Patent Publication Number: US-6209758-B1

Title: Powder feed system

Description:
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. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The novel features which are characteristic of the invention are set forth in the appended claims. The invention itself, however, together with further objects and attendant advantages thereof, will be best understood by reference to the following description taken in connection with the accompanying drawings, in which: 
     FIG. 1 is a side view of the powder feeding and metering apparatus of the present invention, also illustrating, in schematic fashion, the supply of powdered resin to a typical powder spray nozzle; 
     FIG. 2 is an end view of the apparatus of FIG. 1 having a powder distribution block used with a four nozzle application; and 
     FIGS. 3 and 4 are each end views showing distribution blocks used, respectively, with one and two nozzle applications. 
    
    
     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.