US3239717A

US3239717A - Method and apparatus for dispersing glomerate particles

Info

Publication number: US3239717A
Application number: US175458A
Authority: US
Inventors: Carl R Peterson
Original assignee: Goodrich High Voltage Astronautics Inc
Current assignee: Goodrich High Voltage Astronautics Inc
Priority date: 1962-02-26
Filing date: 1962-02-26
Publication date: 1966-03-08
Anticipated expiration: 1983-03-08

Description

March 8, 1966 c. R. PETERSON 3,239,717

METHOD AND APPARATUS FOR DISPERSiNG GLOMERAIE PARTICLES Filed Feb. 26, 1962 United States Patent 0 3,239,717 METHOD AND APPARATUS FOR DISPERSIN G GLOMERATE PARTICLES Carl R. Peterson, Lexington, Mass, assignor to Goodrich- High Voltage Astronautics, Inc., Burlington, Mass, a corporation of Delaware Filed Feb. 26, 1962, Ser. No. 175,458 6 Claims. (Cl. 3173) This invention relates to the generation of a dispersive spray from a powdered substance, and to the breaking up of the agglomerated groups into which the consitituent particles of such a powdered substance tend to form. More particularly, it comprehends inserting an electrically conductive or semi-conductive powdered substance between two electrostatically charged plate members Wherein the particles are successively attracted from one plate member to the other. The continuing series of impacts as the particles impinge first on one plate member and then on the other eifectively break up any agglomerated groups existing in the powdered substance. The oscillating particles are then concentrated at the center of the plate members by the slightly inclining adjacent surfaces thereof, and an apertures centrally disposed in one of said plate members provides means for ejecting a spray of such particles.

The principles of my invention are applicable to any type of dust feed apparatus and will find extensive use especially in instances where the powdered particles are small, three microns and less, and where good density uniformity is required. Many chemical applications, as well as colloid propulsion devices and the like are typical examples. A more specific example of the utility of such a device is that of dry substance spray printing. In a system for automatically sorting letters in accordance with certain symbols marked thereon, it is required that such symbols be put on the letters without the use of pressure. Also, since the sorting machine pick up apparatus is responsive to light, and read out is relatively critical, it is important that the consistency of the symbol be uniform. The present invention discloses apparatus that is adapted to effectively meet these requirements. In combination with a proper stencil any symbol may be uniformly sprayed on a letter regardless of the surface texture or thickness thereof. The reliability and uniformity of symbols marked by such a dry spray stenciling procedure, then, make it preferable to stamping or liquid spray techniques.

The state of the art prior to my invention is reflected by devices which mechanically agitate the particles and eject the desired spray by means of an aspirator nozzle. Mechanical agitation of dust or powder comprised of particles of three microns or less is particularly ineffective, and it is in this range that my invention finds its widest application. Another current method of providing a powdered spray comprehends dispersing a finely divided solid by means of gas under pressure. This method, of course, does not solve the agglomeration problem and therefore does not produce a spray of uniform density.

Accordingly, it is a principal object of my invention to provide a new and improved method for dispersing, in a finely divided powder substance, the glomerate particles that form therein.

It is another object of my invention to provide novel dust feed apparatus adapted to generate a spray of finely divided particles, said spray having better density uniformity than has heretofore been obtained by like devices.

It is still another object of my invention to provide electrostatic means for breaking up the glomerate particle groups into which a finely divided powder substance tends to form.

It is yet another object of my invention to provide apparatus of the type described whereby a powdered substance consisting of particles of less than three microns may be effectively de-agglomerated and ejected in the form of a spray or jet.

These, together with other objects and advantages of my invention will become more apparent from an examination of the following detailed description of one pres ently preferred embodiment thereof taken in conjunction with the accompanying drawing wherein:

FIGURE 1 schematically represents the electrostatic plate members of my invention and their geometric relationship to certain particles oscillating therebetween; and,

FIGURE 2 is a sectional view of one illustrative embodiment of the apparatus of my invention.

In accordance with the principles of my invention electrically

conductive plate members

13 and 14 are arranged as illustrated in FIGURE 1. A voltage, preferably DC, is applied therebetween that is suflicicnt to provide a voltage gradient in the order of 10 kv./cm. at the center of said plate members. A supply of electrically conductive or semi-conductive powdered substance 6 is supplied between the plate members by a plunger 5.. The particles of powdered substance 6 tend to adhere together and form glomerate groups 16. The usual application of the present device comprehends a powdered substance whose constituent particles are of 3 microns or less. For the purpose of illustration, however, the particles of FIGURE 1 have been made disproportionally large. The dust particles and glomerate groups then, upon contact with plate member 14 become electrically charged to the same polarity as the plate member itself. That is, in the present illustration, they become initially positively charged. Because of the proximity of negatively charged plate member 13 and the voltage gradient between plates, the positively charged particles and glomerate groups are attracted from plate member 14 to plate member 13. Upon reaching plate member 13 the particles and glomerate groups lose their positive charge and become negatively charged. The process is then repeated and the particles and glomerate groups are attracted back to the positive plate. Because plate member 14 is inclined with respect to plate member 13, the particles as they travel from plate to plate continually move toward the center of the plates as indicated by arrows 17 and finally escape through aperture 10. The particles, as they impinge first off one plate member and then the other, do so with some force and after a number of such collisions all the glomerate groups are broken up into original particles. Consequently the spray, asv it issues from aperture 10 consists of individual particles 18.

Referring now to FIGURE 2, there is illustrated a sectional view of one presently preferred embodiment of my invention. The

plate members

13, 14 thereof are fabricated of electrically conductive material such as copper and have adjacent face sections 3, 4 arranged to cause particles oscillating therebetween to concentrate at aperture 10. This is done by grinding face section 4 to a recessed conic geometry, as illustrated, having its apex opposite aperture 10.

Annular ridges

11, 12 are provided to prevent the escape of excessive amounts of the powdered substance between the edges of

plate members

13, 14. Insulating member 7 maintains a sufiicient distance between plate members to prevent any discharge thereacross. A voltage sutficient to maintain operation of the device, in the present illustration 2500 kv., is supplied from voltage source 8. A supply of powdered substance 6 is provided by means of plunger 5. The significant dimensions of the present illustrative example are; the 2.5 inch diameter of face sections 3, 4; the .01 inch diameter of aperture 10; and the .2 inch distance between apex 15 and aperture 10. Such dimensions are not controlling,

3 however, and are cited merely to indicate relative proportions of the apparatus. Various factors such as size of particle, voltage, application of the spray, capacity of the apparatus, and whether or not the device is used in a vacuum, will, of course, determine the exact design and dimensions of any given device. Finally, the apparatus illustrated in FIGURE 2 is packaged in and insulated from a housing member (not shown).

There has thus been disclosed a novel method and apparatus whereby the several objects of my invention are accomplished. While specific structure has been described by Way of illustrating said invention, it is not intended that any limitation of scope or concept by implied therefrom, the full extent of the invention being defined in the appended claims.

I claim:

1. The method of breaking up a quantity of agglomer ated electrically conductive particles in a spray apparatus comprising the step of injecting said quantity of agglomerated electrically conductive particles between two electrostatically charged plates of opposite, D.C. polarity whereby the particles dwell between said plates and come in repeated contact with said plates alternately, such particles assuming, upon such contact, and electrostatic charge of the same polarity as that of the contacted plate so that they are repelled by said plates alternately upon contact therewith.

2. Apparatus for producing a disperive spray from a quantity of agglomerated electrically conductive particles comprising two electrostatically charged plate members spaced apart in condenser relationship, one of said plate members having an aperture therein, the adjacent surfaces of said plate members being inclined toward one another in such a manner as to deflect particles traversing the space therebetween through said aperture, and means for injecting between said plate members said quantity of agglomerated conductive particles.

3. Apparatus for producing a dispersive spray from a quantity of agglomerated electrically conductive particles comprising first and second metallic plate members, said first plate member having at least one plane surface and including an aperture centrally disposed therein, said second plate member having one recessed conic surface, said conic surface of said second plate member being proximate and adjacent to said plane surface of said first plate member, the apex of said conic surface being opposite said aperture, means for applying an electrical potential between said plate members, and means for injecting between said plate members said quantity of agglomerated conductive particles.

4. The method of claim 1 for breaking up a quantity of agglomerated electrically semi-conductive particles.

5. Apparatus as defined in claim 2 for producing a dispersive spray from a quantity of agglomerated electrically semi-conductive particles.

6. Apparatus as defined in claim 3 for producing a dispersive spray from a quantity of agglomerated electrically semi-conductive particles.

References Cited by the Examiner UNITED STATES PATENTS 1,475,995 12/1923 Heis et al. 317-262 1,832,096 11/1931 Chafiee et al. 3l7-262 2,628,785 2/1953 Fink 241-1 2,896,263 7/1959 Frederick et al. 317-262 XR SAMUEL BERNSTEIN, Primary Examiner.

Claims

1. THE METHOD OF BREAKING UP A QUANTITY O AGGLOMERATED ELECTRICALLY CONDUCTIVE PARTICLES IN A SPRAY APPARATUS COMPRISING THE STEP OF INJECTING SAID QUANTITY OF AGGLOMERATED ELECTRICALY CONDUCTIVE PARTICLES BETWEEN TWO ELECTROSTATICALLY CHARGED PLATED OF OPPOSITE, D.C. POLARITY WHEREBY THE PARTICLES DWELL BETWEEN SAID PLATES AND COME IN REPEATED CONTACT WITH SAID PLATES ALTERNATELY, SUCH PARTICLES ASSUMING UPON SUCH CONTACT, AND ELECTROSTATIC CHARGE OF THE SAME POLARITY AS THAT OF THE CONTACTED PLATE SO THAT THEY ARE REPELLED BY SAID PLATED ALTERNATELY UPON CONTACT THEREWITH.