the duster of the present invention comprises , briefly , a housing 11 providing a material hopper 12 and impeller and drive chambers 13 and 14 , here positioned on opposite sides of hopper 12 ; a closure plate 16 for drive chamber 14 ; a manually engageable crank 17 , journalled for rotation on plate 16 ; a gear train 18 in drive chamber 14 connected to crank 17 ; one of the improvements of the present invention comprising vent openings 21 and 22 formed in the base and side of the drive chamber for circulating cool air through the drive chamber and freeing it from pulverulent material entering therein . as will be best seen from fig4 plate 16 is formed with a bearing opening 23 , for the shaft 24 of crank 17 , and the side vent 22 for the chamber is provided by a plurality of circumferentially spaced openings 22 surrounding bearing 23 , see fig1 and 3 . as will also best be seen in fig4 housing 11 is formed with an interior wall 26 defining one side of hopper 12 and the interior side of drive chamber 14 , and which is normally positioned in a substantially vertical plane in the operation of the duster , and an integral annular , laterally - extending peripheral wall 27 surrounding the drive chamber and against which closure plate 16 is mounted to enclose the chamber ; and opening 21 is here formed in the normally bottom side 28 of peripheral wall 27 at the bottom of drive chamber 14 . accordingly , any of the garden dust finding its way into the drive chamber from hopper 12 may gravitate out of opening 21 . moreover , in the operation of the device , the whirling action of the gear train establishes an air current or flow through the chamber by way of openings 21 and 22 so as to constantly establish a stream of cooling air through the drive chamber and to move out any dust entering this critical operational area . the function of gear train 18 is to convert a comfortably fast rotation of crank 17 into a high - speed rotation of impeller 31 , positioned in chamber 13 . this is here accomplished by a shaft 32 , which connects the small terminal high - speed driven gear 33 of the gear train with the hub 34 of impeller 31 , shaft 32 here extending between chambers 13 and 14 straight across the bottom of the hopper 12 . vanes 36 are formed on shaft 32 in the hopper chamber for transporting the garden dust laterally through an opening 37 surrounding shaft 32 in an interior wall 38 dividing the hopper compartment from impeller chamber 13 so as to deliver the garden dust to the eye of impeller 31 . as a feature of the present construction , the major portions of the duster , including housing 11 , a lid 39 capping the hopper compartment 12 , crank 17 , shafts 24 and 32 , and all of the gears making up the gear train , are formed of plastic materials selected to provide necessary strength , anti - corrosion qualities , and being capable of injection molding . the critical working parts , including the gears , shafts and impellers , are preferably constructed of a composite plastic comprising glass - filled nylon ( about 10 % glass fiber ) and about 5 % polytetrafluoroethylene commonly sold under the trademark teflon . the housing and associated nonworking parts may be formed of polypropylene . one of the critical areas is the proper support of shaft 32 and its attached gear 33 for the stresses and high - speed operation to which these parts are subjected . it has been found that the required strength , durability , and low - friction support for shaft 32 may be obtained by journalling the shaft in a teflon bearing 41 mounted in interior wall 26 , see fig4 and 5 . another and important structural improvement of the present invention is the support provided for a pair of intermediate gears 42 and 43 , which are preferably molded as a one - piece construction and , in any event , connected for joint rotation on a common shaft 44 , gear 43 being enmeshed with and driving gear 33 , and gear 32 being enmeshed with and driven by gear 46 , carried by crank shaft 24 . as here best seen in fig4 shaft 44 is made of brass and is carried at its opposite ends in bearings 47 and 48 , formed in confronting relation on plate 16 and interior wall 26 . the journalling of brass shaft 44 in plastic bearings 47 and 48 provides an important improvement in strength , wear resistance , precision of operation , and low friction . the internal end of crank shaft 24 is preferably carried through wall 26 , see fig4 and is connected to the hub 51 of a dust - stirring member 52 , which is rotated by the crank within hopper chamber 12 for keeping the powder in a loose , flowable condition , it being noted from fig8 that the opposite end 53 of member 52 is journalled for rotation in an opening provided in interior wall 38 at the opposite side of the hopper chamber . another feature of the present invention is the provision of an improved support for the impeller 31 and means to prevent the accumulation and build - up of dust in the impeller chamber . although it is recommended that the apparatus be washed with water after each use so as to flush out dust , a failure to do so in the past has permitted a build - up of dust in the impeller chamber . many types of dust will absorb water and harden . a solid bridge may thus form across the bottom of the impeller chamber which will impact and break the impeller blades or vanes 56 , with the resultant failure of the device . with reference to fig6 - 8 , it will be noted that interior wall 38 partitioning the hopper and impeller chambers is formed with an integral , laterally - extending , peripheral wall 57 , and a plate 58 is mounted on wall 57 to enclose the impeller chamber and is , in turn , formed with a lateral wall 59 surrounding vanes 56 and providing a squirrel cage chamber 61 therefor , having a discharge passage 62 for the garden dust driven by the impeller . as an important feature of the present construction , peripheral wall 57 is formed with an opening 63 in the normally lower end 64 thereof , which effectively prevents the accumulation of material within and bridging the lower section of the squirrel cage chamber . plate 58 also provides an outboard bearing for shaft 32 and is formed with a plurality of circumferentially spaced openings 66 surrounding the axis of shaft 32 for admitting air into the impeller chamber at the base of vanes 56 for aerating the garden dust drawn through opening 37 and for admixing with and transporting the dust out of discharge opening 62 . the outboard bearing for shaft 32 has been another critical structural area causing premature failure of the present device . this problem has been solved by using a brass bearing 67 for the cylindrical outboard end 68 of shaft 32 . as here shown , bearing 67 comprises a brass sleeve , which is carried in a surrounding shoulder 69 formed on plate 58 and which positions the bearing in axial alignment with shaft 32 for receiving and journalling shaft end 68 . closure plates 16 and 58 may be secured in place by screws 71 threaded into bosses 72 formed on interior walls 26 and 38 . a handle 77 is mounted on the normally rear wall 73 of housing 11 for convenient manual support in one hand of the user while the other hand is engaged with crank 17 . a fitting 74 is mounted at the normally forward side 76 of housing 11 for receipt of one or more spray extension tubes ( not shown ).
a hand - held , manually - operated duster for propelling a controlled stream of pulverulent material , such as an insecticide dust , onto vegetables , roses , flowers , shrubs and small trees and the like and which comprises a unitary housing providing a material hopper and separate impeller and drive chambers , a rotary impeller being mounted in the impeller chamber and a hand crank and gear train being mounted in or associated with the drive chamber and connected to the impeller , powder being fed from the hopper to the impeller for discharge in a controlled stream .