Abstract:
A hand-held, pneumatically propelled, metering dispenser for powdered or granular products such as pesticides, the dispenser having a manually operated pneumatic pump, a product canister, a metering scoop insertable into the product canister in operative alignment with the pneumatic pump, and a discharge line into and through which powder or granules supported in the scoop are blown by operation of the pneumatic pump.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates to pneumatic dispensers for compositions in powder or granular form such as, for example, powdered and granular pesticides. More particularly, the invention relates to a hand-held, metering dispenser that will enable the user to carefully control the amount of powder or granules applied at each use site. 
     2. Description of Related Art 
     Insects such as ants, crickets and roaches often travel and dwell in areas that are difficult to access, such as the backs of cabinets, and cracks and crevices in wood and concrete structures. A bait product that is deposited in these areas is more effective than baits placed in areas that are well lighted and generally more accessible because such areas are typically frequented by insects only at night. 
     It is often desired to put a known amount of powder or granule material in hard-to-reach areas. Holes can be drilled in walls, and powder or granule products can then be blown into the walls through the holes. The powder or granule materials can be dispensed by a variety of hand pumps, many using manual or automated pneumatic delivery systems. Liquids can also be pumped into blind areas using many of such devices, but can do serious damage to drywall if over-applied. Also, it is generally known in the trade that a dry granule bit can remain active for a longer period of time than gels or liquids since the moisture tends to break down the stability of the materials. 
     The use of hand-held pneumatic sprayers for applying liquid or powder pesticides is well known. One such hand-held powder sprayer is disclosed, for example, in U.S. Pat. No. 4,225,065. Such sprayers typically have a chamber or canister that is first loaded with a quantity of the material to be sprayed. The material is then dispensed by manually reciprocating a pneumatic plunger that forces air through the chamber or canister, entraining some of the material to be dispensed and discharging it through an outlet port or spray nozzle. One disadvantage of the known hand-held devices is the difficulty encountered by the user in monitoring the amount of material being applied at each use site. This can be particularly difficult where the sprayer is used to force powder or granules through a small opening into an enclosed structure, such as a wall, or other blind area where the user cannot physically observe the amount of product being dispensed. Although, with the prior art devices, the amount of material dispensed is generally proportional to the number of times the plunger is reciprocated, a device is needed that will enable the user to more reliably monitor the amount dispensed. This is particularly important where the sprayer is used commercially, where the material being sprayed is relatively expensive, and where over-spraying produces no corresponding resultant improvement. 
     A hand-held powder sprayer is therefore needed that is inexpensive and easy to use, but that preferably includes a simple and reliable, internal metering device that can be used to control the amount of powder being dispensed through the sprayer. 
     Other prior art pneumatic and aerosol-powered pesticide dusters useful for dispensing powders into wall structures or other blind areas are disclosed, for example, in U.S. Pat. Nos. 4,553,698; 4,648,202; 4,823,505; 5,058,312; 5,309,669 and 5,361,533. 
     Powder sprayers with pneumatic powder supply systems preferred for use with printing presses are disclosed, for example, in U.S. Pat. Nos. 5,083,710, 5,213,271 and 5,746,131. Powder sprayers using electrostatic charging technology are disclosed, for example, in U.S. Pat. Nos. 4,399,945 and U.S. Pat. No. 4,966,330. 
     SUMMARY OF THE INVENTION 
     According to a preferred embodiment of the invention, a hand-held, pneumatic metering dispenser is provided that is useful for propelling predetermined quantities of particulate materials such as powder and granules from a canister, through a discharge conduit and toward a target. The apparatus of the invention is particularly useful for spraying known quantities of powdered and granulated pesticide products into walls or other blind structures or locations. 
     The preferred apparatus of the invention is a hand-held applicator for powder and granules comprising a pneumatic pump, a product canister and a metering scoop insertable into the canister that communicates with a product discharge tube. Once a supply of powder or granular material is loaded into the canister and the metering scoop is installed, a predetermined quantity of the powder or granules is loaded into the scoop simply by rotating the applicator 360° around its longitudinal axis. The filled metering scoop is most preferably positioned inside the canister in an upwardly facing position near the top of the cylindrical sidewall. When pressurized air is expelled into the canister from the pneumatic pump, the increased pressure inside the canister forces the predetermined quantity of powder or granular material from the scoop through an orifice disposed in its bottom wall, and into and through the discharge line of the applicator. 
     The apparatus of the invention can be marketed and used as a new device or as a modification to existing “off-the-shelf” sprayers by simply replacing the original discharge assembly. This invention can be also be used in an application where one product is need to be measured and dispensed along with a lighter or heavier weight product, although it is believed that most of the more common applications will involve dispensing a dry product in a stream of air. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The apparatus of the invention is further described and explained in relation to the following figures of the drawings wherein: 
     FIG. 1 is a perspective view of a preferred embodiment of the metering dispenser of the invention; 
     FIG. 2 is an enlarged cross-sectional view taken along line  2 — 2  of FIG. 1; 
     FIG. 3 is an exploded perspective view of the forward portion of the metering dispenser of FIG. 1, showing the metering scoop and discharge conduit prior to assembly with the canister; and 
     FIG. 4 is an enlarged cross-sectional view taken along line  4 — 4  of FIG.  1 . 
     Like reference numerals are used to indicate like parts in all figures of the drawings. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring to FIGS. 1-4, metering dispenser  10  of the invention preferably comprises pneumatic pump assembly  12 , canister assembly  14  and discharge assembly  16 . Pneumatic pump assembly  12  preferably further comprises elongated cylinder  18  having rod  20  and plunger  24  slidably insertable therein. Handle  22  is manipulated by the user to reciprocate rod  20  and plunger  24  inside cylinder  18  to force air into canister assembly  14  as discussed below. Orifice  26  as shown in FIG. 1 is preferably a conventional check valve of the type used in pneumatic sprayers and bicycle air pumps. 
     Referring to FIGS. 1 and 4, canister assembly  14  preferably comprises a cylindrical canister  40  that is attachable in coaxial alignment with pneumatic pump assembly  12 , end wall  48  having opening  47  with externally threaded collar  50 , and valve  54  in end wall  55 . Referring to FIG. 4, valve  54  is preferably disposed in end wall  55  of canister  40  adjacent to cylinder  18  so that air compressed by the forward movement of reciprocating plunger  24  of pump assembly  12  as seen in FIG. 1 is forced into the interior of canister  40 . Cylinder  18 , valve  54  and canister  40  are preferably attached in fixed relation to each other by any suitable means such as, for example, by the use of threads, by welding, brazing, or the like. End wall  48  of canister  40  preferably comprises opening  47  that is large enough to facilitate loading powder or granular material into canister  40  prior to use. Annular collar  50 , preferably having external threads, is provided for use in releasably attaching discharge assembly  16  to canister assembly  14 . 
     Discharge assembly  16  preferably comprises discharge tube  34 , internally threaded coupling  28  having a forwardly extending conical portion  32  attached in fixed relation to discharge tube  34 , metering scoop  44  attached in fixed relation to discharge tube  34 , and tubular extension member  36  having open end  38  for discharging powder from dispenser  10 . The portion of discharge tube  34  passing through conical portion  32  of coupling  28  is preferably coaxially aligned with pump rod  20 . Tubular extension member  36  can be made of metal, plastic or other polymeric material as desired. 
     Referring to FIGS. 2-4, metering scoop  44  is preferably made of metal or plastic in the shape of a tapered trough comprising proximal and distal end walls  66 ,  68 , respectively, connected to U-shaped bottom and side wall  45 . The bottom portion of wall  45  is preferably upwardly tapered between proximal end wall  66  and distal end wall  68 . For reasons explained in greater detail below, leading side edge  58  of wall  45  is slightly lower than trailing side edge  60 . The top of metering scoop  44  is open over most of its length, except for a covered section  62  disposed over outlet port  52 , located in the bottom of wall  45  adjacent proximal end wall  66 , where discharge tube  34  is connected to scoop  44 . Covered section  62  prevents powder that is lifted or entrained by the air flow from being carried over the walls of scoop  44  and falling back into canister  40 . Covered section  62  preferably does not cover more than about one third the length of scoop  44  and, most preferably, from about one fourth to about one third the length of scoop  44 . Discharge tube  34  is desirably formed with an outwardly turned bend or curvature at the end, and is attached to metering scoop  44  so as to provide an open flow path between the interior of scoop  44  and the interior of discharge tube  34  through orifice  52 . Because discharge tube  34  is desirably curved or bent, metering scoop  44  is offset from, but still substantially parallel to, the central longitudinal axis extending through canister  40 . It should be appreciated that FIGS. 2 and 4 are not drawn to scale, and according to a particularly preferred embodiment of the invention, the radial clearance between scoop  44  and canister  14  ranges from about one-eighth to about one-half inch, and most preferably, from about one-eighth to about one-fourth inch. 
     The size of metering scoop  44 , the shape and diameter of discharge tube  34  and the diameter of opening  47  are all cooperatively sized to permit the insertion of scoop  44  through opening  47  into canister  40  during assembly of dispenser  10 . The diameter of orifice  52  and the inside diameter of discharge tube  34  are preferably sufficiently large that they will freely accommodate the passage of the powder or granular material through them, yet small enough that the pressure exerted will be sufficient to propel the powder or granules from scoop  44 , into and through discharge tube  34  and optional extension member  36 . According to a particularly preferred embodiment of the invention, the exterior of dispenser  10  will bear a label at some location that informs the user as to the internal volume of metering scoop  44 . 
     Referring to FIGS. 1,  2  and  3 , coupling  28  of discharge assembly  16  is preferably made with an outwardly visible index mark  30  located at the position on the circumference of coupling  28  that indicates the position of metering scoop  44  relative to coupling  28  whenever metering scoop  44  is inserted into canister  40  and coupling  28  is threaded onto collar  50 . When dispenser  10  is assembled with coupling  28  fully threaded onto collar  50  of canister assembly  14 , and index mark  30  is facing upwards (FIG.  1 ), the user will know that metering scoop  44  is in the “12 o&#39;clock” position, with its open top facing upwardly. This feature of the invention, or the substitution of another similarly effective indicator, is significant so that the user will know when metering scoop  44  is “loaded” with powder or granules and ready for the application of pneumatic pressure to canister  40 . 
     Use of the invention is further described and explained in relation to FIGS. 1-4. Prior to attachment of discharge assembly  16  to canister assembly  14 , a quantity of the powder or granular material to be dispensed is poured into canister  40  through opening  47 . Preferably, canister  40  is filled not more than about three-fourths full. Coupling  28  is then threaded snugly onto collar  50 , following which metering dispenser  10  is ready for use. To operate dispenser  10 , the user grasps the unit and rotates it in either direction around its longitudinal axis until index mark  30  is facing upwardly, in which position metering scoop  44  is also facing upwardly. The user then rotates the dispenser around its longitudinal axis in the direction shown by arrow  46  in FIGS. 1 and 2 until mark  30  again appears on top of coupling  28 . 
     As dispenser  10  is rotated in the counter-clockwise direction demonstrated by arrow  46 , the offset of scoop  44  relative to the central longitudinal axis of dispenser  10  causes metering scoop  44  to sweep through the bed of powder or granules contained in canister  40 , which remain in the lower portion of canister  40  as it is rotated. As metering scoop  44  is rotated through the bed of powder or granules  42 , the height differential between leading edge  58  and trailing edge  60  causes scoop  44  to fill. The slightly higher trailing edge  60  of metering scoop  44  also causes it to retain the powder or granular material  42  as scoop  44  emerges from the bed of loose powder and rotates upwardly to a vertical position. When scoop  44  is loaded and at the position shown in FIGS. 2 and 4, it is filled with powder or granules  42 . As the user reciprocates handle  22 , rod  20  and plunger  24  inside cylinder  18 , while maintaining dispenser  10  in substantially the same rotational alignment, air blown into canister  40  through valve  54  pressurizes the interior of canister  40  to a level sufficient to apply a force as indicated, for example, by arrow  64  (FIG. 4) to cause powder or granular material  42  inside metering scoop  44  to descend through orifice  52  and into and through discharge line  34 . The powder or granules  42  are then discharged under pressure through open end  38  of extension member  36  (or directly from discharge tube  34  if no extension member  36  is used). 
     Depending upon the volume and pressure of the air forced into canister  40  from pump assembly  12 , and depending upon the volume and density of the powder or granules  42  being dispensed, more than one pump stroke may be necessary to apply the total amount of product in metering scoop  44 . Provided, however, that dispenser  10  is neither shaken nor rotated again so that metering scoop  44  travels through the underlying bed of powder or granules  42 , the user will know the volume of powder or granules  42  dispensed. When the amount of powder or granules  42  inside canister  40  is such that the surface level inside canister  40  is above valve  54 , air expelled into canister  40  through valve  54  will still migrate upwardly through the powder or granules, pressurizing the interior of canister  40  sufficiently to cause powder or granules  42  to flow from scoop  44  into discharge line  34 . Because of the proximity of the open top of metering scoop  44  to the cylindrical side wall of canister  40  during use of dispenser  10  to apply powder or granules  42 , no appreciable amount of powder or granules will be entrained and carried up from the bed into metering scoop  44  by the air flow inside canister  40 . 
     Although the size and shape of metering scoop  44  can vary, the volume of powder or granules that the scoop can hold should not exceed the smallest amount that the user is likely to want dispensed at a particular location. A metering scoop  44  having a volume sufficient to hold from about 3 to about 5 grams of a particulate pesticide is preferred, although it will be appreciated that the weight of the material that can be supported inside scoop  44  will necessarily vary according to the density of the material. If desired, discharge assemblies  16  having metering scoops  44  with different volumes can be provided for use with various powdered or granular materials. Alternatively, discharge assemblies  16  can be made in such manner that metering scoops  44  of different volumes can be selectively attached to discharge tube  34  in order to accommodate different materials as desired. 
     Other alterations and modifications of the invention will likewise become apparent to those of ordinary skill in the art upon reading the present disclosure, and it is intended that the scope of the invention disclosed herein be limited only by the broadest interpretation of the appended claims to which the inventor is legally entitled.