US 2648609 A
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Description (OCR text may contain errors)
Aug. 11, 1953 D. E. WURSTER METHOD OF APPLYING COATINGS TO EDIBLE TABLETS OR THE LIKE Filed Jan. 21, 1949 RECOVER Y Alva Ex HA us 1- AIR Duscmme: ALONG WALL OF COMPRESSED OUTLET To Pou SHING PAN IN V EN TOR.
Patented Aug. 11, 1953 METHOD OF APPLYING COATINGS TO EDIBLE TABLETS OR THE LIKE Dale E. Wurster, Madison, Wis., assignor to Wisconsin Alumni Research Foundation, Madison, W1s., a corporation of Wisconsin Application January 21, 1949, Serial No. 71,997
6 Claims. 1
My invention relates, generally, to methods of and means for applying coatings, and it has particular relation to the coating of medicinal tablets, chewing gum, candy, nuts, etc.
Among the objects of my invention are: T support the tablets in air in a coating chamber and to coat the same While they are so positioned; to support the tablets in an upwardly flowing air stream; to heat the air prior to its contact with the tablets to dr the coating thereon; to cause the air to flow in a turbulent fashion and tumble the tablets so that they may be coated uniformly; to move the tablets downwardly on a bias transversely of the air stream while they are being coated; to introduce the coating material into the air stream under neath its initial contact point with the tablets; to introduce individually into the air stream different coating materials; and to direct a current of air upwardly in the coating chamber along its inner surface to prevent the coating material from impinging thereon.
Other objects of my invention will, in part, be obvious and in part appear hereinafter.
This invention is disclosed in the embodiment thereof shown in the accompanying drawing and it comprises the features of construction, combination of elements, arrangement of parts and method steps which will be set forth in detail hereinafter and the scope of the application of which will be indicated in the appended claims.
For a more complete understanding of the nature and scope of my invention, reference can be had to the following detailed description, taken together with the accompanying drawing, in which:
Figure l is a longitudinal sectional view of a coating mechanism constructed in accordance with my invention;
Figure 2 is a View partly in section and partly in elevation at an enlarged scale showing in more detail the construction of the manifold which directs air upwardly along the inner surface of the coating chamber; and
Figure 3 is a top plan View of the rotating disc which causes the air to flow in a turbulent fashion. 7
Referring now particularly to the drawing, it will be observed that the reference character I'll designates a vertically positioned coatin chamber which may be formed of metal or glass. The coating chamber Ill preferably has a circular cross section, and it may be of conical, modified conical, or cylindrical shape as may be desired. Near its lower end there is provided an entrance I I for the tablets to be coated. An inlet tube [2 communicates with the entrance and slides l3 and 14 are positioned therein to permit the introduction of the tablets to be coated into the chamber Ill in batches.
Within the chamber In there is a screen I which extends transversely thereacross and on a bias so that the tablets to be coated and while they are being coated move across the chamber Ill and downwardly to an exit ['6 with which an outlet tube ll communicates. The tube Il may discharge into a polishing pan or similar receptacle. Slides l8 and It may be provided in the outlet tube I! for. controlling the flow of the coated tablets theretln'ough in batches similar to the manner in which they are permitted to flow onto the screen l5 by the slides l3 and M.
It is desirable that the uncoated and partially coated tablets above the screen l5 be supported in air so that they can be evenly coated. For this purpose air jets 20 and 2| are positioned in the lower end of the chamber Ill below the screen l5 and are directed upwardly to suppl an air stream flowing upwardly in the chamber H) of sufiicient velocity to maintain the uncoated and partially coated tablets slightly out of contact with the screen l5. The air jets 20 and 2| may be connected by conduits 2B and 2| to a suitable. source of compressed air, the pressure of which is adjusted so as to maintain the uncoated and partially coated tablets slightly above the screen l5 to be coated in a manner to be described presently.
Not only is it desirable that the tablets be supported in the air stream which flows uD- wardly through the coating chamber I0 but also it is desirable that they be tumbled so as to coat the same more uniformly. For this purpose the flow of air through the coating chamber II] is arranged so that, in place of it being a streamlined flow, it is a turbulent flow. For this purpose a disc 22 is provided which may be rotated at a constant speed by a motor 23. As shown more clearly in Figure 3 the disc 22 has circular rows 24, 25, 26, and 21 of perforations through which the air from the jets 20 and 2| flows. As shown in Figure l the air jets 20 and 2| register with the circular rows 24, 25, 26, and 21 of perforations so that the air from the former is d rected byv the row of perforations individual thereto. Also as shown in Figure 1 the rows 24 and 21 of the perforations are inclined inwardly while the row 25 ofperforations is inclined outwardly. The remaining row 26 extends Vertically through the disc 22. The several air streams thus directed by the perforations 24, 25, 26, and 2'! impinge on the uncoated and partially coated tablets above the screen IS in a turbulent fashion and cause them to be tumbled so that they can be evenly and completely coated with the coating material.
With a view to drying quickly the coating material on the tablets, provision is made for heating the air as it passes upwardly through the chamber ll) underneath the screen [5. For this purpose an electric heater element 28, in the form of a grid, may be positioned immediately above the rotating disc 22. It will be understood that the heater element 28 maybe connected for energization to a suitable Current source and that the degree of heat can be varied by varying the amount of current fl g.
The material for coating the tablets may be supplied through conduits 30, 3| and 32, the number being determined by the number of different coating materials to be employed. Each of the conduits 30, 3| and 32 terminates in a nozzle 33 which, as shown in Figure 1, is directed against the tablets near the upper edge of the screen l5 so that the coating material is supplied to the tablets as soon as they pass through the entrance II. It will be understood that various coating materials can be supplied. As illustrated in Figure 1, the conduit is arranged to have powdered lactose blown therethrough. The conduit 3| carries an acacia solution, while the conduit 32 may carry a sugar solution. It will be understood that these particular materials are mentioned for illustrative purposes only and that other coating materials can be used as may be desired.
Certain of the coating materials may tend to adhere to the inner surface of the coating chamber Ill particularly in the immediate vicinity of the screen l5. In order to prevent this a ringlike manifold 34 may be positioned just above the screen I5. As shown in Figure 2 the manifold 34 has outwardly and upwardly directed openings or apertures 35 which cause air supplied to the manifold 34 from a suitable source of compressed air to flow in the directions indicated by the arrows 36 over the inner surface of the chamber In for preventing the coating material from engaging the same.
At the upper end of the coating chamber II] a screen 31 may be provided to prevent the escape of tablets in the event that the pressure supplied through the jets 20 and 2| should be sufficiently great as to cause them to rise to this position. An exhaust tube 38 connects the coating chamber II) to a suitable recovery and exhaust chamber as will be understood readily.
In operation, the motor 23 is energized to drive the disc 22 at the desired speed. Air under pressure is supplied through the conduits 20' and 2| to the jets 20 and 2| respectively so that the uncoated and partially coated tablets on the screen I5 will be tumbled thereabove. This air pressure also is adjusted so that when the tablets are fully coated it will be insufficient to maintain them above the screen l5 at the lower end thereof adjacent the exit [6. The current flowing through the heating element 28 is adjusted so that the coating applied to the tablets above the screen I5 is dried satisfactorily. The coating materials supplied to the conduits 30, 3| and 32 are arranged and adjusted so that the desired proportions will be applied to the tablets at rates which will provide the desired thickness of coating. Air is supplied to the manifold 34, it being understood that the pressure at the apertures 35 therein is slightly greater than the air pressure at the air jets 20 and 2| so that the desired air flow takes place along the inner surface of the chamber [0 to prevent the coating material from impinging thereon.
Now, the slide I3 is raised to permit a charge of uncoated tablets to flow downwardly through the inlet tube I2 against the slide Id. The slide I3 is closed and then the slide I4 is opened. The uncoated tablets flow through the entrance II onto the upper end of the screen I5 and are immediately lifted thereabove and tumbled. At
4 the same time they are subjected to the atomized flow of coating materials from the nozzles 33 which are supplied individually by the conduits 30, 3| and 32 in the manner described. The partially coated tablets move transversely of the chamber .IO and downwardly on a bias but are still being tumbled above the screen l5 until the coating thereon is sufficiently heavy so that the upwardly flowing air stream is insufficient to maintain them out of contact with the screen '|5. When all of the tablets have been completely coated, the slide I8 is opened and they are allowed to dischargethrough the exit l6 into the outlet tube II. Thereafter the slide 18 is closed and the slide I9 is opened to permit the coated tablets to be discharged into the polishing pan or other receptacle as may be desired.
It will be obvious that certain changes can be made in the foregoing construction and method without departing from the spirit and scope of this invention. Accordingly, it is intended that all matter shown in the accompanying drawing and described hereinbefore shall be interpreted as illustrative and not in a limiting sense.
I claim as my invention:
1. The process of covering eatable tablets of the type of medicinal tablets, chewing gum, candy and nuts with a sugary coating which comprises: moving an air stream in a confined space upwardly past the eatable tablets with a force sufiicient to suspend them continuously therein, and introducing the sugary coating material into said air stream prior to its contact with the eatable tablets.
2. The invention, as set forth in claim 1, wherein the coating is wet on application and the air stream is heated to dry quickly the coating applied to the tablets.
3. The invention, as set forth in claim 2, wherein the air stream is turbulent to tumble the tablets whereby they receive a coating of uniform thickness.
4. The invention, as set forth in claim 1, wherein the tablets move downwardly on a bias transversely of the air stream while being coated.
5. The invention, as set forth in claim 4, wherein the coating material is introduced into the air stream at a position close to the initial contact point thereof with the tablets.
6. The invention, as set forth in claim 1, wherein the coating material comprises a plurality of different materials and they are introduced separately into the air stream.
DALE- E. WURSTE'R.
References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 1,473,165 Steigmeyer Nov. 6, 1923 1,546,922 Faber July 21, 1925 1,725,608 Zebulski Aug. 20, 1929 2,059,983 Dent et al. Nov. 3, 1936 2,259,879 Denning -1 Oct. 21, 1941 2,339,932 Kuhl Jan. 25, 1944 2,349,230 Thomas May 16, 1944 2,399,717 Arveson May 7, 1946 2,447,006 Gamson Aug. 17, 1948 2,459,836 Murphee Jan. 25, 1949 2,491,632 Wieder Dec. 20, 1949 2,493,198 Kelley, Jr. Jan. 3, 1950 2,498,405 Fader Feb. 21, .1950 2,536,168 Goggin Jan. 2, 1951 2,561,392
Marshall July 24, 1951