US2912172A

US2912172A - Sterilizable centrifugal atomizer for spray driers

Info

Publication number: US2912172A
Application number: US696389A
Authority: US
Inventors: Moller Aage
Original assignee: Individual
Current assignee: Individual
Priority date: 1956-11-27
Filing date: 1957-11-14
Publication date: 1959-11-10
Anticipated expiration: 1976-11-10

Description

A. MQLLER Nov. 10, 1959 STERILIZABLE CENTRIFUGAL ATOMIZER FOR SPRAY DRIERS Filed Nov. 14, 1957 2 Sheets-Sheet l M. v I'll AAGE MQLLER INYENTOR :XuflPnM/ AH' s STERILIZABLE CENTRIFUGAL ATOMIZER FOR SPRAY DRIERS Filed Nov. 14, 1957 A. MQLLER Nov. 10, 1959 2 Sheets-Sheet 2 INYENTOR E R AAGE Mou.

Mum

ATTORNEYS L ,chamber of known type.

STERILIZABLE CENTRIFUGAL ATOMIZE FOR SPRAY DRIERS The invention relates to a sterilizable centrifugal atomizer. Such atomizers are e.g. used for the production of powders by the atomization of a liquid in a drying chamber. The invention also relates to a device comprising such atomizer fastened in the walls of a closed vessel in which the atomization and drying of the liquid take place.

The invention has for its object to provide an improved centrifugal atomizer which can be sterilized effectively before being put into operation and which can be maintained sterile during the operation:

In a device for the production of powders which'have to be sterile, e.g. medical preparations, the atomizer is generally sterilized, before being started, by means of sterilizing vapour. During the operation sterilized compressed air is supplied to the atomizer in order to prevent bacteria from entering the sterilized parts thereof. The vapour should be prevented from entering the shaft journals and the gear box of the atomizer, because there it would cause damage, and therefore it is necessary to make a sealing between the place where the vapour is supplied to the atomizer and said journals and gearbox. An ordinary packing cannot be used for this purpose because of the very rapid rotation of the atomizer shaft, and further such packing would prevent the flow of the sterilized compressed air through the journals which would be a disadvantage since this very flow prevents bacteria from entering the sterilized part of the atomizer and further prevents foreign materials, as e.g. oil drops from the journals, from reaching the sterilized atomization wheel. 7 V According to the invention the atomizer comprises valve means which can provide the necessary sealing and which can be opened and closed by the axialdisplace- .ment of the atomizer shaft.

Another object of the invention is means for axial displacement of said shaft between two positions, in one of which the valve means is closed and in the other of which, corresponding to the operational condition of the atomizer, the valve means is open.

A further object of the invention is means for preventing the starting of the atomizer when the shaft is'not :in its operational position.

Other and further objects and advantages of the invention will appear from the following description referring to the accompanying drawings showing an embodiment of the invention, V

Fig. 1 illustrates partly in section, an apparatus comprising an atomizer according to the invention,

Fig. 2 illustrates on a larger scale and partly in'section the atomizer shown in Figi Fig. 3 is a view in the direction of arrows III in Fig. 4, and

Figs. 4 and 5 are sectional views, corresponding to ,:Fig. 2 but on a larger scale, of the upper and lower parts, :respectively, of the atomizer shaft.

Fig. 1 shows a closed vessel 101 enclosing a drying v In the upper part 1 of said vessel is an atomizer according to the invention, of which States Paten a screen 2, a top part 4, and an electric motor housing 13 may be seen in Fig. 1. Further, the atomizer wheel 21 proper is shown. A tube 34 serves for supplying the liquid to be atomized and another tube 102 serves for supplying a drying medium, as e.g. hot air, to the chamber. Finally, a tube 41 is shown, the purpose of which is to supply sterilizing vapour and sterilised compressed air, and which may, through a changeover valve 103, be selectively connected to tubes 1614 and leading to devices for supplying vapour and compressed air, respectively.

As will appear from Fig. 2, the atomizer housing comprises besides the screen 2 and the top part 4, also a bottom part 5 secured to said top part 4 by means of screws 6. The top part is screwed onto the screen 2 by screws 7 and rests on the upper part or roof 1 of the drying chamber. The bottom part5 fits into a ringshaped member 3, and a seal between these two parts is provided by means of a sealing ring 8.

The top part 4 contains a gear box 9 closed by a lid 10 secured by .a ring 11 screwed onto the top part by means of screws 12. The lid 10 is integral with the housing 13 of the electric motor, the shaft 14 of which penetrates into the gear box 9 and carries a gear wheel 15 in mesh with a gear wheel 16.

At one side of the gear box 9 there is an inspectionglass 17, which is secured by means of a nut 19 and sealing rings 18 to top part 4, and through which the rotation of the gear wheels may be observed and the oil level of oil in the gear box checked.

To one end of a shaft 20, projecting from one end of the housing, the atomizer wheel 21 is secured by means of a washer 22 and the nuts 23 and 24 (see also Fig. 5) whereas the other end of the shaft 20 carriesv the gear wheell (see also Fig. 4). In the atomizer wheel 21 there is provided a circular groove 25 concentric with the shaft 20. The limiting wall of the groove 25 nearest the shaft 20 has steps 26. From the groove 25 a number of channels having rectangular cross-section and the inlets of which are designated 27, extend to the periphery of the atomizer wheel. The open channels are covered by a lid 28 secured to the atomizer wheel 21 by means of rivets 29 so as to form closed channels of rectangular cross-section.

Immediately above the atomizer wheel but without contacting said wheel, a so-called liquid distributorfis disposed, said distributor being constituted by a circular disc 30 which by means of a vertical flange 31 is screwed onto the bottom part 5. In the disc 30 there is a groove 32 concentric with the shaft 20 which com,- municates with a number of holes 33. The supply tube 34 for the liquid to be atomized opens into the groove 32 and at the other end has a pressure-tight connection at a flange on the top part comprising a stufiing box 35 and a packing gland 36. The tube 34 ends at top in a threaded connection 37.

During operation, the shaft 20 and consequently also the atomizer wheel 21 is set into rapid rotation by means of the electric motor which drives the shaft through the

gear wheels

15 and 16. The shaft 20 is journalled in ball bearings 38 and 39, the construction of which will be explained in detail below. The liquid to be atomized is supplied to the upper end of the tube 34, flows through said tube into the groove 32, from where it continues through the holes 33 down on the steps 26 in the atom-' izer wheel 21 where, as a consequence of the centrifugal force, it will be flung outwards in a radial direction towards the outer wall of the groove 25 where it flows in through the inlets 27 into the channels of rectangular cross-section. Likewise as a consequence of the centrifugal force, the liquid flows further outwardly through the channels until with great velocity it gets to the circumference of the atomizer wheel, from which the atomization of the liquid takes place. The steps 26 have for their purpose to cause an even distribution of the liquid over the cross-section of the inlets 27 of the channels, and a circular flange 40 on the disc 30 has for its purpose to prevent liquid from being flung out of the atomizer through the space between the lid 28 of the atomizer wheel and the disc 30.

As the atomizer is designed for use in a device for the production of sterile substances, the parts of the atomizer and also the other parts of the device coming into contact with the liquid to be atomized and the powder produced, must be sterilized before the atomizer is put into operation. Therefore, the atomizer comprises the supply tube 41 for sterilizing vapour, said tube extending by means of an air tight connection through the flange of the upper part 4 through a stufiing box 42 and a packing gland 43. The tube 41 which at the top is provided with a threaded connection 44 at its lower end 46 opens into a first compartment 45 defined by partitions in the housing and surrounding the shaft 20 adjacent to the projecting end thereof.

The vapour supplied through the tube 41 will flow downwards from the compartment 45, along the shaft 20 and then outwards through the space between the disc 30 and the atomizer wheel 21 filling and sterilising effectively all cut-outs and cavities in the disc 30 and the atomizer wheel 21.

However, from the compartment 45 the vapour will also tend to flow upwards along the shaft 20 and will, if no other measures are taken, penetrate into a second compartment constituted by

spaces

47 and 48, which are also defined by partitions in the housing and in which the bearing 39 for the shaft are located, and possibly further upwards through the bearing 38 and the gear box 9. As the vapour has a detrimental effect on the ball bearings and the gear wheels, the latter flow of vapour must be prevented. The use of a conventional packing for this purpose situated in the passage between the

compartments

45 and 47 has proved to be ineffective in an atomizer of the type herein described on account of the very high speed of rotation of the shaft 20. Consequently, provision has been made in said passage of a valve means so constructed that when the shaft 20 is axially displaced from its position of operation, viz. the position shown in Fig. 2, the valve means provides a vapor-tight seal between the compartment 45 on one hand and the

compartments

47, 48 and 9 on the other hand. This valve means comprises a first member consisting of a steel ring 49 which is shrunk onto and forms a vapour-tight seal with the shaft 20 and a second member consisting of a plastic bushing 50 which is pressed into and forms a vapour-tight seal with a cylindrical part 51 of the bottom part 5, which cylindrical part surrounds the shaft 20, said bushing being provided with a hole in which the shaft 20 can freely move. The ring 49 has a contact surface 52 at right angles to and surrounding the shaft 20, and the bushing 50 has a corresponding contact surface 53. The distance between the two surfaces 52 and 53 is so chosen that by the axial displacement of the shaft 20 from its position of operation, they can be brought into engagement with one another whereby a vapourtight seal between the

spaces

45 and 47 is provided. For the purpose of further securing a vapour-tight seal, the surface 53 is provided with a number of ribs 54 concentric with the shaft 20.

For the purpose of obtaining the axial displacement, the shaft 20 is journalled in the following manner. The ball bearing 39 is secured to the shaft 20 between the ring 49 and a shoulder 55 and is displaceable in an axial direction in a ring 56 which is prevented from being axially displaced by a shoulder 57 on the bottom part and a locking ring 58 in the top part 4 and from being turned by a pin 59. To prevent the lubricant used for lubricating the ball bearing 39 from pcntraiing down into the compartment 45, the ring 49 and the bushing 50 are designed as a conventional labyrinth seal which causes the lubricant to be collected at the bottom of the compartment 47 from which it is pumped up by means of a hand pump 69, the suction opening 61 of which is shown in Fig; 2. The ball bearing 38 (see also Fig. 4) is secured on the shaft 20 between a steel bushing 62 which is shrunk onto the shaft 20, and a cylindrical bushing 63 which is secured against axial displacement by a clamping device consisting of

parts

64 and 65. The ball bearing 38 is displaceable in an axial direction in a cylindrical bushing 66 secured to the top part 4 by means of screws 67 and in the operative position of the atomizer is pressed against an inwardly projecting flange 68 on the bushing 66 by a number of disc springs 69 which rest against a locking ring 70. The bushing 62 and the flange 68 are designed as a labyrinth seal to prevent the lubricant for the

gear wheels

15 and 16 from penetrating into the ball bearing 38.

When the shaft is not influenced by external axial forces, under the effect of the springs 69 operating through the ball bearing 38, it will be kept at an upper position, i.e. at the operative position, in which the surface 52 and the surface 53 with the ribs 54 do not contact each other, and in which the shaft 20 can, therefore, rotate freely in the bearings 38 and 39.

The axial displacement of the shaft 20 required for closing the valve means in the embodiment shown is provided by an adjusting means comprising a rod 71 which is shown in detail in Fig. 3, and which has a cylindrical portion 72 of small diameter, and an adjacent conical portion 73. By means of a cylindrical portion 74, the rod 71 is mounted in the wall 4 of the gear box in a bushing 75. A thread 76 is in engagement with a threaded bushing 77 in the wall 4 of the gear box. One end of the rod 71 is provided with a hand-wheel 78.

In the operative position of the atomizer, the rod is screwed as far to the right, Fig. 3, as possible. In this position, the cylindrical portion 72 is located above the uppermost end of the shaft 20 which, however, it does not touch, see Figs. 2, 3 and 4, in that the upwards movement of the shaft 20 is limited by the abutment of the ball bearing 38 against the flange 68. If the rod is rotated so as to move to the left, Fig. 3, the cylindrical portion 74 is displaced in the bushing 75, and the conical portion 73 moves over the end of the shaft 20 which is thereby displaced downwards against the force of the springs 69 until the ribs 54 abut the surface 52 thereby securing a vapour-tight sealing between the

compartments

47, 48 and 45.

Since the valve means would be damaged if the atomizer was started with the valve means in the closed position, provision has been made for means for preventing such starting, said means comprising a pin 79 resting against the stationary portion of the ball bearing 38 and extending through holes in the flange 68 and the lid 10 to the top surface of said lid, where the pin 79 operates an electric switch 80 which is closed only when the ball bearing 38 and consequently the shaft 20 are in their top positions, and the two parts 49 and 50 of the valve means are, therefore, not in engagement with one another. The

switch 80 is connected in the electric circuit of the motor and prevents the motor from being started when the shaft 20 is not in its operative position.

When starting the device, the following operations should be made.

At first, the rod 71 is turned so as to move to the left, Fig. 3, whereby the valve means is closed in the manner stated above. Next, the change-over valve 103 is so positioned that vapour is supplied from the tube 104 through the tube 41 from which it flows through the tube end 46 into the compartment 45 and from there downwards along the shaft 20 and out through the space between the atomizer wheel 21 and the disc 30 of the liquid distributor. 0n the other hand the vapour canr S V not flow upwards into

compartments

47, 48 and 9 and cannot, therefore, damage ball bearings and gear wheels. When the atomizer has been sterilised the position of change-over valve 103 is changed so that sterilised compressed air is now supplied from the tube 105 instead of vapour. Then, the shaft 71 is turned so as to move to the right, Fig. 3, whereby the shaft 20 is brought into its operative position. The atomizer can now be started and the liquid to be atomized supplied through the tube 34.

Besides flowing downwards along the shaft 20, the sterilised compressed air supplied as long as the atomizer is in operation flows also upwards along said shaft, through the valve means and the ball bearings into the gear box where it escapes through casual leaks. This flow of sterilised compressed air has for its purpose to prevent bacteria from making their way from the nonsterilised part of the atomizer into the sterilised part, and further to prevent impurities, for example, oil drops from the ball bearing 39, from penetrating to the atomizer wheel. For the purpose of increasing the resistance of flow of the downwardly-directed flow of compressed air and, consequently, insuring that a suitable part of the supplied compressed air flows upwards, the disc 30 of the liquid distributor is provided with a number of circular grooves 81.

The invention is not limited to the embodiment shown on the drawing. Thus, the two members 49 and 50 of the valve means need not to be made of the above materials. They can both be of the same material, for example plastic or steel, in which latter case some kind of packing is expediently placed between the members. The two members 49 and 50 need not be separate parts secured to the shaft 20 and the bottom part 5, respectively, but may be integral with and, consequently, of the same material as 20 and 5, respectively. If the members 49 and 50 are made of materials which in themselves provide a sealing effect when the surfaces 52 and 53 are pressed together, the ribs 54 may be omitted.

The supply tube 41 for vapour and compressed air may consist of two separate tubes, whereby the change-over valve 103 may be omitted.

For the axial displacement of the shaft 20, other means than those shown on the drawing can be used. The main thing is that the shaft 20 has a definite position of operation where it is prevented from being axially displaced, and that when not in operation it can be displaced enough so that the valve means closes the passage between the first compartment and the other compartment(s). If a spring load is used, the direction of the spring force may be opposite the direction used in the embodiment, in which case the sealing is effected by means of the spring pressure while the shaft must be kept in the operative position by means of a special device acting through one or both of the bearings.

The adjusting means need not be a rod having a conical portion and extending at right angles to the atomizer shaft. For example, it can be constituted by a rod or pin being parallel with, and adjustable in, the direction of the shaft, said rod or pin acting either directly on the shaft or through one of the bearings of said shaft.

What I claim is:

l. Sterilizable centrifugal atomizer comprising a housing, bearings mounted in said housing, a shaft rotatably journalled in said bearings, one end of said shaft projecting from one end of said housing, an atomizationwheel fastened to said projecting end of said shaft, means for rapid rotation of said shaft, means for the supply of the material to be atomized to said wheel, a first partition in said housing defining with said housing a first compartment surrounding said shaft adjacent to said projecting end thereof, a second partition in said housing spaced from said first partition and defining therewith and with said housing a second compartment also surrounding Said shaft, one of said bearings being in said second 6 partition, said first partition being spaced from said shaft to leave a passage therethrough interconnecting said first and said second compartments and surrounding said shaft, means bearing on said shaft for axial'displacement of said shaft, valve means situated in said passage and operable by said shaft when it is axially displaced, and supply means connected to said first compartment for separate supply of sterilizing vapour and of sterilized compressed air to said first compartment.

' 2. Sterilizable centrifugal atomizer as claimed in claim 1, wherein said means for the supply of sterilizing vapour and sterilized compressed air comprises a single tube opening at one end into said first compartment and having at the other end selection means for separate supply of sterilizing vapour and sterilized compressed air.

3. Sterilizable centrifugal atomizer comprising a housing, bearings mounted in said housing, a shaft rotatably journalled in said bearings, one end of said shaft projecting from one end of said housing, an atomization wheel fastened to said projecting end of said shaft, means for rapid rotation of said shaft, means for the supply of the material to be atomized to said wheel, a first partition in said housing defining with said housing a first compartment surrounding said shaft adjacent to said projecting end thereof, a second partition in said housing spaced from said first partition and defining therewith and with said housing a second compartment also surrounding said shaft, one of said bearings being in said second partition, said first partition being spaced from said shaft to leave a passage therethrough interconnecting said first and said second compartments and surrounding said shaft, valve means situated in said passage and comprising a first member tightly surrounding and secured to said shaft and a second member secured tightly to said housing and having an aperture therein, said shaft extending freely through said aperture, each of said first and said second members having a contact surface surrounding said shaft, said surfaces on said first and said second members facing each other, means acting on said shaft for the maintenance of said shaft in a first position with said contact surfaces pressed against each other, resilient means bearing on said shaft for axial displacement of said shaft from said first position to a second position with a space between said surfaces and for the maintenance of said shaft in said second position, and supply means connected to said first compartment for separate supply of sterilizing vapour and of sterilized compressed air to said firstcompartment.

4. Sterilizable centrifugal atomizer as claimed in claim 3, wherein said contact surfaces on said first and said second members are substantially plane and at right angles to said shaft.

5. Sterilizable centrifugal atomizer as claimed in claim 3, wherein that portion of one of said first and second members having said surface consists of a resilient material.

6. Sterilizable centrifugal atomizer as claimed in claim 3, wherein a number of endless ribs are present on one of said surfaces, said ribs being concentric with said shaft.

7. Sterilizable centrifugal atomizer comprising a housing, bearings mounted in said housing, a shaft rotatably journalled in said bearings, one end of said shaft projecting from one end ofsaid housing, an atomization wheel fastened to said projecting end of said shaft, means for rapid rotation of said shaft, means for the supply of the material to be atomized to said wheel, a first partition in said housing defining with said housing a first compartment surrounding said shaft adjacent to said projecting end thereof, a second partition in said housing spaced from said first partition and defining therewith and with said housing a second compartment also surrounding said shaft, one of said bearings being in said second partition, said first partition being spaced from said shaft to leave a passage therethrough interconnecting said first and said second compartments and surrounding said shaft, adjusting means bearing on said shaft for axial displace ment of saidshaft, said adjusting means being situated adjacent to the other end of said shaft and being adjustable in the axial direction of said shaft, spring means acting on said shaft for the maintenance of said shaft in engagement with said adjusting means, valve means situated in said passage and operable by said shaft when it is axially displaced, and supply means connected to said first compartment for separate supply of sterilizing vapour and of sterilized compressed air to said first compartment.

8. Sterilizable centrifugal atomizer as claimed in claim 7, wherein said adjusting means comprises an adjusting rod at right angles to said shaft and having a conical part thereon situated adjacent to said other end of said shaft, and means for axial displacement of said adjusting rod.

9. Sterilizable centrifugal atomizer comprising a housing, bearings mounted in said housing, a shaft rotatably journalled in said bearings, one end of said shaft projecting from one end of said housing, an atomization wheel fastened to said projecting end of said shaft, an electric motor for rapid rotation of said shaft, means for the supply of the material to be atomized to said wheel, a first partition in said housing defining with said housing a first compartment surrounding said shaft adjacent to said projecting end thereof, a second partition in said housing spaced from said first partition and defining therewith and with said housing a second compartment also surrounding said shaft, one of said bearings being in said second partition, said first partition being spaced from said shaft to leave a passage therethrough interconnecting said first and said second compartments and surrounding said shaft, means bearing on said shaft for axial displacement of said shaft between a first and a second position, valve means situated in said passage and operable by said shaft when it is axially displaced to a closed condition in said first position of said shaft and to an open condition in said second position of said shaft, an electric switch connected in the electric circuit of said electric motor, mechanical means contacting said switch for the movement of said switch to the on-position only when said shaft is in said second position, said mechanical means contacting and being moved by said shaft, and supply means connected to said of said shaft, means for the supply of the material to be atomized to said wheel, a first partition in said housing defining with said housing a first compartment surrounding said shaft adjacent to said projecting end thereof, a second partition in said housing spaced from said first partition and defining therewith and with said housing a second compartment also surrounding said shaft and, one of said bearings being in said second partition, said first partition being spaced from said shaft to leave a passage therethrough interconnecting said first and said second compartments and surrounding said shaft, means bearing on said shaft for axial displacement of said shaft, valve means situated in said passage and operable by said shaft when it is axially displaced, and supply means connected to said first compartment for separate supply of sterilizing vapour and of sterilized compressed air to said first compartment. I

11. Device as claimed in claim 9, wherein said means for the supply of sterilizing vapour and sterilized compressed air comprises a single tube opening at one end into said first compartment, a change-over valve on the other end of said tube, a second tube connecting said change-over valve to a device for the supply of sterilizing vapour, and a third tube connecting said change-over valve to a device for the supply of sterilized compressed air.

References Cited in the file of this patent UNITED STATES PATENTS 2,584,973 Andermatt Feb. 12, 1952 FOREIGN PATENTS 481,786 Canada Mar. 18, 1952 760,660 Great Britain Nov. 7, 1956