Powder feed system

The present invention is directed to a vibratory powder feeding and metering apparatus that achieves the above-mentioned requirements. Generally, the apparatus of the present invention includes a housing defining a powder reservoir, a powder storage hopper having an outlet disposed to deliver powdered resin to the reservoir, a powder distribution block having one or more generally vertical fill tubes, a plurality of discharge ports extending from the reservoir to the fill tubes in the distribution block, and a vibration device to which the housing is mounted. Typically, the fill tubes are in communication with individual spray nozzles for transmission of the powdered resin. The housing also carries an adjustable barrier which serves as a dam to control or meter the flow of powdered resin into the discharge ports.

BACKGROUND OF THE INVENTION
 The present invention relates generally to powder conveying systems. More
 particularly, the present invention is directed to a powder feeding and
 metering apparatus for use in delivering powdered resin to a powdered
 resin spray nozzle. The invention finds particularly advantageous
 application in processes for applying powdered resin to fasteners.
 A variety of vibratory powder feed systems have been known in the art for
 many years. Such feeding systems, dating back to the 1950s and 1960s, have
 included both rotationally vibrated bowls and linearly vibrated channels
 or troughs.
 In the field of threaded fasteners, a need exists for feed systems useful
 for the application of powdered resins onto the fasteners. These resins,
 once applied, may serve any of several functions, including locking,
 sealing, lubrication or masking. Oftentimes the same feed apparatus will
 therefore be used with different resin powders, each having its own
 particle size distribution, specific gravity, coefficient of friction and
 perhaps other properties that affect its flow characteristics. Moreover,
 the same feed apparatus may be used with many different fastener sizes
 thereby requiring substantially different powder flow rates. Still
 further, the apparatus may be used with different spray assemblies, using
 one, two, three or even four spray nozzles.
 As a result a need exists for a simple, efficient vibratory feed apparatus
 that offers great versatility while still accurately feeding and metering
 the powdered resin for spray application to threaded fasteners.
 SUMMARY OF THE INVENTION
 The present invention is directed to a vibratory powder feeding and
 metering apparatus that achieves the above-mentioned requirements.
 Generally, the apparatus of the present invention includes a housing
 defining a powder reservoir, a powder storage hopper having an outlet
 disposed to deliver powdered resin to the reservoir, a powder distribution
 block having one or more generally vertical fill tubes, a plurality of
 discharge ports extending from the reservoir to the fill tubes in the
 distribution block, and a vibration device to which the housing is
 mounted. Typically, the fill tubes are in communication with individual
 spray nozzles for transmission of the powdered resin. The housing also
 carries an adjustable barrier which serves as a dam to control or meter
 the flow of powdered resin into the discharge ports.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
 As illustrated in the drawings, the powder feeding and metering apparatus
 of the present invention is designated generally as 10, and includes
 housing 12, storage or supply hopper 14, and distribution block 16. The
 housing 12 defines a powdered resin reservoir 18 having a generally
 horizontally oriented floor 20 between and walls 22 and 24. Extending
 through end wall 24 are a plurality of generally horizontally oriented
 discharge ports 26, each having an inner end 30 in communication with the
 reservoir 18 and an outer end 32. The housing 12 also supports a generally
 vertical and adjustable barrier 34 which together with the floor 20 of the
 housing defines a metering orifice through which the powdered resin flows.
 Alternatively, the barrier 34 may be disposed in direct abutment with
 floor 20 and may have one or more metering apertures to meter powder flow.
 Still other barriers with differently sized metering apertures or slots
 may also be used to vary the powder flow rate.
 The supply hopper 14 has an outlet 15 disposed to deliver powdered resin to
 reservoir 18. This form of powder delivery is conventionally known as a
 "flood fill" technique and has been used in powder transfer apparatus for
 many years. As is well known in the art, the powder level in the reservoir
 18 will be maintained at the level of the bottom of the outlet 15.
 The powder distribution block 16 is mounted to housing 12. Block 16
 includes a common passageway 42 and one or more powder fill tubes 44, each
 in communication with the passageway 42. The upper powder receiving end 45
 of each fill tube is supplied powdered resin exiting the outer ends 32 of
 the discharge ports 26. The lower powder distributing end 46 of the fill
 tube is in communication with the powder supply port of a conventional
 powder spray nozzle to deliver powder for application to a fastener. The
 distribution block is configured for a particular number of fill tubes and
 may be interchanged with other distribution blocks, such as blocks 17 and
 19, having different numbers of fill tubes as illustrated in FIGS. 3 and
 4. Thus, the apparatus of the present invention may be adapted for use
 with one, two, three, four or even more spray nozzles. The distribution
 block 40 also includes one or more breathe ports 48 which communicate with
 the common passageway 42. Many conventional spray nozzles in use today use
 a high pressure air supply to entrain the powder. These nozzles are known
 to create a negative pressure in the powder supply. In other words, the
 nozzle tends to aspirate powder from the powder feed system. Port 48
 insures that any aspiration effect caused by the spray nozzle will not act
 to increase the powder flow rate exiting the discharge ports.
 The housing 12 is mounted to any conventional linear vibration device 49
 well known to those of skill in the art. Typically, such vibrators
 includes frequency and/or amplitude controls allowing adjustment of the
 vibratory action.
 Since the accurate metering of the powdered resin to independent nozzles
 may be important in some applications, it is desirable to level housing
 floor 20 and the inner openings of the discharge ports 26 so that powder
 flow into each port 26 is approximately equal. To that end, a visual level
 indicator 50 is mounted to end wall 24 to facilitate leveling adjustments.
 For an alternative embodiment, a horizontal platform 52 may be mounted to
 barrier 34. This platform directs powder flow first toward wall 22, then
 down to floor 20 and then along floor 20 under barrier 34 into discharge
 ports 26. This arrangement has been found desirable for low volume flow
 rates.
 In accordance with the present invention, a wide range of powdered resin
 materials and flow rates can be accommodated. By adjustment of the
 vibration level, the powder height in the reservoir and the barrier
 metering aperture, the flow rate may be effectively controlled. Flow rates
 from about 0.15 grams per hour to as high as about 22.5 grams per hour may
 be achieved.
 Of course, it should be understood that various changes and modifications
 to the preferred embodiments described herein will be apparent to those
 skilled in the art. Such changes and modifications can be made without
 diminishing its attendant advantages. It is therefore intended that such
 changes and modifications be covered by the following claims.