US1985843A - Coating apparatus - Google Patents

Description

Dec. 25, 1934. B, c, SKINNER COATING APPARATUS Filed Oct. 13. 1932 ATTORNEYS Patented Dec. 25, 1934 UNITED STATES I COATING APP ARATUS Bronson Cushing Skinne r, Dunedin, Fla.,'assignor to Brogdex Company, Winter Haven, Fla., a

corporation of Florida Application October 13,

7 Claims.

This invention relates to coating apparatus; and it relates more particularly to apparatus whereby globular objects, such as fresh fruit, may be provided with an extremely thin film-like protectivecoating, and may also be given a lustrous glossy surface.

r In protectively coating certain articles, as in protectively coating fresh fruit in preparation for market for example, the necessity arises for providing a special protective coating of such nature that it is firmly adherent and relatively permanent in character but does not too completely seal the surface of the article; while at the same time the finished coating must present exteriorly a pleasing luster or shine demanded by the trade. The achievement of both these objectives in a single coating step has been found to be impractical if not impossible. But by applying the coating in two successive steps, in the first of which there is applied a suitably thin layer of a relatively soft coating material which will adhere tenaciously to the surface of the article, and in the second of which aharder coating material, capable of imparting a satisfactory luster, is superimposed upon the layer of softer material in such manner as to minimize disturbance of such underlying layer, the problem may be satisfactorily solved. 'The present invention provides apparatus suitable for carrying out such a procedure,

The apparatus of the invention is of such character that the articles to be treated may be provided initially with a'film coating of relatively soft, low-melting protective material, applied most desirably bu t not necessarily with the aid of heat and rubbing, afterwhich the, initially coated articles may then be exposed to contact with an air-suspension of minute solid particles of a different coating material adapted to complete the 40 protective coating and give the articles the desired final surface finish.

One desirable practical embodiment of the principles of the invention, as applied more particularly to apparatus for coating fresh fruit in preparation for market, is illustrated in the accompanying drawing wherein Fig. 1 is a plan and Fig. 2 a side elevation, parts being broken away and in section to show details of construction.

Referring to the drawing, 11 indicates generally an applicator unit for applying the initial filmlayer of coating material to the articles to be coated, such as oranges, grapefruit, apples or the like, for example. The articles may be continuously fed to the unit over delivery or chute board '10 by conveyor means 10. In this instance the 1932, Serial No. 637,652

applicator unit comprises a plurality of cylindrical brush rolls 12 rotatably mounted side by side in parallel, the members of each pair of adjacent brush rolls cooperating to provide an elongated runway extending lengthwise of the unit. These brush rolls may be rotated continuously by any suitable driving means. The brush rolls are enclosed in a housing 13 providing a chamber in the lower part of which, below the brush rolls,- are suitable heating means 14, such as steam coils, by which the temperature within the chamber may be maintained substantially above the melting point of the coating material to be applied in this unit, The housing 13 is provided with entrance and exit openings each guarded by 15 a flexible flap closure 13. At 15 is indicated generally a device for atomizing or nebulizing molten coating material, arranged to discharge into the interior of the housing through pipe 16 and atomizing nozzles 17, which latter are adja- 20 cent the upper or intake ends of the polisher brush rolls. These brush rolls may slope gently toward the opposite or discharge end of the polisher or brush roll unit, as indicated. The atomizing unit 15 may be of any suitable type, one particularly suitable type being that disclosed in this applicants prior Patent No. 1,830,297 of November 3, 1931 which, however, is referred to here merely by way of a desirable typical example. While means for atomizing the initially applied coating material on the fruit is most desirable, other types of applying means, not effecting atomization and not necessarilyincluding heating means, may be employed within the broader aspects of the invention. But the specific form of apparatus here illustrated affords particularly great advantages. As described in applicant's prior patent aforesaid, the atomizing unit comprises a container in which solid coating material charged thereinto is melted down and main- 40 tained molten by suitable heating means; said container, together with compressed air supply means, being so connected to the atomizing nozzles that a regulable quantity of the molten coating material may be discharged therethrough un- 5 der pressure to form a fog or mist of said material.

At 18 is a roller belt conveyor arranged to receive the preliminarily coated articles which leave unit 11 over chute board 11 and to carry them into and through a chamber enclosed by a hood or housing 19 mounted justabove the conveyor and extending across its entire width. This hood has entrance and exit openings, each covered by a flexible closure flap 19*. Another atomizing or nebulizing unit 20, similar to unit 15 above described, is arranged to atomize molten coating material through suitable nozzle means 21'into the upper part of the chamber enclosed by hood 19 but, unlike chamber v13, chamber 19 is unheatedin order that molten coating material atomized thereinto may immediately solidify in the form of very fine solid particles. A continuation or extension of head 19 is arranged below the conveyor 18, as indicated at 22, and is provided with an outlet 23 connected to the intake of the suction fan or blower 24, which is arranged to discharge into a suitable dust separator device 25, such as a cloth bag.

.At 26 is a second rotary brush roll unit or polisher to which conveyor 18 delivers articles over chute board 18 after they have passed through the chamber enclosed by the hood 19. This second polisher unit need not be enclosed by a housing and is not provided with heating means. Its brush rolls 27 are mounted and arranged to be driven continuously in the same manner as the brush rolls of the unit 11 already described.

In' operation, the articles to be coated, oranges for example, may be delivered, as by roller belt conveyor 10, to the upper ends of the runways formed by brush rolls 12 of the first brush roll unit 11. Coating material, such as paraffin wax for example, suitable'for initial application to the articles, is melted in unit 15 and atomized or nebulized through spray nozzles 17 into the chamber enclosed by the housing 13, which chamber may be heated by the steam coils 14 to a temperature sufiiciently above the melting point of the parafiin wax. The articles delivered to the unit 11 receive a small quantity of molten coating material which is sprayed upon them through spray nozzles 17, and then continue to travel down the long runways between the polisher brushes in the heated atmosphere, meanwhile being continuously subjected to vigorous rubbing by the rapidly rotating brush rolls of horsehair or the like. This ensures thorough and uniform spreading of the molten or semi-molten coating material over the entire surface of the articles in avery thin film.

The articles provided with their initial protective coating and discharged from unit 11 are received by roller conveyor 18 and are thereupon exposed to ordinary atmospheric temperature, with the result that the paraflin coating almost instantly sets or becomes solid, although it-does not at once attain its final hardness but remains noticeably tacky or sticky for a short time. In this condition the articles are carried by the conveyor 18 into and through chamber 19 where they encounter a cloud or air-suspension of minute solid dust-like particles of a coating material which is generally harder and higher melting than the coating material employed in the first coating unit 11. Ihis harder and higher melting coating material may be carnauba wax, in a typical instance, melted in unit 20v and atomized or nebulized thereby through nozzle means 21 into the chamber 19. vThe atmosphere in chamber 19 being at a temperature much below the melting point of the atomized coating material, the latter. immediately congeals or solidifies from its molten condition. The resultant cloud or air-suspension of minute hard wax particles in solid form bathes the articles as they travel through the chamber and are slowly turned over and over by the action of the ing into the separator 25 a mixtureof air and excess of suspended wax particles which latter collect in the separator and may be again used, if desired. The fan or blower thus acts to direct a systematic travel of the air-suspension downwardly through the chamber in contact with the articles, and also ensures introduction of a con-, trollable amount of cooling air from outside whereby to prevent undue rise of temperature in the chamber due to the continuous introduction of nebulized hot molten wax thereinto. This provides'a convenient way of keeping the temperature in the chamber well below the melting point of the nebulized coating material and at the same time of preventing dissipation of excess of impalpably fine wax dust particles into the surrounding atmosphere to the annoyance of the operators of the apparatus. I

Upon leaving the chamber 19, the articles with their adherent deposit of solid dust-like particles of the harder coating material pass down the runways of the brush roll polisher 26 which acts to thoroughly rub and distribute said deposited coating material uniformly over the surface of the articles, this operation being conducted at ordinary atmospheric temperature. The brush rolls 2'7 of this polisher unit may advantageously be driven at a higher rate of speed than those of polisher unit 11 in order to exert an actual bufling efiect upon the surface of the articles and develop a good luster or shine thereon. For instance, with a diameter of 7 inches, the brush rolls 27 may advantageously be driven at approximately 400 R.,P. M. to give a brush surface speed of about 800 feet per minute. Under the conditions described, the action of the rapidly rotating cylindrical brushes upon the dust-like deposit of the harder coating material, besides develop ing a fine luster, works the deposit into firm adherence with the underlying thin layer of softer coating material, which remains practically undisturbed and to which the finishing layer of harder material adheres far more tenaciously than it would adhere directly to the surface of the article.

As here illustrated, the roller conveyor 18 interposed between the two brush roll units 11 and 26 is of such length that, in the usual operation of the apparatus, the articles being coated are exposed to atmospheric temperature for a short period of time, on the order of 15 to 20 seconds,

for example, before entering chamber 19. This brush roll unit 26 to receive the initially coated articles directly from unit 11, in which case the 1,985,848 chamber 19, 22, may be'arranged at the head or articles and to coat them initially with suitably adherent coating material while directing them to a point of discharge, in combination with further applicator means arranged to receive continuously initially coated articles discharged from the first applicator means and'to provide them with a coating of luster-imparting material while directing the articles to a point of discharge, such further applicator means including an unheated chamber, a container for coating material, means for heating said container to melt solid coating material charged thereinto, and compressed air supply means, together with atomizing nozzle means connected to said container and compressed air supply means and arranged to discharge into said unheated chamber, thereby to produce a cloud or air-suspension of fine solid particles of said coating material in the path of travel of said articles, and rubbing means arranged to act on the articles upon which such solid particles are deposited.

2. Coating apparatus comprising a rotary brush roll unit, a housing enclosing the same, means for feeding articles to said brush roll unit, a device adapted and arranged to melt solid coating material and to atomize the molten coating material into contact with articles fed to such brush roll unit, and heating means adapted and arranged to maintain the temperature within said housing above the melting point of parafiin wax, in combination with a second rotary brush roll unit, means for transferring articles thereto from the first brush roll unit, and a device adapted and arranged to melt solid coating material and to atomize the molten coating material into the path of travel of such articles between the point where they leave the first brush roll unit and the point where they leave the second, such path being exposedto atmospheric cooling sufflcient to ensure solidification of such atomized molten coating material before it gmtacts said articles. 3. Coating apparatuscomprising means for applying hot molten butnormally solid waxy ma-- terial to articles to be coated, rotary brush roll mechanism cooperating therewith to rub said material over thejsurface of the articles, a housing enclosing said mechanism, and means for heating the interior of said housing, to a temperature sufiicientto prevent solidification of said waxy material while it is, being rubbed on said article, in combination with means adapted and arranged to produce from molten waxy material an air suspension of fine solid waxy particles, in an unheated environment, a second rotary brush roll mechanism cooperating therewith, and located in said unheated environment, and means for transferring articles from the first mentioned" brush roll mechanism into contact with such suspension of solid wax particles and into position to be acted upon by said second rotary brush roll mechanis 4. Coating apparatus comprising two rotary brush roll units arranged in series, a roller belt. conveyor interposed between them and arranged to receive, articles discharged from the first and deliver-them to the second, coating material supply means and heating means cooperating with the first rotary brush roll unit for applying coating material in substantially-molten condition 'to articles, and means for contacting a cloud or air-suspension of fine solid particles of coating material with articles while they are on said conveyor, said conveyor being disposed in an environment cool enough to prevent melting of said solid particles.

5. Coating apparatus as defined in claim 4, wherein a molten coating material atomizer is provided to produce the said air-suspension, and an exhausting device directs the same into the path'of travel of the articles on said conveyor.

6. Coating apparatus comprising two rubbing units arranged'to act successively on articles to be coated, means for driving said units continuously to effect travel of articles through them in a definite path, separate coating material supply devices cooperating with the respective rubbing units in the application of coating ma--' article travel into which said atomizing means discharges.

7. Coating apparatus comprising applicator means operable to coat globular articles initially with suitably adherent coating material solid at ordinary atmospheric temperatures, in combination with further applicator means operable to provide the initially coated articles with a further coating Minster-imparting material, such further applicator means including anatomi'zing or nebulizing device operable to provide a supply of such luster-imparting material in hot molten condition and to produce therefrom a cloud or air-suspension of fine solid particles of said coating material in an unheated path of travel of said articles, a housing forming a chamber within whichthe cloud or suspension of solid particles is confined, and rubbing means arranged in said unheated path to act on the articles upon which

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