US1416796A - Coating process and apparatus - Google Patents

Description

C. T. DAVIS. COATING PROCESS AND APPARATUS. APPLICATION FILED MAY 12, 1920.

1,41 6,796. Patented May 23, 1922.

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COATING PROCESS AND APPARATUS.

Application filed May 12,

T 0 all whom it may concern Be it known that I, CHARLES T. DAVIS, a citizen of the United States, and resident of New York city, in the county of Kings and State of New York, have invented certain new and useful Improvements in Coating Processes and Apparatus, of which the following is a specification.

My invention relates to a method and apparatus for applying a coating to small articles, and is especially directed to the coating of such articles with a substance applied as a liquid and capable of hardening with comparative rapidity.

\Vhile my invention is adapted to the coating of a great variety of articles, it is especially suitable for applying a coating to medical, pharmaceutical or chemical tablets, pills, capsules, etc., which, for convenience, will be referred to generally as tablets. Such tablets are now generally coated by the tumbling process, which requires comparatively expensive apparatus and is not suited for use with certain substances owing to the violent agitation to which the tablets are subjected. My invention is likewise adapted to the application of tablet coat ings such as are set forth in my Patent Number 1,335,488.

An object of my invention is to provide a new and improved process of coating tablets, and apparatus for carrying out such process, which will apply to a tablet a coating of fluid or viscid material in such a Way that the tablet will be evenly covered therewith. Another object is to provide such a process and apparatus capable of rapid and inexpensive installation and operation.

Another well-known method of applying a coating in liquid form which dries) or hardens in place includes the application of the liquid coating to the article, ordinarily by immersion of the article therein, and the subsequent location of the article on a suitable support while the coating hardens. This method, however, produces an uneven coating, both in thickness and in surface contour. This is caused first by'the engagement of the support with the article, which naturally thins or squeezes out the coating at such point; and second, by the eifect of gravity, which causes the fluid to rundown the sides and into the hollows of the article. This unevenness of contour and variation Specification of Letters Patent.

Patented May as, was.

v1920. Serial No. 330,816.

in the thickness of the coating is in many cases highly objectionable, especially when some portion of the article surface is left entirely exposed from these causes.

My invention comprises the solution of the problems connected with the application to an article of an even, uniform coating which is initially applied in liquid form and which hardens in place, and the avoidance of the objections to the tumbling and the stationary hardening processes above outlined. I have accomplished this result by initially applying a suitable amount of coating to the article, as by immersion, and then projecting the article into space, under conditions which tend to harden the coating during its flight. With this arrangement, the rough handling incident to tumbling is avoided, also the unevenness of the coating caused by the employment of a support. It also is of such a nature that only the simplest of apparatus need be employed, and a thick substantial coating may be applied evenly and in one quick operation. Furthermore, this process permits the employment of certain coating substances, as well as certain types of articles, which are. not physically capable of withstanding the shocks of tumbling, or the distorting effects of the stationary hardening system.

My improved process is adapted for use with a coating substance which may be initially applied to. tablets in fluid or viscid form and which will harden with comparative rapidity under proper conditions. These physical characteristics may be inherent in the coating material employed; but they may likewise be produced by subjectingsuch material to special treatment, either for maintaining it in liquid form during its initial application to the tablets;

for hardening the coating after such initial.

application; or for performing both operations. Various substances are well known to those skilled in the art which may be rendered fluid and then hardened by special treatment, and my invention is not restricted to the specific type of coating substance disclosed, nor to the particular method vof treating ,it for liquefying and hardening such substance, as other substances and methods of treatment can readily be substituted therefor by those skilled in the art without exercising invention,

One type of coating material suitable for the purpose is normally hard at ordinary temperatures, but is readily liquefied by heating, so that it may be readily applied to v the tablet in liquid form and hardened by cooling. The various types of Wax afford an example of this material, as they melt at comparatively low temperatures, 'and can be cooled and hardened very rapidly.'

According to my improved process the coating materialin liquid form is first applied to the tablet in any desired way, it being necessary only that the requisite amount of such material should adhere to some part of the tablet. This step may be performed in various Ways, as .by dipping or immersing the tablet in the coating substance, or by pouring, spraying or otherwise applying such substance directly to the tablet.

After the requisite amount of coating material has been taken up bysuch tablet, I

propel the latter through the air, preferably in such away that it will have a rotary or gyratory movement during flight. This step serves to distribute the coating evenly over the surface of the tablet, thls effect 'flight, and as above pointed out, may be accomplished either physically or by chemical action. Where the coating substance is liquefied by heat it may readily be hardened by exposure to cold during such flight, as by projecting it through air ofv asuitable temperature. The same result may beobtained by providing a bath of any desired fluid, such as water, at a suitable temperature, in such a position that the tablet will fall therein at the end of its flight, the

coating being immediately chilled and hardening. Where a chemical result is relied on,

it may be provided by passing the tablet during flight through a suitable gas, or y projecting it into a bath of the proper chemical.

It is to be understood that while my process is particularly suited for the applica tion of a coating entirely covering the article, it is not necessarily restricted thereto as it may be employed with equal efficiency in applying a coating to part of an article by properly regulating the amount of coat- 3 ing material. initially placed-on-the article and the relative speed with which such material is hardened.

One form of apparatus suitable for coatthereby:

tial supply of said coating material, and

means for conducting said-supply into the trough 12, such as an aperture 15 in the trough communicating with the coating fluid in the reservoir. When the coating by the application of heat, suitable means is provided for heating reservoir 14, such provided with inlet and outlet pipes 17 for maintaining a supply of heated water therein. This arrangement is particularly efas a Water jacket 16, which preferably is A "material is maintained in fluid condition fective in keeping waxy coating material I at an even temperature.

The tablets falling into trough 12 drop into the coating solution therein and are covered I provide means for removing each tablet after it has been immersed, and for projecting it through the air for a substantial distance. A convenient arrangement comprises a plurality of blades or flippers 18 mounted radially'on a rotating shaft 19 and of suflicient width to extend across substantiall the entire width of trough 12. In the pre erredform disclosed, blades 18 are made entirely of spring material; but

it is apparent that other suitable constructions having resilient tablet-engaging and projecting members may be provided. The feeding of tablets 10 .into trough 12, and the rotation of shaft 19, are preferably timed so that a tablet will be dropped into the trough in advance of each blade 18. As the end-of each-blade moves along thebottom of cent the sides of blades 18, to permit the coating material to flow past said blades, preventing it from being removed from the trough thereby. As each blade rises, it carries a tablet 10 out of the coating solution and up to the top .ofsaid trough at the end opposite to chute 11. At or adjacent this point, I preferably employ suitable means engaging the end portion of said blades to cause them to project the tablet through the air. Where resilient blades or blade parts are employed,'s11ch element may con emme construction being such that the continued movement of the blade will carry its resilient end past the abutment with a sudden snap, flipping the tablet supported by such end 1nt0 the air.

In the form disclosed, I have employed a simple trip arm 20 projecting over the edge 0f trough 12 into the path of the ends of blades 18 a sufficient distance to engage said ends, but not enough to permit a tablet to be crushed between the blade and arm 20. WVhen the parts are proportioned along the lines generally indicated in the drawings,

the tablet 10 will rest upon the upper surface of blade 18 while it is bent by engagement" with trip arm 20, and will be flipped into the air as said blade snaps past the arm upon continued rotation of shaft 19. However, my invention is not restricted to this.

specific arrangement, as obviously many variations in the method of supporting and guiding the tablet and of tripping the arm may be substituted for the one shown by those skilled in the art, without departing from my invention.

By properly proportioning the parts, the tablet when projected in this manner will have a rotating or gyratory movement,

.surface 22- to prevent damage to the coating of the tablets. In order. to catch any surplus coating material a drip pan 23 may be provided adjacent arm 20, so located that any overflow from the trough 12', and any spattering as the tablets are flipped through the air, will be caught by the pan and returned to tank 14, pan 23 preferably being adjacent to or dipping into the water jacket 16 so that the coating therein may be maintained in fluid condition. The form of tablet produced is shown in Figure 3, and consists of the tablet body 10, and an outer coating 24 evenly'spread over the entire surface of said tablet body.

It will be apparent that numerous variations in the apparatus disclosed may be made, either for accomplishing substantially the same mechanical results, or for adapting the apparatus'to the employment of coating materials other than those liquefied by heat.

It is also'to be understood that while I have disclosed 'a. form of apparatus which is exclusively adapted to the carrying out of my improved process, I am fully aware that such process may be carried out by other types of apparatus. In particular, such process is not limited to the propulsion of the tablets through the air by positive mechanical impulse counteracting the effect of gravity, nor is it limited to the direct engagement of amechanical propelling element with the tablet, as other methods of propulsion are well-known to those skilled in the art and may be applied to such process.

While with certain substances one of the results produced by the projection into space of the article carrying a liquidcoating is the even distribution of the coating over the surface while still in fluid condition, it will be apparent that the coating as applied may be substantially even; and under such condition it isnot necessary to spread-the coating evenly by means of suitable projection of the article into space. \Vhen this is the case, such projection is solely for the purpose of permitting the coating to harden evenly; and it will be understood that the omission of the distributing, step during projection is within the scope of my invention.

I have employed the term fluid in the claims in its broadest sense, as covering both liquid and gaseous substances through which the article may pass during hardening of the coating.

I claim:

1. A coating process, including the application to pills and like articles of coating material in liquid form, by immersing the articles in such material, and the subsequent forcible projection of the articles through space in unsupported flight.

2. A coating process, including the appli-.

ing fluid at a temperature below the liquefying point of said material, the article hemg unsupported during passage through said fluid for a sufficient period to permit the hardening of the coatingthrough reductlon of temperature by said fluid.

4. A coating process, including the application to anarticle of a coating material hav ing a point of liquefaction above ordinary atmospherictemperature. said material being applied to the article while in liquid form, and the subsequent forcible upward projection of the article into air at ordinary temperature, the article remaining'unsupported in the air for a period sufficient to harden by cooling the coating-material carried thereby.

5. A coating process, including the application to an article of coating material including wax liquefying at a point substantially above ordinary atmospheric temperature, the wax being heated and applied in liquid form, and the subsequent forcible upward projection of the article through air at ordinary temperature, the article being unsupported in the air for a period suflicient to permit the coating to harden.-

1 6. A coating apparatus, including means for applying a fluid coating to the surface of an article, and means for forcibly projectin the coated article through space. 7. pparatus' for coating pills and like articles, comprising a coating trough, aflexi- A ble blade arranged to move articles through ally on the shaft and arranged to move artithe trough, and blade retarding means to cause the blade to flex and forcibly discharge a coated article.

ing liquid coating to the trough, a rotary shaft, flexible impeller blades mounted radicles along the trough bottom through the coating medium, and means near the dis charge end of the trough for flexing. and releasing the blades whereby successive coated articles are forcibly impelled through air and the coating evenly distributed and hardened.

a rotary shaft, flexible impeller blades mounted radially on the shaft and arranged to move articles along the trough bottom through the coating medium, and means near the discharge end of the trough for flexing and releasing the blades whereby successive coated articles are forcibly impelled through air,.'and the coating evenly distributed and hardened.

10. Apparatus for coating pills and like articles, comprising a coating trough having an arcuate bottom, means for supplying liquid coating to the trough, means for maintaining the coating in liquid condition, a rotary shaft, flexible impeller blades mounted radially on the shaft and arranged to move articles along the trough bottom through the coating medium, means near the dlscharge end of the trough for flexing and releasing the blades whereby successive coated articles are forcibly impelled through air and the coating evenly distributed and hardened, means for supplying articles successively to the coating trough, means for catching the coated articles, and means for receiving coating material discharged by the blades and returning it for resup'ply to the trough.

Signed at New York city, in the county of Kings and State of New York, this 11th day of May, A. D. 1920.

0 CHARLES DAVIS.

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