US2990807A

US2990807A - Apparatus for coating particles

Info

Publication number: US2990807A
Application number: US794596A
Authority: US
Inventors: Gordon P Gerow
Original assignee: Consolidated Vacuum Corp
Current assignee: Consolidated Vacuum Corp
Priority date: 1959-02-20
Filing date: 1959-02-20
Publication date: 1961-07-04
Anticipated expiration: 1978-07-04
Also published as: FR1248797A; BE587812A

Description

July 4, 1961 Filed Feb. 20, 1959 APPARATUS FOR GEROW 2,990,807 COATING PARTICLES 2 Sheets-Sheet 1 INVENTOR. Home P em/r W/ZA MM July 4, 1961 G. P. GEROW APPARATUS FOR COATING PARTICLES Filed Feb. 20, 1959 2 Sheets-Sheet 2 mg i? 96 J7 JIII/ .92 em J0 Z/AZMQ armegm United States Patent 2,990,807 APPARATUS FOR COATING PARTICLES Gordon P. Ger-ow, Athol, Mass, assignor, by mesne assignments, to Consolidated Vacuum Corporation, Rochester, N. Y., a corporation of New York Filed Feb. 20, 1959, Ser. No. 794,596 14 Claims. (Cl. 118-48) The present invention relates to apparatus for coating substrate and more particularly to an apparatus for coating small or finely divided particles.

Such apparatus is used extensively for coating particles such as glass flakes with a metal by thermally evaporating the metal and condensing the metal vapors in the glass flakes in a vacuum to produce glitter. Glass flakes and other small particles have been coated with a metal such as aluminum by dropping the particles past a source of metal vapors so that the metal vapors will condense on the individual particles as they fall past the coating source. This technique provides no control over the orientation of the particles when they are falling past the coating source. As a result only one side or an edge of a particle may be exposed to the coating source and thus receive a coating during a single coating operation. Also, it is extremely diificult to obtain a uniform distribution of the particles that are exposed to the coating source which may result in an inefficient utilization of the coating material or in an insufiicient coating on a portion of the particles falling past the source. A further disadvantage is that it is not possible to control the rate of descent of the particles when they are falling past the coating source. Thus the particles may not be exposed a sufi'lcient amount of time to the coating source to obtain a complete co-ating even on one side of the particles. These disadvantages of the prior art render it extremely difficult to obtain complete coatings on all of the particles or even a large percentage of the particles without dropping the particles past the coating source several times.

In accordance with the present invention an apparatus for coating small particles is provided which overcomes the above disadvantages.

The apparatus of this invention includes a source of coating material secured to a base and arranged to emit the coating material laterally from the source. Annular guide means are disposed laterally adjacent the source of coating material for guiding the particles in a downward path past the coating source at a predetermined rate and with uniform distribution so that all the particles are exposed a suflicient time to the coating source to insure complete coating of the particles. Means including the guide means are provided to turn the particles over at least once during their travel past the coating source to expose both sides of the particles to the coating material. Vibrating or impulsing means are coupled to the annular guide means at spaced points around the periphery for imparting impulses tothe guide means. A multi-phase source of power is coupled to the impulsing means so as to provide impulses which move around the periphery of the annular guide means in a manner similar to the movement of a rotating magnetic field, to uniformly distribute the particles on the annular guide means, whereby all of the particles Will be evenly coated with the coating material in one coating operation.

The invention is explained in reference to the drawings in which:

FIG. 1 is an elevation, partially in section, of an apparatus embodying the principles of the present invention;

FIG. 2 is a plan view of the apparatus of FIG. 1, and

FIG. 3 is a wiring diagramfor the solenoids used in the apparatus of FIG. 1.

Referring now to the drawing and particularly to FIG.

Patented July 4, 1961 1, a coating source indicated generally at 11 is disposed above a base 10. This coating source is specifically set forth and claimed in my co-pending application, Serial Number 696,841, filed November 15, 1957. The coating source includes a pair of cylindrical carbon crucibles 12 and 14, supported in vertically spaced relationship by a carbon rod 16 which threadedly engages each of the carbon crucibles 12 and 14 and by three elongated shafts 18 which are suitably secured to each of the crucibles. The lower crucible 14 is supported on legs 20 which rest on the base 10. The upper crucible 12 is heated by an in ductive heating coil 22 which surrounds the crucible 12 and a recessed melting chamber 24 in the top portion thereof for holding a molten coating material 25, such as aluminum. A suitable high frequency supply source, not shown, may be connected to the coil 22 for maintaining the coating material 25 in a molten state. A lower heating coil 26 surrounds the crucible 14 to heat the crucible and the coating material supplied to an evaporation chamber indicated generally at 27. Molten coating material is supplied to the evaporation chamber 27 fromthe melting chamber 24 through vertical-1y disposed bores 28 in the upper crucible 12. The molten coating material is vaporized in the chamber 25 by the heating coil 26 which is illustrated as comprising more turns than the coil 22 because of the large amount of heat energy that is required to evaporate the coating material as compared to the heat energy that is required to melt the coating material. The vaporized coating material is emitted in a lateral direction around the entire periphery of the source 11. The molten material in the evaporation chamber 27 is supported in a more or less vertical direction by the electromagnetic field created by the inductive coil 26. This is sometimes referred to as the pinch effect and is described in more detail in U.S. Patent No. 2,584,660 to G. H. Bancroft, issued February 5, 1952.

The coating material, which may be in the form of aluminum pellets, is supplied to the melting chamber 24 through a tube 30 which is secured to a top plate 32. The tube 30 includes a funnel 31 at the top portion thereof for receiving aluminum pellets from a coating material hopper 34. The hopper 34 is secured to a vibrating mechanism 35 for vibrating the hopper 34 to cause aluminum pellets 36 within the hopper to flow through a horizontally disposed feeding conduit 37 to the funnel 31. The vibrating mechanism 35 may be a conventional electrical vibrator and is supported by helical springs 38 which are secured to a plate 39. The plate 39 is supported by a rod 40 which is connected to an annular supporting ring 42. The ring 42 is supported by three vertically extending rods 44 which are secured to the base 10.

The top plate '10 extends over the coating source 11 and is generally conically shaped, having an axis of revolution substantially coincident with the longitudinal axis of the shaft '16 or the coating source 11. The top plate 32 includes a that portion 33 which extends under a cylindrical opening 48 in the lower end of a reservoir 50 for holding a quantity of small particles such as glass flakes to be coated. The reservoir 50 is secured to the vertical supporting rods 44 by means of braces 52. An annular opening is formed between the top plate 32 and the opening 48 in the reservoir 50 so that the thin particles Within the reservoir 50 will flow under the influence of gravity onto the top surface of the plate 32 and down the inclined surface thereof with an even distribution in all directions. A ring 54 is secured to the top plate 32 by means of brackets 56, bolts 57 and nuts 58 to serve as a secondary hopper and improve the distribution of the thin particles on the top surface of the plate 32. The brackets 56 are secured at their lower end to the top plate 32 by welding or other suitable means and include a vertically extending slot in the top portion through which the bolt 56 extends to permit the plate 54 to be adjusted up or down to control the quantity and distribution of the thin particles that slide down the plate 32 past the ring 54.

To guide the particles to be coated past the coating source 11, three frusto-conical

annular guide members

60, 62 and 64 are disposed below the top plate 32 and secured to the base by wire hinges which will be described. The

guide members

60, 62 and 64 are co-axially arranged with respect to the coating source 11 and secured together by means of three vertically extending bars 66 to maintain the guide members in fixed spaced relationship with respect to each other. The inner surfaces of the

guide members

60, 62 and 64 extend generally inwardly toward the base 10 to guide the thin particles to be coated in a downward direction past the coating source 11. The

guide members

60, 62 and 64 include vertically disposed retaining

flanges

61, 63 and 65 at the upper ends thereof to prevent the particles from spilling over the sides of the guide members during their travel past the coating source. The top plate 32 is secured to the guide member 60 by means of four spaced L-shaped brackets 67 so that the guide member 60 is disposed in an overlapping relation with the top plate 32 to cause the particles that fall from the lower edge of the top plate 32 to strike the inner surface or sides of the guide member 60. A frusto-conical annular return guide member 68 is secured to the guide member 62 by means of four L-shaped brackets 69 (only one of which is shown in FIG. 1). The sides of the return guide member 68 extend downwardly and outwardly with the upper and lower portions thereof being disposed inwardly of the bottom of the guide member 60 and the top of the guide member 62, respectively, to direct the particles that fall from the lower end of the member 60 to the upper end of the member 62. The distance between the lower edge or end of the return guide member 68 and the upper end of the guide member 60 that is disposed directly below the lower edge of the guide member 68 should be great enough to insure that the particles will fall freely between the two guide members. Another frusto-conical annular return guide member 70 which may be identical to the guide member 68 is disposed between the

guide members

62 and 64 and secured at its lower end to the guide member 64 by means of four L-shaped brackets 72 (only one of which is shown in FIG. 1). A final frusto-conical annular return guide member 74 which may also be identical to the

guide members

68 and 70 is disposed below the guide member 64 and secured to the bottom end thereof by means of four L-shaped brackets 75 (only one of which is shown in FIG. 1). This guide member 74 directs the particles into a chamber formed by an annular retaining ring 76 and the base '10 in which the particles may be collected.

To insure that thin particles such as glass flakes will be coated on both sides the

guide members

60, 62 and 64 are inclined downwardly so that the surfaces of such thin particles which are exposed to the coating source are nearly all reversed each time that the particles fall onto the members 60, 62 and '64. In this manner all of the particles are turned over at least one time and usually two times during their travel past the coating source 11. The sides of the

guide members

60, 62 and 64 may be sloped downwardly at any desired angle depending upon the time that it is desired to expose the particles to the coating source.

Cooling coils 80 may be suitably secured to the top plate 32, the

guide members

60, 62, 64 and the

return guide members

68, 70 and 74 to cool these members during the coating operation.

To impart a vibratory motion to the

guide members

60, 62 and 64 to evenly distribute the particles sliding thereon, three sets or groups of vibrating or impulsing means such as

solenoids

82, 84 and 86 are coupled between the

guide members

60, 62 and 64 respectively and rings 42, 88 and 90, as will be described. The

rings

42, 88 and 90 are supported by the vertically disposed rods 44. Each of the solenoids includes an armature, a magnetic C core and a winding designated by the letters A, C and W, respectively. The winding on each core is wound on two legs thereof, as shown, to cause the armature of the respective solenoid to be attracted to the core when the winding is energized. Each of the groups of

solenoids

82, 84 and 86 includes three solenoids which are coupled to the respective

annular guide members

60, 62 and 64 at three equidistant points on the peripheries thereof, as may best be seen in FIG. 2. Thus the solenoids that are coupled to each of the

guide members

60, 62 and 64 are symmetrically arranged and spaced 120 from one another around the circumference of the respective guide members.

The

armatures

82A, 84A and 86A are secured to the outer surfaces of the

annular guide members

60, 62 and 64, respectively, by means of

brackets

92, 93 and 94. Each of the

brackets

92, 93 and 94 include a flat plate portion designated by the letter A which is secured to the annular guide members by welding or other suitable means and four projecting tabs designated by the letter B, two of which are bent over the top of the armatures and two of which are bent under the bottom of the armatures to fasten the armatures to the brackets.

To support the top of the assembly including the

guide members

60, 62, 64, 68, 70, 74, and the top plate 80, three pairs of wire hinges 96 are secured at one end to the ring 42 and at the other end to the plates 92A. Each of the wire hinges 96 includes two

separate wires

97 and 98 which are suitably joined together at one end and fastened to the ring 42 and the plate 92A, respectively, at the other end by welding or other suitable means. As shown in FIG. 2, two wire hinges 96 are provided to support the guide member 62 adjacent each of the solenoids 82 to permit lateral movement of the guide member assembly with respect to the ring 42.

Three pairs of wire hinges 99 (only one of which is shown in FIG. 1) which may be similar to the wire hinges 96 are secured between the ring 88 and the plate 94A of the brackets 94 to support the bottom end of the guide member assembly and permit lateral movement thereof with respect to the ring 88. The

guide members

60, 62, 64, 68, 70, 74 and the top plate 32 are secured together by the supporting bar 66 so that the entire assembly vibrates in unison in response to an energizing current flow through the windings of the solenoids, as will be more clearly described. If desired, the supporting bar 66 may be omitted and additional wire hinges may be provided to support the annular guide member 62 to one of the

rings

42 or 88.

To secure the magnetic cores 82C to the ring 42, brackets 100 are provided which include plates 100A that are fastened to the wires 97 of the wire hinges 96 and tabs 10013 which clamp the magnetic cores 82C to the brackets. As is shown in FIG. 2, the plates 100A of the brackets 100 are secured at each end to one of the wires 97 so that the wire hinges 96 support the magnetic cores of the solenoids 82 as well as the top of the guide member assembly. The magnetic cores 840 are secured to the ring 88 by means of brackets 101 which may be identical to the brackets 100 and vertically extending portions of the wire hinges 99, as shown in FIG. 1. The magnetic cores 86C are secured to the ring by means of brackets 102 which may be identical to the brackets and vertically extending wires or rods 104. Copper shoes 106, which include a flat plate portion 106A that extends between the pole faces of the magnetic core and the armature of the respective solenoids are secured to the magnetic cores of each of the

solenoids

82, 84 and 86 by means of tabs 1063 to prevent the armatures from sticking to the magnetic cores due to residual magnetism effects after the solenoids are de-energized.

To provide an optimum energy transfer from the solenoids to, the guide members, the

rings

42, 88 and 90 should be sufiiciently heavy to remain substantially stationary when the solenoids are energized.

The threesets of solenoids 82, ,84- and 8 6 may conveniently be energized in a parallel delta arrangement from a three phase source 110, as shown in FIG. 3, to establish impulses on the periphery of each of the guide members 60, 62 and '64 which move around the periphery of the guide members in much the same way that a rotating magnetic field moves. The impulses occur in sequence around the periphery of each guide member. Only the windings of the

solenoids

82, 84 and 86 are shown in FIG. 3 to" illustrate one method of connecting the solenoids to a three-phase source of power. The three sets of

solenoids

82, 84 and 86 impart a rotating vibratory motion to each of the guide members 38 through "40 which causes a uniform distribution of the particles along the guide members and thereby insures that a uniform coating will be obtained on all of the particles. g

It is, of course, not necessary that each of the annular guide members be provided with three solenoids. The apparatus may be provided with only one or two sets of three solenoids suitably connected to all of the guide members so that all three of the annular guide members will be vibrated in unison. Also, only two solenoids may be used with a two-phase source of power.

The entire apparatus of the present invention may be placed in a suitable vacuum chamber as is well known in the art. I

While thin particles such as glass flakes have been specifically mentioned as one shape of particle that may be coated in theapparatus of this invention, it should be noted that particles of any desired shape such'as spherical particles may also be coated. For example, the apparatus or" this invention has been employed to coat glass beads. The vibrating annular guide members rotate such beads so that the entire surfaces thereof receive a uniform coating. This apparatus may be utilized advantageously to coat any small particulate matter which requires a coating on all sides and which can be moved over downwardly extending guide members such as the annular guide members '60, 62. and 64.

I claim:

1. In an apparatus for coating thin particles the combination comprising a source of coating material, annular guide means disposed laterally adjacent the source of coating material, said guide means being positioned for permitting sliding of the particles therealong in a downward path past the coating source, means including the annular guide means for turning the particles over at least once during their travel past the coating source to expose both sides of the particles to the coating source, and means coupled to the annular guide means at spaced points for imparting vibratory impulses to the guide means at the respective spaced points in time sequence to uniformly distribute the particles thereon whereby all of the particles will be evenly coated.

2. Apparatus for coating particles including a source of coating material adapted to emit the coating material laterally from the source, means including at least one movable annular guide member disposed laterally adjacent the source of coating material, the guide member being arranged to cause particles received on the top portion thereof to slide along its surface in a downward direction under the influence of gravity and While exposed to the coating material past the coating source, impulsing means coupled to the annular guide member at spaced points around the periphery thereof for repeatedly imparting vibratory motion to the guide member at the respective points at different times, and means for feeding the particles to be coated to the top portion of the guide member.

3. An apparatus as defined in claim 2 wherein the impulsing means includes three solenoids connected to the base and disposed adjacent the outer periphery of the annular guide member, the solenoids being symmetrically arranged around the circumference of the guide member at an angle of 120 degrees with respect to each other.

'4. An apparatus for coating particles as defined in claim 3 wherein the impulsing means further includes a sourceof three phase energizing potential and means for connecting each of the solenoids to a different phase of the three phase source to produce impulses which move around the periphery of the guide member in time sequence.

5. Apparatus for coating thin particles including a source of coating material arranged to emit the coating material laterally from the source, guide means including a plurality of annular frusto-conical guide members disposed laterally adjacent the source of coating material for guiding the particles in a downward path past the coating source, means associated with the guide means for turning the particles over at least once during their travel past the coating source to expose both sides of the particles to the coating material, means for feeding the particles to the guide means, and means coupled to the annular guide members at three spaced points along the peripheries thereof for imparting a rotating vibratory motion to the guide members to uniformly distribute the particles on the guide members, whereby all of the particles will be evenly coated with the coating material. 6. Apparatus for coating particles with a coating material including a vertically disposed coating source arranged to emit the coating material laterally from the source, first and second vertically spaced annular guide members disposed in co axial relationship with respect to the coating source, each of the first and second guide members being arranged so that the inner surfaces thereof project inwardly toward the axis of said guide members, a reservoir of particles to be coated, means for providing a continuous flow of particles from the particle source to the upper end of the first guide member so that the particles will be evenly distributed over the inner surface of the first guide member, means for imparting a rotating vibratory motion to the first guide member to agitate the particles thereon whereby the particles will slide along the inner surface of the first guide member toward the lower end thereof with one side of the particles being exposed to the coating source, means for directing the particles from the lower end of the first guide member to the upper end of the second guide mem ber and for causing the particles to turn over so that the particles disposed on the inner surface of the second guide member will have their other side exposed to the coating source and means for imparting a rotating vibratory motion to the second guide member.

7. Apparatus for coating particles with a metal by evaporation of the metal and condensation of the metal on the particles which apparatus comprises a base, a vertically disposed coating source evaporation chamber secured to the base, a generally conically shaped top plate having an axis of revolution substantially coincident with the longitudinal axis of the coating source secured to the base, the top plate being oriented so that the sides thereof project downwardly and outwardly, a source of particles to be coated disposed above the top plate, means for providing a continuous flow of particles from the particle source to the top plate so that the particles will be evenly distributed over a substantial portion of the top surface of the top plate, first, second and third annular guide members movably secured to the base in spaced vertical planes and disposed in coaxial relationship with respect to the coating source, each of the first, second and third members having a' generally frusto-conical shape with the sides thereof projecting downwardly and inwardly, each of the first, second and third members including a generally vertically disposed retaining flange at the upper end thereof, the first member being disposed under the top plate and arranged to overlap with the lower end thereof so that particles falling off of the top plate will be caught by the upper end of the first guide member, fourth and fifth frusto-conical annular members secured to the base, the fourth and fifth members being oriented so that the sides thereof extend downwardly and outwardly, the upper ends of the fourth and fifth members extending inwardly beyond the lower ends of the first and second members respectively, the lower ends of the fourth and fifth members extending below the top of the flanges of the second and third members respectively and above a portion of the sides of the second and third members respectively a predetermined distance, whereby particles falling from the lower end of the first and second guide members will be caught by the fourth and fifth members respectively and conveyed to the upper ends of the second and third guide members respectively and means for collecting the particles after they fall from the lower end of the third guide member.

8. An apparatus for coating particles as defined in claim 7 including three solenoids connected to the base and disposed adjacent the outer periphery of at least one of the first, second and third annular guide members, the solenoids being symmetrically arranged around the circumference of said one guide member at an angle of 120 degrees with respect to each other, each of the solenoids including an armature, the three armatures being symmetrically secured to said one guide member along the periphery thereof.

9. An apparatus for coating particles as defined in claim 8 including a source of three-phase energizing potential and means for connecting the solenoids to the three-phase source to produce a rotating force on the periphery of said one guide member.

10. An apparatus for coating particles as defined in claim 7 including means for imparting a rotating vibratory motion to each of the first, second and third annular guide members to uniformly distribute the particles there- 11. An apparatus for coating particles as defined in claim 10 wherein the means for imparting a rotating vibratory motion to the annular guide members includes three solenoids individually and symmetrically coupled to the periphery of each of the first, second and third annular guide members.

12. An apparatus for coating particles as defined in claim 11 including a source of three-phase energizing potential and means for connecting the solenoids to the three-phase source to produce a rotating force on the periphery of said one guide member.

13. In an apparatus for coating small particulate matter the combination comprising a source of coating material, annular guide means disposed laterally adjacent the source of coating material, said guide means being positioned for permitting sliding of the particulate matter therealong in a downward path past the coating source, and means coupled to the annular guide means at spaced points for imparting vibratory impulses to the guide means at the respective spaced points in time sequence to uniformly distribute the particles thereon.

14. In an apparatus for coating particles the combination which comprises a source of coating material, downwardly extending guide means disposed laterally adjacent the source of coating material, said guide means being positioned for permitting sliding of the particles therealong in a downward path past the coating source and means coupled to the guide means for imparting vibratory impulses thereto to uniformly distribute the particles thereon.

References Cited in the file of this patent UNITED STATES PATENTS 2,197,792 Erickson Apr. 23, 1940 FOREIGN PATENTS 665,831 Great Britain Jan. 30, 1952