GB2093719A - Filter assembly for centrifuge - Google Patents

Abstract

A filtering assembly for a centrifuge drum 1 comprises a filter screen (6) fixed to a lid (7) at the top and to a base (8) at the bottom. The top of the lid has a rib (17) provided with holes (18) in each of which a bolt (21) is inserted, and the edge of the centrifuge drum (1) has a supporting surface (2), on which the lid (7) rests, and a cylindrical wall (3) provided with holes (4) into which bolts (21) are inserted to lock the filtering assembly to the drum in a readily removable manner. When the construction is applied to a centrifuge with unloading from the base, the centrifuge housing has an operable top cover (Fig. 5 not shown) to allow the removal of the filter assembly via the top, in order to clean and/or replace it. The filter screen (6) is fixed to the lid and to the base of the filter assembly by means of respective split rings which are tensioned (via tension means 13 to 15) so as to clamp the screen against flanges (9) and (9') which are integral with the lid and with base, respectively. <IMAGE>

Description

SPECIFIC;TION Filter assembly for centrifuges The present invention relates to a centrifuge, and more particularly to an arrangement for fixing the filtering partition to the basket in such a machine.

It is know that in a centrifuge with unloading from the base the replacement of the filtering partition is a laborious operation and the mounting and dismounting of such a partition inside the basket of the machine is carried out only with considerable difficulty, due to the small volume there is in which to work, and the machine is often badly cleaned or is impregnated with dangerous substances.

Moreover, this method of operating involving a long stoppage time for the machine considerably reduces its performance, and makes it virtually impossible and uneconomical to use if the question of frequent replacement of the relevant filter should arise.

In a centrifuge with unloading from the top the problem of mounting and dismounting the filtering partition inside the basket does not arise, since the filtering partition may be removed via the top of the centrifuge, but the problem still remains of fixing the filtering partition to the basket, which has not hitherto been resolved in a satisfactory manner.

The present invention proposes to provide a fixing arrangement for fixing the filtering partition to the basket in a centrifuge which will be simpler than the known fixing arrangements and which is suitable for use either in centrifuges with unloading from the base or for those with unloading from the top.

More particularly, the arrangement according to the invention for fixing the filtering partition to the basket is characterised in that it comprises an upper annular lid to the underneath of which the filtering screen is fixed and from the top of which there projects a circular rib which is coaxial with the lid and is provided with a plurality of radial holes, with a plurality of bolts passing through the holes in a radial direction and having an abutment for engaging the lateral internal surface of the rib, and an upper edge of the basket having an annular surface for the lid of the filtering partition to rest on, and a cylindrical edge projecting upwards from the annular supporting surface and provided with a plurality of radial holes which are equal in number to the radial holes in the circular rib on the lid and which are adapted to be brought in register with the latter holes so as to be engaged with the bolts.

It will be clearly seen that with an arrangement of the type described above the filtering partition may be fixed to the basket easily by simply passing the bolts through in one direction, and may be detached from the basket equally easily by passing the said bolts through in the opposite direction.

Once the filtering partition has been released from the basket, in a centrifuge with unloading from the top the filtering partition may be removed in the same way as the filter sack in a known centrifuge.

However, in centrifuges with unloading from the base such as are being designed at the present time, this method of removal is not possible, since these centrifuges are closed at the top by a permanently attached cover. To allow the filtering partition to be taken out via the top in these centrifuges as well, according to one characteristic of the invention the cover of the centrifuge is made so that it can be opened, like a centrifuge with unloading via the top.

In this way the possibility is created in this type of centrifuge as well of mounting and dismounting the filtering partition in the area outside the machine and therefore with the additional necessity of entering and operating inside the basket, thus also affording the possibility of cleaning the inside properly when the filter has been dismounted. A centrifuge with unloading of the solid dehydrated substance via the base is therefore provided which is specially adapted for processeing products which are dangerous by reason of their toxicity or because they are allergens or the like, which, with frequent changes of the type of product being processed, also necessitates cleaning the inside of the machine thoroughly at every change.

According to another characteristic of the invention, the filter screen is fixed to the lid of the filtering partition by means of a split ring which can be set under tension so as to press one edge of the screen against one cheek of an angular profile projecting from the lower surface of the lid, coaxially therewith, thus locking the edge of the screen in place.

Such a method of fixing allows rapid replacement of the filter screen whenever this is necessary.

These and other characteristics of the invention will become clearer from the following detailed description of two embodiments therof, given purely by way of example and not therefore limitative, with reference'to the attached drawings, in which: Figure 1 is a partial axial section showing some parts of a centrifuge with unloading from the base and provided with an arrangement according to the invention for fixing the filtering partition on the basket; Figure 2 shows a detail from Fig. 1, on a larger scale; Figure 3 is a partial transverse section of a detail from Fig. 2, along the line 3-3 in Fig.

2; Figure 4 is a modified version of the detail shown in Fig. 2; and Figure 5 is a schematic illustration of a centrifuge like that in Fig. 1 with the cover open and the filtering partition lifted up out of the machine.

Referring first to Figs. 1 to 3, it can be seen that at the top the basket 1 has a widened rim with an annular supporting surface 2 and a cylindrical wall 3 projecting from the surface 2 and equipped with a plurality of holes 4, evenly distributed along the said wall.

The filtering partition, designated 5 as a whole, comprises a screen 6 fixed at its upper edge to a lid 7 and at its lower edge to a rigid base 8 attached to the spokes of the supporting cone of the machine, at a location 31.

The fixing of the screen 6 to the lid 7 is accomplished in the same way as the fixing of the said screen to the base 8, so that for the sake of simplicity only one of the two fixings will be described, and more specifically that of the screen 6 to the lid 7. To this end the lid 7 bears underneath an angular profile 9 which is welded to it, extending all the way round the edge of the lid, concentric with the said edge. For fixing the screen to the lid the upper edge of the screen is introduced in a groove formed by the lid and the angular profile and then a metal split ring 10 is introduce into the said groove, having one end 11 (see Fig. 3) welded to a small curved plate 12 with a radius of curvature substantially equal to that of the vertical flange of the angular profile 9.The other end 1 3 of the ring 10 is threaded and is inserted in a sleeve 14 welded to the curved plate 1 2 from which a length of it projects, on which a nut 1 5 and a lock-nut 16 are screwed, pressing against one end face of the sleeve 14. It will be obvious that for locking the end of the screen 6 against the vertical flange of the profile 9 it is sufficient to tension the ring 10 by screwing the nut and the lock nut 15, 16 on the threaded length 1 3 of the ring 10. It will be seen that the fixing of the creen to the lid may thus be accomplished in an extremely rapid and simple manner.For removing the screen from the lid all that is required is to proceed in the reverse manner, unscrewing the nut and the lock nut 15, 16, so as to unlock the screen so that it may be taken out of the groove formed between the lid 5 and the profile 9, having first taken the split ring 10 out of the said groove.

As already stated, the same operations as are necessary to fix the upper edge of the screen 6 to the lid 7 or to release it are also carried out to fix the lower edge of the screen 6 to the base or to release it. The parts which are involved in this operation at the base are indicated with the same reference numerals as the parts at the top, with the addition of an apostrophe.

Projecting from the top surface of the lid 7 there is a circular rib 1 7 in which a plurality of holes 18 is formed, distributed evenly around the rib with identical angular spacing to that of the holes 4 in the wall 3 on the basket 1. Corresponding with each hole 18 there is a small bridge 1 9 which is integral with rib 17 and has an aperture 20 in register with the hole. A bolt 21 is inserted in each hole.18 and aperture 20 to join them together.

For fixing the filtering partition 5 to the basket 1 all that is required is to introduce the filtering partition in the basket so that its lid 7 rests on the supporting surface 2 of the basket, to orientate the filtering partition relative to the basket s6 that the holes 20 in the bridges 19 are in register with the holes 4 in the wall 3 on the edge of the basket and to push the bolts 21 into the holes 4. After these simple operations the filtering partition 5 will be found to be firmly fixed to the basket 1.

To release the filtering partition 5 from the basket 1 it is necessary only to take the bolts 21 out of the holes 4.

To facilitate the extraction of the bolts 21 from the holes 4 it is possible to provide a pin on the top of the rib 17, corresponding with each bolt, on which a suitable key with an eccentrically mounted disc on the bottom can be engaged.

This facility of connecting and disconnecting the filtering partition and the basket makes the fixing arrangement according to the invention very advantageous both for use in centrifuges with unloading from the base and in those with unloading via the top.

However, in order to be able to make full use of this advantage in centrifuges with unloading from the base it is expedient, and this constitutes a further characteristic of the present invention, to abandon the conventional design of such cenrifuges which envisages a permanent closure at the top of the centrifuge, and to adopt a design with a cover which can be opened.

Such a design is shown in Fig 1, in which it can be seen that a cover 24 is hinged at 23 onto the external housing 22 of the centrifuge.

In Fig. 5 a centrifuge like that shown in Fig.

1 is shown schematically on a smaller scale, with the cover 24 open and with the filtering partition 5 lifted up out of the centrifuge by means of a lifting device of which only the hook 25 can be seen.

It is thus possible to clean all .he inside of the machine and to introduce the cleaned filtering assembly (or a new one) once more, so that the machine continues its work while the removed filter is cleaned and replaced at leisure.

It should be emphasised, moreover, as already mentioned, that the filtering screens may be replaced rapidly by removing the locking rings 10, 10' and re-loc':ing them after having inserted the new clean screen.

These rings are very important because they have to provide a perfect holding for the screen to prevent the loss of the substance, which is sometimes very expensive.

Due to the expedient of having made the cover 24 so that it can be opened, the further advantage is obtained that, in addition to the filtering assembly 5, it is possible to remove and to carry away to the outside the basket 1 of the machine as well, in an operation which is sufficiently simple and rapid, so that it is possible to clean all the inside of the machine and the inside and the outside of the removed basket.

It is also possible to clean all the inside of the machine by shutting the lid 24 again and connecting readily, by means of quick connections, an appropriate device for hydrodynamic cleaning at high pressure, with which the cenrifuge has been provided, thus effecting extremely thorough total cleaning of the machine so that there are virtually no areas left with traces of residual substances.

As already mentioned, the use of a basket and a filtering partition of the kind described is also advantageous for the normal centrifuges without unloading from the base but which have a suction scraper blade, that is, which are equipped with blades which scrape off the solids and transport them pneumatically out of the machine through a central bore.

The described system for fixing the filtering screen to the lid of the filtering assembly may be used besides for filtering partitions formed by a simple fabric filter, also for those filtering partitions which comprise a perforated metal sheet mounted on the fabric.

In Fig. 4 in fact the arrangement for fixing a filtering element comprising a screen 6 and a perforated metal sheet 26 to the lid of a filtering assembly 5 is shown. In this version the angular profile 9 has a supplementary flange 27 and the edge 28 of the perforated metal sheet 26 is staggered with respect to the rest of the metal sheet and is locked between the said flange 27 and the locking ring 29. A rod 30 is used for positioning during the pre-mounting of the metal sheet and the screen. There is a certain number of such rods, distributed around the circumference.

While but two embodiments of the invention have been shown and described, it is obvious that a number of changes and modifications can be made without departing from the scope of this invention.

Claims (5)

1. An arrangement for fixing the filtering partition to the basket in a centrifuge; characterised in that is comprises an upper annular lid to the underneath of which the filtering screen is fixed and from the top of which there projects a circular rib which is coaxial with the lid and is provided with a plurality of radial holes, a plurality of bolts passing through the holes in a radial direction and having an abutment engaging the lateral internal surface of the rib, and an upper edge of the basket having an annular surface for the lid of the filtering partition to rest on and a cylindrical wall projecting upwards from the annular supporting surface and provided with a plurality of radial holes which are equal in number to the radial holes in the circular rib on the lid and are adapted to be brought in register with the latter holes so as to be engaged with the bolts.

2. An arrangement according to Claim 1, characterised in that the filtering screen is fixed to the lid and to a base on the filtering partition by means of a split ring which is adapted to be set under tension so as to press one edge of the screen against a flange of an angular profile projecting coaxially from the surface of the lid and the surface of the base respectively, thus locking the edge of the screen in place.

3. An arrangement according to Claim 2 with a filtering screen formed of a combination of fabric and a perforated metal sheet, characterised in that the upper and lower edges of the sheet are staggered with respect to the rest of the sheet and are locked between one flange of the respective angular profile and a locking ring.

4. An arrangement according to any one of Claims 1 to 3, used in a centrifuge with unloading from the base, characterised in that the centrifuge has a cover which can be opened.

5. An arrangement for fixing the filtering partition to the basket in a centrifuge constructed and adapted for use substantially as herein before described with reference to, and as shown in the accompanying drawings.