Allah a second spring 50 between the upper inner surface 10 and the bottom of ; the groove 45. In the max~mlm insertion position of the ::
piston, the spring is compressed wholly within the groove.
: the portion 51 of the piston adjacent the front surface : 44 it substantially frustoconical? said portion portly ¦
Jo confronting the passage 21 in the maximum insertion position of the piston. The provision of said frustoconlcal portion provide small gap between the : cylinder and the piston, aiding in the evacuation of the ' I :1 : I
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residual air and/or liquid in the maximum insertion position ox the piston in the cylinder.

In the minimum insertion position ox the piston, the free volume it wormed by the volume of the pump chamber plus the volume ox the grow that of the piston cavity to the valve 47, that of the frustoconical gap and that of thepQs~age 21 up to the end 31 of the stem. Since these four last named volume are relative small an are the only ones remaining tree in the maximum insertion position of the piston, the ratio between the maximum and minimum cylinder volumes is at least 10:3 and therefore the pressure created in the pump chamber it at least 4.33 kg/cm2 (about 62 lbs/in2).

The first spring 33 is wormed in such a way that a high pressure it required in the pump chamber 9 to : : overcome the force thereof, which pressure, when applied ; to the end 31 of the stem 24 lifts the said end from the : port 22 and thereby opens the discharge conduit 20. When the sprayer 19 used for the first time and alto whenever ; 20 the pump chamber 9 contains substantially only air, Jo : obtain the pressure required for opening the discharge }
conduit, it it practically necessary for the piston 41 to react the upper inner surface 10 ox the pump chamber. In .
this way, it it practically possible to expel all the air ::
from the pump chamber on the first stroke OX the piston, the chamber receive the fluid occupying thy tube 43, at , : I:
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ire t air and then comprising only the liquid to be sprayed. In subsequent strokes of the piston ID the valve 46 jeeps the tube 43 full of said liquid.

When thy pump chamber it thus pull ox liquid, a high pressure it Allah required in the pump chamber to open the Decker conduit. Therefore the liquid it force out and the weak sprays or dripping at the beginning and the end of each pump stroke a it usual with other sprayers, do not occur.

To seal toe pump chamber, the tubular pun it provided on the outside thereof with a transverse groove 52 in which there is housed an 0-ring 53 of a material which is more resilient and softer than that of the tubular piston. the material of the Neal it Bun N, neoprene, polyvinyl chloride, copolymers7 polythene and polypropylene in blends, nylon iron silicone, :
chloroprene or the like and it chosen appropriately in i .
terms of the nature of the liquid to be sprayed. !

The Tory piston 41 may not be formed from B
material swishes indicated for the 0-ring, since it Gould be excessively soft. :

: The piston it also provided with a transverse annular :
shoulder, the lower surface 55 of which is engaged by the .
curved surface 40 ox the forked arm 39 ox the trigger 34 15.

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The operation of this arrangement of the trigger and piston it self explanatory. One end position of the trigger it defined by the abutment action of the straight portion 38 ox the trigger with the discharge conduit 20 (Figure 1). the other end position it provided by the piston wreck itself (figure 2). Obviously the action ox the spring 50 tends to urge the trigger into the Figure 1 position.

From said shoulder 54, the piston extends to an end 56 (opposite to the cylinder 8) huh it provided with a tapering external surface 57 (Figure 3). Further reverence will be made to these parts here~na~ter.

Figure 7 illustrates a further embodiment ox the piston. In this case, the piston 141 it provided with a section 142 of smaller diameter than the cylinder diameter and said section 142 it covered by a jacket 143 of a resilient material similar to the material contemplated for Jo the O-ring joint 53. The jacket 143 it attached to the piston section 142 by means of the inwardly extending annular rib 144 ox the jacket which engage in the corresponding annular groove 145 of the piston.
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The jacket 143 it provided at the end thereon adjacent ; the receptacle with an outwardly directed appendix generally parallel to the jacket, folder over in kiwi The outer surface of the appendix snugly engage the cylinder 90 that I

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~123B299 said appendix worms a sealing member. between the upper portion ox the jacket and the cylinder in Figure 7 there it a gap 147 facing the passage 21 it the maximum section position ox the piston 141 in the cylinder The purpose ox this gap it equivalent to the gap formed by the tapering section 51 of the pre~ious7g described embodiment.

The sprayer it provided with meat for the attachment thereof to the receptacle containing the liquid to be sprayed. such means comprises an internally threaded screw cap 59 and a cap sheath 60 which cooperates with the lower part 3 ox the sprayer body 1 (Figure 5).

Above the internally threaded region 61 thereon the screw cap 59 is provided with an axially extending tubular portion 62 the outer lateral surface 63 ox which substantially juxtaposed to the inner surface of said lower part 3. Preferably the portion 64 of the portion 62 ;
closer to the internally threaded region I has a larger :, diameter and in such case said lower part 3 Allah ha a larger diameter. The internally threaded region 61 it :
provided with discontinuous portions provided with axially extend my gnarling 65. At the lower end ox the screw cap there it at least one annular groovy 66 Ed although only ` one it shown there may be more than one grove : : .
Coccal disposed with the portion 62 and with the :
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' err cap there it an axially extending bore 67, the circular Hall 68 of which is connected by radially extending we 69 to the portion 62, making it more rigid. Said bore (figure 3) guide the piston 41 by means of the tabs 71 thereof and it provided with a tapering surface 70 having a different angle than that of the surface 57 of the lower end 56 of the piston.
Wren the put is at ret, the end 56 thereon bear with its tapered surface 57 on the surface 70 of the bore 67 and therefore seal the receptacle from the outside environment.

The sheath 60 of the screw cap 59 laterally covers said screw cap and said lower part 3 ox the sprayer body 1 and is provided with an upper orifice 72 having a smaller diameter than that of the external tapered surface 6 ox the portion 4 of said lower part 3. Said orifice 72 is also tapered. The sheath 60 and the body 1 I are assembled together before assembling the screw cap ::
: by facing the tapered orifice 72 with the tapered surface : 20 6. The smaller diameter of the orifice causes joy lower part 3 of the body 1 to yield resiliently radially inwardly at the portion thereof contain m g the slits 7 Jo until said portion has moved beyond the rolled over portion 73 of the sheath 60, at which time said portion recover the original diameter thereof and stubbles the relative position ox the body 1 and the sheath 60 5 with the free ::

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3~2 go ergs 74 of the rolled over portion blaring against a uric 75 of the larger ought diameter portion 64 of the portion 62 ox the screw cap 59.

Thy sheath 60 is provided it the interior surface thereon with kn~rlings 76 which engage the knurlings 65 of the strew cap to ensure the relative position of both, particularly it the transverse direction. Furthermore the sheath it provided with as many internal projections 77 as there are grooves 66 and they are ox mating shape with the grooves 667 the mutual engagement thereof ensuring the relative position of thy sheath and the screw cap in an axial direction. The sheath and the zap :
may also be joined together by ultrasonic welding; in this case the knurlings 65 and 76 an rib 77 and grooves:
: 15~ 66 are not required.

Toe operation of the spray has been described in part in the previous paragraphs. Wevertheless9 a succinct I: : description of the operation thereon it given below The : as smbly of the different part of the sprayer has already been described. Starting out prom the position of Figure 1 : : with the sprayer coupled to a receptacle it the first :
place the cover 13 is lifted by teak m g hold ox the nob 15 and snapping the over into the position ox Figure 2. The trigger 34 it pressed to cause the piston 41 to penetrate in the cylinder 8: against the force of the wrung 50. :
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isles During the upward stroke of the piston, the pressure in thy pump chamber 9 Roy, whereby the check valve 46 remain closed and therefore there is no communication between the pump chamber and the receptacle interior.
join the air in said chamber reaches sufficient pressure to overcome the force of the first spring 33, the stem 24 it moved and the air in the chamber 9 slows through the assuage 21 and discharge conduit 20 and out to the atmosphere through the nozzle 25, almost all the air being expelled from the chamber. Ryan the trigger is released, thy second spring causes the piston to move down, creating a depression in the chamber 9 which, on the one ; hand closes the valve formed by the end I of the stem and the port 22 of passage 21 and furthermore opens the check valve 46, by separating the ball 47 from the Allah teat I During the downward stroke of the piston 41, the liquid contained in the container rise up the dip tune 43 and fills the pump chamber 9, until at the one of the downward stroke, the sprayer is ready for the first liquid spray. This spray is achieved by pressing the trigger 34 again and, as stated above the spray i not : produced until there has been obtained in the pump chamber 9 a pressure high enough to overcome the first spring 33, whereby the spray Tarts under a high pressure and is : 25 sharply cut off in case of a fall in said pressure, thereby .
avoiding dripping and short sprays, :' I: :
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Claims

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. A liquid sprayer of the type comprising:

- a body having therein a cylinder defining a pump chamber, a discharge conduit and a passage between said chamber and said conduit, with a port forming a valve seat in the conduit side of said passage;

- a stem housed in said discharge conduit having an end forming a valve body capable of sealingly engaging said port;

- a first spring urging said stem in engagement with said port;

- a tubular piston extended by a dip tube, capable of sliding in said cylinder between a minimum insertion position and a maximum insertion position and having a check valve controlling the communication between said dip tube and said pump chamber;

- a second spring urging said piston to the minimum insertion position thereof in said cylinder;

- a rooking trigger adapted to cause the sliding movement of said piston;
- means for mounting said trigger to said body; and - means for attaching the sprayer to a receptacle containing liquid to be sprayed, wherein in the minimum insertion position of the piston in the cylinder, the free volume of the pump chamber and said passage comprised between said check valve and the valve formed by said stem and said port is at least 3.33 times greater than the free volume in the maximum insertion position of the piston in the cylinder.

2. The liquid sprayer of claim 1, wherein said piston is provided with a front surface which in the maximum insertion position of the piston engages the upper inner surface of said cylinder, said front surface being interrupted by a cavity of the tubular piston and by a longitudinal annular groove generally coaxial with the piston and adapted to contain the whole of said second spring in the maximum compression position thereof.

3. The liquid sprayer of claim 2, wherein said check valve is located in the cavity of said piston in a region adjacent said front surface.

4. The liquid sprayer of claim 2, wherein aid piston is provided with an external transverse annular groove in which a sealing ring is housed.

5. The liquid sprayer of claim 2, wherein the portion of the piston side wall closest to the front surface of the piston is generally frustoconical, said frustoconical portion partly confronting said passage in the maximum insertion position of the piston.

6. The liquid sprayer of claim 2, wherein one portion of the piston is of smaller diameter than the diameter of the cylinder and said portion is covered by a jacket of resilient material, one of the ends thereof being provided with an appendix which extends outwardly, the outer surface of said appendix snugly engaging the cylinder wall forming a sealing member, there being a gap between part of the jacket and the cylinder, said gap confronting said passage in the minimum cylinder volume position of said piston.

7. The liquid sprayer of claim 1, wherein said piston comprises a hard plastics material, particularly polyamide, polypropylene or an acetal resin.

8. The liquid sprayer of claim 1, wherein the means for attaching said trigger to said body comprises a cylindrical shaft integral with said trigger and a concave moulding integral with said body, having the shape of an arc greater than a half circle and having a radius generally the same as that of said cylindrical shaft.

9. The liquid sprayer of claim 1, wherein one end position of the trigger is determined by the end of the inward sliding of the piston in the cylinder and the other end position is determined by contact of a portion of the trigger with a surface of the discharge conduit.

10. The liquid sprayer of claim 1, in which the lower part of said body opposite said cylinder is generally cylindrical and in which the attachment means to the liquid containing receptacle comprises an internally threaded screw cap, wherein said screw cap has an axially extending annular portion the outer side surface of which is generally juxtaposed the inner surface of said lower part, this latter having a portion adjacent the edge thereof which is externally frustoconical with an increasing diameter from said edge, said lower part having longitudinal slits providing radial resilience and wherein there is a screw cap sheath covering the sides of said screw cap and said lower part, said sheath having an upper orifice of a diameter smaller than that of the frustoconical portion, said orifice having a frustoconical shape.

11. The liquid sprayer of claim 10, wherein the inner surface of said sheath and/or the outer side surface of said screw cap are provided with axially extending knurlings.

12. The liquid sprayer of claim 10, wherein said screw cap sheath is provided in the inside of the lower end thereof with means for retaining said screw cap.

13. The liquid sprayer of claim 10, wherein said screw cap sheath and said screw cap are connected together at their respective ends adjacent the respective lower openings thereof by ultrasonic welding.

14. The liquid sprayer of claim 10, wherein said tubular piston is provided is the end thereof opposite said cylinder with an outer frustoconical surface, said screw cap being provided with an axial bore snugly guiding the piston, said bore having a frustoconical surface with which the frustoconical portion of the piston engages.