IL32516A - Valve assembly for dispensing metered amounts of pressurized product - Google Patents

Description

A VALVE ASSEMBLY FOR DISPENSING METERED AMOUNTS OF PRESSURIZED PRODUCT in a? imiaj npVyn1? pinog^ njnys Yin1? isia *m The general subject of the invention concerns a valve assembly for dispensing a metered amouiit of aerosol product on a downward stroke to be mounted to a canister containing pressurized product.

There is available a valve construction for pressurized packages which includes, a removable and replaceable spray head having a depending hollow stem and a separate spring -biased valve plunger carrying a socket arranged to receive the stem. The plunger is arranged normally seated to seal off the interior of the package from the atmosphere. The stem carried an axially extending slot in the wall thereof at the lower end, the length of the slot being selected to define the only passageway for flow of fluid from the package into the stem when the plunger is unseated. The spray head could be removed, cleaned and replaced without loss of fluid from the package. Moreover, change in the rate of spray or spray pattern could be effected by substitution of another spray head carrying a different dimensioned slot, or a different external orifice or dispensing aperture. These so-called "slot valve"constructions have become widely known and accepted, particularly in the dispensing of heavier pressurized products where clogging of the valves is a problem.

However, when one considers the dispensing of metered quantities or doses of product, the valve constructions heretofore available for that purpose fail to provide a Generally, valve constructions heretofore utilized for dispensing pressurized product in metered doses have been provided with internal chambers capable of being filled and purged in accordance with the stroke cycle of a spray head associated therewith. The metering chambers normally either are empty, being filled on the downstroke. and purged on the return, or, normally are in communication with the product and hence filled, dispensing occurring by blocking such communication and establishing communication between the chamber and the atmosphere. Complete filling and purging are not always assured. Most metering type valve con- ■ structions utilize unitary stem and plunger arrangements, thus making impossible the cleaning of the critical passageways by removal, cleaning and replacement of the stem carrying same.

Often, the operator is given the option of dispensing the pressurized product either in metered amounts or continuously. In continuous dispensing, it would be advantageous to utilize the features of the patented valve con-structions above discussed to gain the benefit of the many advantages resulting therefrom. However, the prior art merely presents such option in the form of dual passageways selectively either brought into communication with the metering chambers or bypassing such chambers for continu-ous spray. No dosage valve structures available heretofore are capable of affording such option by providing for substitution of one removable s ra head for another.

Prior "dosage" structures fail to provide for internal control variation in the metering orifice to vary spray rate under the continuous spray option, even if the option may be provided.

Accordingly, the invention provides a valve assembly for aerosol spray packages or the like for dispensing pre-measured dosages of product contained therein wherein the valve assembly includes a cover member to be secured to the package, a hollow housing secured to the cover member and when mounted communicating to the interior of the package, means defining a metering chamber of predetermined volume disposed within the housing for establishing said dosage, and having entry and outlet communicating to the package interior and the atmosphere respectively, perforated gasket means at the said entry and outlet, a spring- biased valve plunger reciprocable within the housing with its valve seat' normally engaged to block entry to the metering chamber, a removable spray head having a depending hollow stem engaged sealingly slidably through said perforated gasket means terminating in a socket formed in the valve plunger and normally blocking communication with said metering chamber, passage defining means formed in the stem arranged at locations for establishment of communication between the package interior and the metering chamber to permit entry of spray material thereinto while preventing outlet therefrom and thereafter to isolate said chamber ■ only whereby to discharge the contents of said chamber, all upon depression of said spray head with at least partial refilling of said chamber effected upon return movement of said sprayhead.

Further, the invention specifically provides the passage defining formations in the form of a longitudinal groove formed in the outer circumferential wall of the stem at the lower end thereof and a through radial passageway formed in the stem wall at a location spaced from said lower end.

The preferred embodiments of this invention will now be described, by way of example, with reference to the drawings accompanying this specification in which: In the drawings, Figure 1 is a reduced fragmentary side elevational view of a pressurized package having the valve assembly according to the invention secured thereupon.

Figure 2 is an enlarged elevational sectional view iudfGCTtgg-? of the valve assembly of Fig. 1.

Figure 3 is a view similar to that of Figure 2, but illustrated in the condition during initial downstroke of the spray head whereupon filling of the metering chamber occurs .

Figure 4 is a view similar to that of Figure 2, but illustrating the condition assumed at the intermediate stage of depression of the spray head.

Figure 5 is a view similar to that of Figure 2 but illustrating the condition assumed when the spray head is fully depressed.

Figure 6 is a view similar to that of Figure 2 illustrating the condition of the valve assembly during pressure filling of the canister.

Figure 7 is a perspective view of the removable cup defining the metering chamber of the valve assembly.

Referring now to the drawings, in Figure 1, there is shown the upper end of a pressurized package designated generally by reference character 20. There is provided a canister comprising a metal cylinder 22 having an upper dome 24 and a bottom end (not shown) all designed to contain the pressure to which such package is subjected. The dome 24 has an upper opening 26 formed with a rolled edge 28 as shown in Figure 1 and the entire valve structure and sprayhead are arranged for securement at said opening 26 in sealing engagement with the rolled edge 28.

The product manufactured and sold to the filler by the valve maker consists of the parts shown in Figure 1 exclusive of the canister 22. These parts are given general characters of reference and the specific details will also be identified. The character 30 is a metal cover member; the character 32 is the valve housing assembled in sealed connection with the cover member; the character 34 is a long, resilient plastic dip tube attached to the housin 32 and the character 36 is s ra head mounted o the valve mechanism contained in the housing.

Only the essential operating parts of the. valve assembly embodying the invention are illustrated in Figures 2 through 6, and it should be understood that details of conventional parts will only be illustrated in those figures where necessary. The cover member 30 preferably is formed of sheet metal and includes, conventionally, a curled over lip formed on the annular edge thereof which provides an annular well by reason of the formation of an upwardly extending central boss 38, the upper wall 39 thereof being shown in Figures 2-5. The cover is secured to the canister by crimping same over the rolled edge 28 of the dome 24.

The valve housing 32 is a separate, generally cylin- drical hollow structure having a flared upper end 40, and a thickened constricted lower end 42 defining a port 42' into which the dip tube 34 is attached. The dip tube 34 is formed of resilient plastic material and extends down to the bottom of the cylinder 22. The dip tube 34 is tightly engaged within the constricted or thickened lower end 42 of housing 32 by means of a split collar 44. The split collar 44 is forced into the throat of the constricted lower end 42 with the tube seized therein and contracts about the tube 34 fractionally holding the same and itself in place.

The housing 32 is secured to the boss, represented b u er wall 9 thereof b ha engaged against the bottom of an annular, perforated gasket 46 which is formed of rubberlike material. The gasket 46 is disposed engaged against the underside of end wall 39 of the boss and the assembly is tightly held in place by suitable crimps or pinches 48 upsetting the metal of the boss inwardly in places around the circumference thereof and under the flared portion 40. The center of the wall 39 is perforated, as at 50, and in accordance with conventional practice, the resulting opening has its edges turned up slightly so as to achieve a sliding and sealing fit between the gasket and the stem of the sprayhead 36.

The valve housing 32 provides an enclosed upper chamber 52 and a lower valve chamber 54, with upper chamber 52 being of greater diameter than lower chamber 54 and set off by annular shoulder 56. A second resilient perforated gasket 58 rests upon the shoulder 56. Said gasket 58 is of a diameter equal to the diameter of the upper chamber 52. The perforations of both gaskets 46 and 58 are substantially equal in diameter and co-axially aligned.

A cup-like annular insert 60 having an outer diameter equal to the diameter of the chamber 52 is disposed within said chamber 52 in a tight, frictional engagement, the rim 62 of the insert 60 being flush with the top of flared end 40 of the valve housing 32 so that it engages the undersurface of the gasket 46. The floor 64 of the cuplike insert 60 is tapered centrally to an opening 66 therein, also co-axial with the perforations of gaskets 46, 58 and opening 50 of wall 39. ' The interior of the cup insert 60 is molded of plastic material and has a predetermined volume capacity to define metering chamber 68. The opening 66 of said insert 60 has a diameter slightly greater than the diameters of the perforations of gaskets 46 and 58. The "dosage" or charge dispensed can be changed by substitution for insert 60, another similar insert but having a different capacity.

The enclosed lower valve chamber 54 will permit the pressurized product to pass up the dip tube 34 and flow into the metering chamber and thence out to the atmosphere unless prevented from doing so by some structure blocking the opening defined by said perforated gasket 58. Obviously, other structure must be present to block the opening 50 in wall 39 as well as the opening defined by the perforated gasket 46. The structure provided to block the opening defined by the perforated gasket 58 comprise a valve plunger 70 which is reciprocable in the chamber but normally is pressed upward by a helical spring 72, the bottom end of which engages the inside of the housing at the thickened constricted portion 42.

The body 76 of plunger 70 is generally cylindrical in configuration, having a reduced diameter lower por seat for the upper portion of helical spring 72. A shallow upwardly opening central axial socket 82 is formed in the valve plunger 70 and is normally co-axial with the perforations of gaskets 46 and 58 and opening 50.

The upper rim 86 of the valve plunger 70 has an inner gallery formation 88 surrounding the socket 82. Axial ribs 90 are provided spaced circumferentially about the inner wall 92 of the housing 32 within the lower valve chamber 54, functioning to guide the vertical reciproca-tion of the valve plunger 70. The ribs 90 can be molded integral with the valve housing 32.

The valve plunger 70 normally is biased upwards by spring 72 so that the upper surface of rim 86 is engaged against the undersurface of gasket 58 defining a valve seat blocking communicationbetween the metering 68 chamber =52 and the interior of the valve chamber 54.

The socket 82 has a central pilot protrusion 94 to engage the axial lower end of the hollow stem 98 to be described.

The spray head 36 has a body or actuator portion 96 and a depending hollow stem 98 having an axial bore 100 defined therein and extending entirely along the length thereof into the body 96. A shallow chamber 102 is provided interior of the actuator body 96 leading to a radial bore 104 of narrow diameter which terminates in a recessed dispensing orifice 106. The bottom end of bore 100 is open.

The stem 98 is selected of a length and diameter sufficient to extend slidably and sealingly through both gaskets 46 and 58 terminating bottomed in socket 82. The stem 98 extends outward of said boss a sufficient distance to permit two stages of movement through said gaskets. The first stage dislodges the engagement of the valve seat of rim 86 with the gasket 58. The second stage will be explained hereinafter. Intermediate the ends of the stem 98, there is provided a radial passageway 108 extending through the stem wall at the upper end thereof. The lower end of the stem wall is provided with a longitudinal groove 110 opening radially outward. The length of said groove 110 and the location of the passageway 108 are selected to establish a careful relationship mandatory to the successful operation of the valve assembly. The location of the radial passage- way 108 is chosen so that when the spray head 36 initially is stroked downward the distance "y", communication is established between the interior of the metering chamber 68 and the interior of the valve chamber 54 only through the 1 10 groove %#e and without connecting the radial passageway 108 to said chamber 68.

The length of the longitudinal groove 110 is selected so that when the spray head 36 first is stroked downward, and the valve seat of rim 86 is unseated, pressurized fluid will flow only through the groove 110 to the interior of the meter- ing chamber 68 until the stroke travels the distance "y".

Continued depression of the spray head 36 equal to the distance 1 10 "x" results in the roove 4Φ8 bein blocked off from the i metering chamber 52 by the stem outer wall at 111 immediately above the upper end of longitudinal groove 110. At this point in the downs roke cycle, the metering chamber 68 is isolated. The downward stroke of the spray head 36 is con-tinued to terminate when the radial passageway 108 has traversed an axial distance greater than the distance "x". At this point, the passageway 108 now is disposed below the upper gasket 46. Thus, only the charge of product previously captured within the metering chamber 68 is discharged to the bore 100, which functions as an expansion chamber, thence to the passages 102 and 104 to the dispensing orifice 106.

Now, as the spray head 36 is released, pressurized product once again passes along through the longitudinal groove 110 into the interior of the metering chamber 68 at least partially to fill same. Thus, filling of the meter-ing chamber 68 occurs during both the downstroke and the return or upstroke of the spray head 36 and depending stem 98.

As can be understood from the above, preferably the length of the longitudinal groove is such as to enable the upper end to open to the metering chamber 68 when the stem is engaged bottomed in socket 82 with the valve plunger 70, and particularly, its valve seat in normal sealing engagement with the undersurface of the lower gasket 58. As ex-plained above, when the spray head 36 is depressed first, the valve plunger is forced against the spring 72 to unseat the plunger and permit pressurized product to pass over the rim 86 into the groove 110 and thence to fill the metering chamber 68.

The so-called two-stage or downstroke-upstroke filling of the metering chamber provided by the valve assembly according to the invention ensures that the said chamber always is filled to its capacity before any pressurized product is dispensed.

When continuous rather than intermittent dosage spray is desired, one merely removes the spray head 36 and its depending stem 98 from engagement within the socket 82 -without .any dispensing or waste occurring but for the quantity of material found within the metering chamber 68, which is minor. Then, another spray head and hollow depending stem can be substituted, the stem having a length common with that of stem 98 but carrying a through slot formed in the lower wall thereof in lieu of the groove 110 of stem 98.

Removal, cleaning and replacement of spray head 36 is adequate for clearing and cleaning of both hole 108 and groove 110. Since there is a filling of the metering cham- 68 ber=£8 both on upstroke and downstroke, the metering chamber 68 is always filled, and accordingly, accumulation of debris or hardened product within the metering chamber is materially inhibited. Accordingly, the full capacity of the metering chamber is maintained available throughout the useful life of the pressurized package 20 incorporating the Figures 3-5 illustrate the operation of the invention.

In Figure 3, the spray head 36 is illustrated as first partially depressed to enable product to pass along the path indicated by arrows 112, over the rim 86, into the longitudinal groove 110 and then into the metering chamber 68. The radial passageway 108 of stem 98 is exterior of the boss 38, or, at most, is disposed within the perforation of gasket 46. Thus radial passageway 108 does not communicate with chamber 68 at this stage in the valve's operation. This condition will ensue for depression of the spray head 36 through a distance equal to "y" (Figure 2).

In Figure 4, the valve assembly is illustrated in the condition assumed when the spray head 36 has reached an intermediate stage in its downstroke. The spray head 36 has been depressed a distance equal to "x" (Figure 2). Passage of pressurized product through the radial passageway 108 and through the groove 110 is blocked, notwithstanding the un-seated condition of the valve plunger. The radial passageway 108 is shielded by engagement with the gasket 46 while the stem wall is engaged with gasket 58 at 111 to block passage of fluid from the groove 110 into the metering chamber 68 isolating same. .

In Figure 5, the valve assembly is illustrated in the condition assumed for dispensing the capacity of the indicated by arrows 114. The circumferential wall of the stem immediately above the longitudinal groove 110 remains engaged with the gasket 58 and thus blocks passage of product from the valve chamber 54 to the metering chamber 68. The radial passageway 108 is exposed to the interior of the metering chamber 68 and fluid is permitted to pass through said passageway 108. On release of the spray head 36 from its fully depressed condition, the valve assembly returns to the condition shown in Figure 3 until the rim 86 once again is engaged with the gasket 58.

In Figure 6, the valve assembly according to the invention is illustrated in the condition assumed upon pressure filling with product subsequent to the assembly of the valve housing 32 and attendant parts upon the assembled cylinder 22, dome 24 and cover 28. An injector head 116 of known construction and leading from a source 118 of pressurized product (shown diagrammatically) is inserted through opening 50 to engage the gasket 46 sealingly through perforation thereof. Pressurized product is then released through openings 120 in the injector head 116 into the metering chamber 68 and through opening 66 and the perforation in gasket 58. Said product overcomes the bias of spring 72 to dislodge the valve plunger 70 whereby pressurized product enters the valve chamber 54 and the interior of the package 20 through the dip tube 34. The flow path taken by the pressurized product is indicated by arrows 122. ϊη Figure 7, there is shown a typical insert 60 used to define the metering chamber 68. This insert 60 preferably is a plastic molded member having a cylindrical body 124, a tapered floor 64 and a central opening 66 formed in said floor. The annular rim 62 thereof is imperforate and uniform. The chamber 68 defined interior of the body 124 is of predetermined capacity and can be changed by change in the dimensions thereof.

Thus, in summary, the structure provided by the inven-tion provides the following and more specific technical advantages over prior "dosage" valve structures by providing a metering or dosage valve assembly: which can be cleared, if clogged, by removal, cleaning and replacement of a spray head associated therewith; which includes, as metering chamber defining means, a cup-like insert member separately fabricated and assembled as a part of the valve assembly which has a predetermined interior capacity so that the charge to be dispensed on each actuation of the spray head can be changed without variation in the other valve components by substitution of a like insert having a different capacity; which includes a metering chamber filled during both the downstroke and return stroke of the spray head, thereby assuring complete fill and dispensation; which is easily fabricated without complex molds and machinery; which is adapted for pressure filling procedures; which is provided with a separate Valve plunger having a socket to receive a hollow stem, the socket having an annular gallery surrounded by an annular rim functioning as a valve seat, instant response being effected to fill the metering chamber when the rim is unseated; and which has a removable and replaceable spray head and depending hollow stem, the stem carrying a radial passageway in the wall thereof at the upper end and axially extending longitudinal groove in the wall at the lower end and opening radially outwardly thereof, the groove forming the only path for product to enter the metering chamber and the radial passageway forming the only path for product to leave the metering chamber, thereby affording access to the two most critical areas of the valve assembly for clearing thereof if clogging should occur.

Claims (16)

CL A I M S 8

1. , A valve assembly for aerosol spray packages or the like for dispensing premeasured dosages of product contained therein wherein the valve assembly includes a cover member to be secured to the package, a hollow housing secured to the cover member and when mounted communicating to the interior of the package, a normally isolated metering chamber of predetermined volume disposed within the housing for establishing said dosage., and having entry and outlet communicatin to the package interior and the atmosphere respectively, perforated gasket means at the said entry and outlet, spring-biased valve plunger reciprocable within the housing vith its valve seat normally engaged to block entry to the metering chamber, a removable spray head having a depending hollow stem engaged sealingly slidably through said perforated gasket means terminating in a socket formed in the valve plunger and normally blocking communication vith said metering chamber, passage defining means comprising a longitudinal groove and a through radial passageway said longitudinal groove being formed in the outer circumferential wall of the stem at the lover end thereof and said through radial passageway being formed in the stem wall at a location disposed exterior and above the valve cover when the valve plunger is in its normal condition and said stem being adapted to be stroked downward upon depressing of said spray head first only to unseat the valve plunger, filling the metering chamber, said stem stroke continuing downward again to isolate the metering chamber and said stem stroke further continuing to establish the connection of the radial passageway only to the metering chamber for purging of contents thereof and at least partial refilling of said chamber effected upon return movement of said sprayhead*

2. The valve assembly according to claim 1 wherein the metering chamber is defined by a cup-like insert disposed in the valve housing, the cup having a rim and floor provided with an axial opening, the gaskets being disposed at the rim and adjacent the axial floor opening*

3. » The valve assembly according to claim 1 wherein the stem has its lower end engaged with the valve plunger in its normal condition with only its groove communicating to the metering chamber and the radial passageway communicating only to the atmosphere*

4. · The valve assembly according to claim 1 wherein the relative location of the radial passageway and the upper portion of the longitudinal groove is selected so that flow of products into the metering chamber through the groove on unseating of the valve plunger is effected without changing the normal condition of the radial passageway, and that continued movement of the spray head in the downward stroke thereof moves the groove out of communication with the metering chamber notwithstanding the unseated condition of the valve plunger but without connecting the radial passageway to said metering chamber.

5. The valve assembly according to claim 1 wherein the return stroke of the spray head places the groove in communication with the metering chamber until the valve plunger is reseated in normal condition after isolating the radial passageway therefrom and thereby being effective at least partially to refill the metering chamber.

6. The valve assembly according to claim 1 wherein the radial passageway is located spaced from the upper end of the longitudinal groove a distance sufficient to establish communication between the said radial paseageway and the metering chamber only when the upper end of the longitudinal groove is isolated from said metering chamber.

7. The valve assembly according to claim 1 wherein the length of the stroke required to place the radial passageway in communication with the metering chamber is greater than the length of the stroke required to isolate the metering chamber from the groove once the valve plunger is unseated. »1

8. The valve assembly according to any one of claims 1, and 3 to 7 wherein said stem is bottomed within said socket.

9. The valve assembly according to any one of claims 1 and 3 to 7 wherein an annular pocket is formed between the valve seat and the socket bottom, and said groove opens to the pocket.

10. The valve assembly according to any one of claims 1 and 3 to 7 wherein the metering chamber comprises a oup-like member of predetermined interior volume and having an upper annular rim engaged with the first gasket and a central floor passageway opening to the second gasket and co-axial with the perforation thereof. i

11. The valve assembly according to any one of claims 1 and 3 to 7 in which the perforated gaskets are co-axially disposed .

12. A pressurized package comprising a canister containing pressurized product and a valve assembly for dispensing metered amount of pressurized product from the canister, said valve assembly comprising a cover mounted to the canister, a tubular valve housing mounted to the cover, said housing including an upper chamber and a ported lower chamber, a pair of perforated gaskets spaced apart at opposite ends of said upper chamber, an upwardly opening cup-like member disposed tightly within said upper chamber between said gasketB, a valve plunger reciprocably arranged within said lower chamber, a spring normally biasing said, valve plunger into seated engagement against the undersurface of the lower one of said gaskets, said cup-like member defining a metering chamber of predetermined, capacity, and a removable spray head having a depending hollow stem, said stem having a radial passageway at its upper end and an outer longitudinal groove at its lower end, said stem being engaged, slidably sealingly through said gaskets and coupled to said valve plunger, the radial passageway normally located exterior of the valve cover and the longitudinal groove communicating with the metering chamber, the spray head and stem adapted to be stroked downward to initially unseat the valve plunger to enable pressurized product to enter the metering chamber only through the groove without exposing the radial passageway to said chamber, thereafter to isolate the metering chamber, and lastly to connect the radial passageway to the metering chamber from the valve chamber whereby to dispense the full capacity of the metering chamber, the release of the spray head again isolating the inerior of the stem from the valve chamber while permitting entry of pressurised product from the lower valve chamber into the metering chamber until the valve plunger is seated against the lower gasket.

13. A valve assembly for dispensing a metered amount of a pressurized product, contained in a canister to which said valve assembly is mounted, during a single stroke cycle of spray head associated with said valve assembly and said valve assembly comprising : a. a cover member adapted for securement to a canister; b. a hollow housing secured to said cover member and having a port at the bottom end thereof for establishing communication with the interior of the canister when the cover member is mounted thereon; c. a first perforated gasket disposed between the housing, and the cover member; d. a second perforated gasket disposed within the housing spaced from the first perforated gasket and coaxial therewith; e. means defining a metering chamber of predetermined volume in the housing and between said gaskets; f. a spring-pressed valve plunger mounted in the housing between said port and said second gasket and normally seated against the bottom thereof, isolating said metering chamber blockin the movement of pressurized product between the metering chamber and said port; g. a removable spray head having a depending hollow stem slidably sealingly engaged through said perforated gaskets and engaging said valve plunger and the stem including: i . a radial passageway through a wall thereof at the upper end; and ii. an axially extending longitudinal groove in the exterior surface of said stem wall, adjacent the bottom thereof and opening radially outwardly of said stem; and h. said stem normally having its lower end engaged with the valve plunger with only its groove communicating with the metering chamber and with said radial passageway communicating only with the atmosphere, flow of pressurized product between the said port and the metering chamber being possible only by way of said groove and said pressurized product being blocked from entering said groove by the seated condition of said valve plunger and i, said stem adapted to be stroked downward upon depression of said spray head first only to unseat the valve plunger, filling the metering chamber, said stem stroke continuing downward again to isolate the metering chamber and said stem stroke further continuing to establish the connection of the radial passageway only to the metering chamber for purging of the contents thereof.

14.. A valve assembly for dispensing a metered amount of a pressurized product contained in a canister to which said valve assembly is mounted during a single stroke cycle of a spray head associated with said valve assembly, Bald valve assembly comprising, a cover member adapted for securement to a canister, a hollow housing secured to the cover member and having a port at the bottom end thereof for establishing communication with the interior of the canister when a cover member is mounted thereon, a first gasket having a central opening and disposed between the cover member and the housing, a second gasket having a central opening coaxial with the first gasket opening and arranged within the housing spaced from said first gasket, means defining a metering chamber seated within the housing between the first and second gasket¾ blocking means in the housing and disposed below the second gasket normally to isolate the metering chamber from said port, a removable spray head having a depending hollow stem slidably seallngly engaged through said gasket openings, said stem having a radial passageway through a wall thereof near the stem upper end and a longitudinal groove in the stem wall at the stem lower end, said longitudinal groove opening radially outward from said wall, said spray head and stem operably engaged with said blocking means to effect a normal condition isolating the metering chamber from both said port and the radial passageway, said spray head and stem adapted to be stroked downward to a first condition unseating said blocking means exposing said groove to pressurized product without exposing the radial passageway to the metering chamber whereby pressurized product is permitted to flow from said port only through said groove into said metering chamber to fill same, the downward stroke continuing to a second condition whereat the metering chamber is again isolated from both said groove and radial passageway and further continuing through to a final condition establishing communication between the radial passageway and the metering chamber to purge same while the metering chamber is maintained Isolated from communication with the groove, said spray head and stem being returnable to the normal condition aforementioned through said conditions to enable at least partial refilling of the metering chamber prior to reseating of the valve plunger.

15. A valve assembly for dispensing metered amounts of pressurized product contained in a canister to which the valve assembly Is mounted and during a single stroke cycle a spray head associated with said valve assembly, said valve assembly comprising a removable spray head having a dispensing orifice and an Integral hollow depending stem communicating thereto, a radial passageway formed in the wall of said stem at the upper portion thereof and an axially extending longitudinal groove formed in the stem wall opening radially outward therefrom, the upper end of said groove bein spaced a predetermined axial distance from said radial passageway toward the lower end of the stem, a valve cover having a central perforated boss and adapted for securement to the canister, a valve housing seated within said boss and having a port opening to the Interior of the canister when the cover member is mounted thereon, a first centrally perforated gasket disposed between the valve cover and the housing coaxial with said boss, a second centrally perforated gasket arranged within said housing spaced from the first gasket and coaxial therewith, means seated within said housing and between said gaskets defining a metering chamber of predefined volume, a spring-pressed valve plunger arranged for vertical reciprocation within said housing between said port and said second gasket and normally engaged seated against the said second gasket isolating said metering chamber from said port, said stem being slidably, sealingly engaged through both gaskets with the lower end thereof operatively coupled to the valve plunger and only the said groove communicating to said metering chamber, spra head and stem adapted to be stroked downward initially to unseat the valve plunger permitting pressurized product to pass through said groove into the metering chamber, further continuing downward stroke of the spray head and stem disposing the upper end of said groove within said second gasket to block flow of pressurized product into the metering chamber and the downward stroke continuing to brin the radial passage only disposed in communicating relation with the metering chamber for purging of the contents thereof the dispensing orifice, release of said spray head and stem reestablishing communication between said port and said metering chamber until the valve plunger is reseated, thereby at least partially to refill said metering chamber.

16. The valve assembly substantially as described in the foregoing specification with reference to the accompanying drawings.