GB2340768A - Rotary drum filtration apparatus - Google Patents

Abstract

A rotary drum apparatus comprises a rotary drum 1, an end inlet 15, a receptacle 8 for collection of separated solids falling from the interior wall of the drum and means into which clarified liquid drains. Preferably a filtering medium or cloth 10, which can be supported by permeable material such as a gauze 100, forms the periphery of the rotary drum. The clarified liquid can drain into a tank 3 from which the drum can be mounted. Magnetic means exterior of the drum, which can comprise a series of magnets (6, figure 4), or an upstream magnetic drum may be used to separate magnetic/ferrous solids. Gravitational removal of the solid from the walls can be assisted by a scraper (7, figure 4) and/or brush 12 which may be attached to the receptacle 8 or by longitudinal blades 101 which are fixed within the drum. The receptacle 8 may comprise a removable tray or a trough containing an Archimedian screw (88, figure 9) which may be co-axial with the drum 1. The rotary drum may operate in combination with a further finer filtration drum 1a. The drum may be used for machine liquid coolant filtration.

Description

2340768 TITLE: FILTRATION APPARATUS

This invention relates -to filtration apparatus or units primarily, but not exclusively, for machine tool liquid coolant filtration. It is also capable of use in various fields where contaminants in liquids or similar fluids can be removed byfiltration.

The object of the invention is to provide improved and highly effective filtration apparatus which avoids the defects and disadvantages of known filtration units or very considerably minimises them. Practical advantages in these and other respects will be apparent from the subsequent description with reference to Figures 1 to 11.

There is a wide range and variety of filtration units available, created largely by their numerous defects and compromises thus making a choice of a suitable unit difficult by virtue of such inherent faults. Most units have a filtering element referred to as the "media" which usually has to be discarded as it is used. Such media, e.g. paper, usually renders the contaminant or swarf non-reclaimable.

In order that the above situation may be appreciated reference is firstly made to several prior 15 art filtration units as per Figures A to G of the accompanying drawings in which the advantages and disadvantages are set out. Like parts are designated by the same reference 0 letters in Figures A to F.

For simplicity the terms "dirty or clean coolanC and "swarf' are now employed but, as appropriate, are to be regarded as including any suitable liquid or like fluid, requiring 20 filtration of substantially solid matter from it such as swarf, sludge, debris or the like.

Weir type Ifiltration tank - Figure A This is the cheapest type of filtration unit in which a tank a is divided into a series of settlement compartments h by weirs c. Dirty coolant from a machine tool is discharg ed at d 2 into the first compartment b for deposit of swarf therein and the coolant flows over the weirs c and under baffles ba into successive compartments with reducing deposit of swarf until the final compartment receives substantially clean coolant for return to the machine tool by a 1 pump e. Filtration units of this kind are unsatisfactory as regards operation and maintenance.

Advantaees:- (a) Cheap, (b) No media, (c) Swarf recyclable.

Disadvantages:- (a) Poor filtration, (b) Difficult to clean.

Paper Roll Filters - Figure B These are the most common type of filtration unit in which a paper media f is fed from a supply rollg over a tank h and into a waste bin k. As the paper f passes over the tank h dirty coolant is discharged at d onto it trapping the swarf and allowing clean or clarified coolant to pass through into the tank h from where it is returned to the machine tool by a pump g. As the paper f becomes clogged or "blind" with swarf it is fed forward from the roll S to the bin k. The puddle of dirty coolant on the sagging paper f is shallow consequently the paper area has to be large so that the floor space entailed is large. Various grades of paper enable a high degree of filtration to be obtained but in use the particular grade remains fixed.

Advantages,:

(a) Good filtration.

i 3 DisadvantaRes:- (a) Requires paper media, (b) Shallow puddle, (c) Large paper and floor area, (d) Swarf is 1 mixed with discarded paper and is thus difficult to recycle (e). There can be overflow of dirty coolant at the side edge of the paper media.

Hydrostatic Filters - Fip-ure C These units again have a paper roll media f but it is fed through a deep bed 1 which creates a deep puddle and thus reduced floor.space. Otherwise the mode of operation is similar to the paper roll filter of Figure B. AdvantaRes:- (a) Good filtration, (b) Deep puddle, (c) Reduced floor space.

Disadvant-a-izes.- (a) Requires paper media (b) Swarf is mixed with discarded paper (c) Seepage of dirty coolant passed the paper edges may occur.

CentrifuRal Filters --Fieuj:e D These units basically comprise bowls n that are rotated at high speed about their vertical axes. Dirty coolant is discharged at d into the bowls n and the swarf is centrifuged against the inner 1 wall of each bowl and under an upper lip of the wall. The bowls 12 are driven by a motor drive M. Clean coolant flows out over the upper lipped edges of the bowls down into a lower 0 collecting tank h for pumping back at g to the machine tool. A media is not employed but the bowls n require manual cleaning.

4 Advantages- (a) No media, (b) Swarf recyclable.

1 - Disadvantaggs:- (a) Limited filtration, (b) Manual cleaning of bowls, (c) Expensive precision highly stressed 5 operating mechanism.

Z> Hydro Cyclone Filters - Figure E In these units the discharging dirty coolant at d enters a tank a and is pumped at 12 from the latter to the top of a V-form or Venturi shaped cyclone y in which it swirls downwardly with a cyclonic action. This causes the swarf particles to be thrown against the inner wall of the cyclone for discharge into the tank g whereas the clean coolant rises to the top of the cyclone for return at r to the machine tool.

Advantag ges:- (a) No media, (b) Recyclable swarf, (c) Continuous cycle.

DisadvantaRes:- (a) Limited filtration, (b) Swarf wears the cyclone, (c) Can require expensive swarf removal mechanism, (d) Usually requires three tanks.

Disc Filters - FiRure F In these units the dirty coolant discharge d is pumped at 12 from a receiving tank g to a series 0 of filter cloth discs w mounted on a perforated hollow shaft X. The dirty coolant passes throuo-,h the discs w which collect the swarf and the clean coolant passes into the hollow shaft X for return to the machine tool. Swarf is removed by a separate cycle from the discs w- by a centrifugal action on rotating the discs 3y at high speed by a motor drive y. The discs 3y may be also Pack flushed with clean coolant.

AdvantaRes:- (a) No media, (b) Recyclable swarf, (c) Good filtration.

DisadvantaRes:- (a) Expensive precision highly stressed operating mechanism. (b) Filtering cycle not continuous. (c) Elaborate cycle.

Magnetic (Magna) Drums - Figure All the previously described prior art filtration units are capable of being fitted with a "Magna Drum" as a pre-filter for ferrous material or swarf and are often so fitted. In use the drum D is rotated about its axis at a slow speed (e.g. 3 rpm) usually by a motor through a worm and worm wheel drive. Magnetic means, such as a series of bar magnets M is provided within the drum D. Dirty coolant is passed in a chute C under the drum D and the magnets

M attracts the ferrous swarf from the coolant to the exterior peripheral face of the drum D to which it adheres. As the drum rotates the swarf is brought to the top of the drum periphery where it is scraped off by an inclined fixed non-magnetic blade B and from which it slides off downwardly into a collecting receptacle R.

As currently used the drawbacks of a Magna Drum are as follows:- 1 It requires a separate motor drive additional to other motor drive or drives of the main filtration unit.

6 2. The chute C under the drum D has a fixed size of aperture or channel. If dirty coolant is supplied as "rated" to the chute C the drum D operates reasonably well. If excess coolant is supplied it overflows from the chute C. On the other hand if a reduced rate flow occurs then the dirty coolant runs clear of the lower periphery of the drum so that the magnetism of the magnets M largely or wholly becomes ineffective in attracting swarf from the coolant to the drum periphery. However, Magna drums perform an important role in reducing the amount of general debris for removal by the main filtration unit and are widely used.

In contrast to the above mentioned pior art filtration units and according to this invention a filtration apparatus or unit comprises at least one rotary drum arranged to be driven about a substantially horizontal axis, said drum having an end inlet for entry of contaminated liquid such as coolant into the drum, the internal periphery of the drum being arranged or adapted to take up contaminant such as swarf or the like from the contaminated liquid or coolant therein to an upper part of the drum as the latter rotates for obtaining gravitational and/or 15 assisted removal of the contaminant or swarf therefrom into a collecting receptacle positioned within the drum, provision being included for drainage of the cleaned or clarified liquid or coolant from the drum for return use or for any further filtration prior to such use.

As a main rotary filtration drum its periphery may essentially consist of a suitable peripheral filtering medium or cloth for taking up contaminant or swarf from the contaminated liquid 20 or coolant received in the drum to the collection receptacle, the clean or clarified liquid or coolant draining or passing through the lowermost part of the filtering medium or cloth as ID the drum rotates for return use or for further filtration prior to such use.

Usually as an additional Magna drum to a main filtration drum, the periphery of the Magna drum includes, or is adjacent to, magnetic means for the attraction of magnetic or ferrous contaminant or swarf against the internal periphery of the drum for taking up said contaminant or swarf from the contaminated liquid or coolant received in the drum to the collecting receptacle, cleaned or clarified coolant then draining from the drum, usually for further filtration by the main drum.

7 Combinations of successive drums may be co-axially arranged for driving by a common driving motor.

In practical examples of filtration apparatus or units in accordance with this invention reference is made to the further accompanying diagrammatic drawings in which:- Figures I to 3 are perspective views each showing differing schematic arrangements of filtration units with protective cover or housing removed; Figure 4 is a detail cross sectional view of a magnetic filtering drum (Magna drum); Figure 4A is a detail cross sectional view of an alternative form of magnetic filtering drum; Figure 5 is a cross sectional view of a main filtering drum, clean filtrate tank, and housing; Figure 6 is an axial plane section of a Magna drum, main filtering drum, clean filtrate tank and housing; Figures 7, 8 and 9 are sectional views similar to Figures 4, 5 and 6 but showing a further arrangement of contaminant or swarf collection and disposal or retrieval.

Figure 10 is a cross sectional view of a main filtering drum showing further developments, and Figure 11 is an axial plane section of a drum assembly including a further filtering drum.

8 Like or associated parts are referred to throughout the above Figures by the same or similar reference numerals whilst Figures 4 to 11 are on a larger scale than Figures 1 to 3. Also in the drawings sWarf is indicated by the reference SW, dirty coolant by the reference DCO and clean or clarified coolant by the reference CCO, and coolant puddle by the reference PU. In certain Figures appropriate direction of drum rotation is indicated by an arrow which direction may be clockwise or anti-clockwise.

Referring to Figure 1 a basic arrangement of the filtration unit is shown in which a rotary drum 1 having a periphery carrying a suitable filtering medium such as a filter cloth 10 or fine gauze, is rotatably mounted abouta substantially horizontal axis, over and partially into a lower tank 3.

In use swarf laden or dirty coolant, e.g. from a machine tool, is admitted into the drum 1 through a central or co-axial inlet opening 15 for filtering of the swarf from the coolant by the filter cloth 10 as the drum 1 is continuously rotated at a slow speed (e.g. 3 rpm -or thereabouts). Clean coolant passes or drains into the tank 3 through that part of the filter cloth 10 that is lowermost as the drum rotates. Details of the filtering action are later described whilst any suitable drum rotation speed may be employed.

The drum 1 is shown driven by a motor 5 through a worm and worm wheel drive 16 (Figure 6) or other suitable drive within a easing 19. A motor driven pump 4 on the tank 3 returns the clean or clarified coolant to the machine tool for further use.

In a more usual and typical arrangement of the filtration unit shown in Figure 2 a magnetic or Magn 0 g a drum 2 is included in front of the main filtering drum 1 and co-axial therewith i.e. between the latter and the driving gear casing 19. The exterior periphery 20 of the Magna drum 2 is provided with a continuous series of magnets 6 of bar or rod form secured to it in an axially parallel manner. As shown in Figure 2 the magnets 6 may be spaced apart or 25 contiguous as shown in Figure 4. The periphery 20 of the drum 2 may be of magnetic or non-magnetic material.

9 Dirty coolant is first admitted into the Magna drum 2 through the inlet opening 15 for magnetic removal of ferrous swarf and then passes into the main drum I for. filtering out of non-ferrous and any remaining ferrous matter. Both the Magna drum 2 and the main filter drum I are driven about their common horizontal axis by the same motor 5 and driving gear 5 16.

A development is shown in Figure 3 in which a ftirther co-axial filter drum I a is included and which may provide a finer degree of filtration than the drum I i.e. to provide coarse and fine filtering. Here again the three drums are driven together by the motor drive 5. Any suitable C) number of filter drums may be provided and driven in this way.

Referring to Figure 4, dirty coolant admitted into the Magna drum 2 flows or gravitates to the lowermost interior part of the drum 2 during its rotation and ferrous swarf in the coolant is attracted therefrom by adjacent magnets 6 and magnetically adheres or clings to the interior peripheral wall of the drum 2. As the drum rotates the swarf is taken up to a then upper part of the drum clear of the coolant where it may be removed by a fixed scraper blade 7 and directed by it into a receptacle or tray 8 centrally situated within or extending into the drum 2. The scraper blade 7 is shown carried in an inclined manner for this purpose by a guide flange 17 of a supporting slideway 9 receiving the tray 8. A pair of inclined-guide flanges ID 17 are shown provided by the slideway 9. However such a scraper blade 7 and guide flanges 17 may not be necessary as shown in Figure 4A.

Depending on the nature of the ferrous swarf some or all of it may fall by gravity from the 1.

drum wall into the tray 8 but the provision of a scraper blade 7 can be included to ensure removal and to direct the swarf into the tray. Swarf removal may be also effected or assisted by locally eliminating the effect of the magnets or causing repulsion i.e. by changed polarity I at the upper part of the drum.

In an alterative arrangement for this purpose the drum 2 may be rotatable within a fixed ring or partial ring of the magnets which ring is incomplete or gapped especially at its upper part or may have' an eliminating or repelling action so that the magnetic effect ceases or changes at the upper part of the rotating drum 2 and so allows or causes the swarf to fall away from 5 it.

Thus referring to Figure 4A a non-rotatable series of magnets 6a in a part circular or substantially semi-circular arrangement is closely and concentrically disposed about the outer periphery 20 of the rotary dram 2. The arrangement is such that in particular that part of the drum periphery 20 which is uppermost during rotation is clear of the magnets 6a so that ferrous swarf taken up by magnetic attraction from the coolant is able fall from the upper interior of the drum 2 into the tray 8. Since magnetic attraction is only required at the lower part and one side extent of the rotating drum 2 (i.e. at the left hand side for the direction of rotation indicated in the example shown), the magnets 6a are also omitted as unnecessary at the opposite (right hand) side. As shown the series of magnets 6a extends for 180" or thereabouts and terminates at each end on a diameter at approximately 45 0 to the horizontal. However these angular values may vary according to practical requirements.

Having regard to any eccentricity of rotation of the drum 2 and to ensure that the magnets 6a remain as closely as possible to the drum periphery 20 for maximum magnetic attraction effect, the series of magnets 6a is urged such as by spring loading towards the drum periphery 20 but prevented from actual contact with it. In the example shown the series or array of magnets 6a is carried by a shoe 60 pivotally mounted from a support structure 61 by a link 62 which latter is spring loaded by a tension spring 63 connected between the link 62 and a bracket 64 on the support structure 61. The shoe 60 is provided with rollers 66 which contact the drum periphery 20 to maintain the close clearance of the spring loaded magnets 6a from the periphery. The drum wall is preferably non-magnetic to avoid any magnetic braking action on the drum 2 as it rotates and also avoid build up of residual magnetism in the drum wall.

Any suitable magnetic means including electro-magnetic means may be employed on or about the drum 2 to provide magnetism or a magnetic field of appropriate strength.

The now relatively clean coolant passes from the Magna drum 2 into the main filter drum I and referring to the latter its periphery is perforated or of open framework construction and receives about it a closely fitting sleeve of a filtering medium or cloth 10 secured to the drum periphery in a fluid tight manner against edge leakage by annular clips or bands 11.

The drum I is shown of larger diameter than the Magna drum 2 and conveniently part of a unitary structure incorporating both drums. In particular the larger diameter of the main drum 1 provides at its lowermost part during rotation a deep bed 13 in which a deep puddle PU of coolant can be maintained for filtering out of non-ferrous and any ferrous swarf and any other contaminants as the coolant passes under gravity through the filter cloth at the lowermost part of the drum into the tank 3 and in a clean or clarified condition for pumping back to the machine tool.

As the main drum rotates the mainly non-ferrous matter clings to the filter cloth 10 and is carried by the then upper part of the drum clear of the coolant to fall by gravity into the tray 8. To ensure removal one or more fixed scraper blades or brushes 12 may be provided in contact or close proximity with the cloth 10 to positively dislodge swarf or other matter from it for dropping into the tray 8. Also to ensure that the removed swarf or the like is received by the tray 8 the slideway 9 may further be provided with outwardly and upwardly directed lateral guide flanges 18 which direct the falling matter or debris into the tray. If desired suitable flanges of this kind may be carried by the tray 8. Here again such fixed scraper blades or brushes 12 and guide flanges 18 may not be necessary as shown in Figure 10.

The central tray 8 is shown extending into both the main filter drum I and the Mago a d in gn ru 2 and is slidably supported horizontally in the slideway 9 so that it can be withdrawn rearwardly from the drum I for periodic emptying and replacement.

Z:, 12 However for continuous removal of collected swarf or the like and as shown in Figures 7, 8 and 9 the central receptacle or tray is in the form of a fixed trough 80 of part or semi circular cross section nd receives an Archimedean screw 88 rotationally fast with the drum assembly 1, 2 and about the horizontal axis of the latter. The helical hand of the screw 88 is such that 5 as it rotates relative to the troug :,h 80 the collected swarf or the like therein is continuously propelled rearwardly to discharge into a bin 83 situated at the rear of the drum 1 or into a chute or onto a conveyor or other convenient means for disposal or retrieval of the swarf.

In a similar manner to the slideway 9 or tray 8, the trough 80 may be outwardly and upwardly flanged at 82 to catch swarf and like matter falling from the filter cloth 10 at the upper part of the drum 1 and directing it into the trough 80. Similar but shorter flange formation is shown at 81 in the Magna drum 2 where one upward flange or extension 81 is shown carrying a scraper blade 7 (Figure 7). Once again the flange formation 81 and blade 7 may be omitted as per Figure 4A where it is to be understood that a Maggna shown in that g drum Figure can be used in relation to a trough 80 and Archimedean screw 88.

1 Referring to Figure 10 and in a further development of the filter drum 1 and of any further filter drum 1 a, the filter cloth 10 is externally supported by suitable permeable material such as a sleeve of suitably rigid 100 gauze of coarser mesh than the filter cloth 10 so as not to unduly restrict the filtering action of the latter. In particular the gauze 100 supports the cloth 10 at that part of the drum 1 which is lowermost as it rotates.

Practical prototype tests have established that contaminants such as swarf in the dirty coolant tends to accumulate or become caked to the inner periphery of the filter cloth 10 as it is taken up by the cloth from the coolant to the upper part of the drum. Such caked contaminant or swarf then falls off the cloth into the tray 8 or trough 80 and this is assisted by the tendency of the cloth 10 to sag at the uppermost position and so cause the caked contaminant to break off and fall away. Dependent on the nature of the contaminant the use of scrapers 7 or brushes 12 may not be necessary.

13 As also shown in Figure 10 longitudinal blades 101 are provided for the collection of falling contaminant from the cloth 10 and for directing it into the tray 8 or trough 80. The blades 101 are rotationally fast with the drum 1 and are preferably suitably inclined. As shown on the left hand side extent of the drum I and according to the direction of rotation, a blade 10 1 first receive and collects falling contaminant or swarf which it then takes up to the uppermost part of the drum to assume a steeply inclined or generally upright position to discharge or tip the contaminant or swarf into the tray 8 or trough 80. As already mentioned and by such an arrangement the provision of flanging 18 to the tray 8 or at 82 to the trough 80 may not be necessary.

The blades 101 are connected between end walls of the drum I and may also serve to reinforce or strengthen the structure of the drum.

As regards the provision of a further fine filtration drum I a as per Figure 3 relatively clean coolant draining from the drum I is passed to the ftirther drum I a which operates in the same manner as the drum 1 in relation to appropriate extension of the tray 8 or Archimedean screw 15 trough 80, the coolant draining from the fine filter cloth of the further drum I a then passing 0 ID into the tank 3 for pumped return to the machine tool.

In a convenient arrangement for this purpose a transfer drum It (Figure 11) may be employed and is shown about the first filter drum I and coaxial with the further fine filtration drum 1 a so as to communicate with the latter. As before the whole drum assembly preferably includes a Magna drum 2 into which dirty coolant is initially fed for passage to the filter drum 1. The clarified coolant then drains into the lower part of the transfer drum 1 t from where it directly passes to the ftirther drum Ia. After fine filtration through the latter it then drains into the tank 3 for return use.

As well as in the Mag C gna drum 2 and main filter drum 1, the collecting tray, or in a similar 25 manner the Archimedean screw trough 80, also extends through the finiher fine filtering drum Ia.

14 Although not shown in the diagrammatic drawings suitable fixed support structure is provided for the tray 8, slideway 9 and trough 80 and for the fixed scraper blades or brushes 12 in the upper part of the drum 1 and in any further drum I a. Likewise suitable bearing support is provided for the rotary drum 1 or for any of the various drum assemblies and/or 5 such drum or drum assembly may be carried by lower roller support e.g. in or on the tank 3.

In Figures 5, and 6 and 8 and 9 a cover or housing 14 is provided for the filtering apparatus or unit especially for the protection of the exterior of the filter cloth 10 and any gauze 100. The housing 14 is shown supported on the tank 3.

For complete single motor operation the coolant return pump 4 may be also driven through C> suitable gearing by the motor 5.

As well as its simple, compact and inexpensive construction and avoidance of the drawbacks of known filtration units as already referred to, the filtration apparatus or unit according to this invention provides several notable practical advantages as follows:- (a) The filter drum or drum assembly is only required to rotate at a low speed so that high precision construction is not entailed nor high stress operation. - (b) A single motor drive to the low speed filter drum or especially to both or all the 1 drums of a drurn assembly and any Archimedean screw mechanism is provided which, together with coolant return pump motor operation, only entails low electrical or other energy consumption.

(c) Especially in view of its economic low speed and non-stressful operation the filtration apparatus or unit is capable of a long serviceable life with minimal maintenance.

(d) The filter drum and especially the Magna drum can receive contaminated coolant over a wide range of flow rates in contrast to the limited flow rate of.known Magna drum's (see reference to Figure G). (e) The sleeve of filtering medium or cloth about the main filter drum and about any such 5 further drum is capable of continuous use over a long period and its fluid tight attachment to the drum is such that edge over flow, seepage or leakage of coolant bypassing the filter cloth is avoided or very minimal.

(f) The arrangement whereby swarf or the like is received from the interior of the drum filter cloth by a removable collecting tray or Archimedean screw trough enables the 10 swarf to be efficiently and often cleanly retrieved for recycling.

Whereas practical forms of filtration apparatus or units according to this invention have been herein described, it is to be understood that various modifications such as drum arrangements or combinations can be made with the scope of the invention herein defined and claimed.

Claims (1)

16 CLAIMS

1. Filtration apparatus or unit comprising at least one rotary drum arranged to be driven I about a substantially horizontal axis, said drum having an end inlet for entry of contaminated liquid such as coolant into the drum, the internal periphery of the drum being arranged or adapted to take up contaminant such as swarf or the like from the contaminated liquid or coolant therein to an upper part of the drum as the latter rotates for obtaining gravitational and/or assisted removal of the contaminant or swarf therefrom into a collecting receptacle positioned within the drum, provision being included for drainage of the cleaned or clarified liquid or coolant from the drum for return use or for any further filtration prior to such use.

2. Filtration apparatus or unit according to claim 1 wherein the periphery of the rotary drum consists essentially of a suitable peripheral filtering medium or cloth to the internal periphery of which contaminant such as swarf or the like is able to adhere or cling for taking up therewith from the liquid or coolant within the drum to a said upper part of the drum as it rotates for obtaining said gravitational and/or assisted removal therefrom into the collecting receptacle, and whereby the cleaned or clanified liquid or coolant is able to drain or pass through that part of the peripheral filtering medium or cloth which is lowermost as the drum rotates for said return use or for any further filtration prior to such use.

3. Filtration apparatus or unit according to claim 1 or 2 wherein contaminated liquid or coolant received within the rotary drum is arranged to accumulate as a puddle in that part of the drum which is lowermost as the drum rotates for takin. up contaminant 0 such as swarf or the like by the drum internal periphery from said puddle prior to drainage of the cleaned or clarified liquid or coolant from the drum.

4. Filtration apparatus or unit according to claim 2 or 3 wherein the periphery of the structure of the rotary drum is perforated or of open framework construction and receives thereabouts a sleeve of a suitable filtering medium or cloth which is secured 17 in a fluid tight manner to the drum against edge leakage from between the sleeve and drum.

5. Filtration apparatus or unit according to claim I wherein the exterior periphery of the rotary drum includes, or is adjacent to, magnetic means for the attraction of magnetic or ferrous contaminant such as swarf or the like against the internal periphery of the drum from contaminated liquid or coolant within the drum so as to take up said contaminant or swarf from the liquid or coolant to an upper part of the drum as the latter rotates for obtaining said gravitational and/or assisted removal from the internal periphery of the drum into the.collecting receptacle, the cleaned or clarified liquid or coolant then draining from the drum for return use or further filtration prior to such use.

6. Filtration apparatus or unit according to claim 5 wherein the magnetic means comprises a series of magnets about the exterior periphery of the drum.

7. Filtration apparatus or unit wherein a rotary drum having magnetic means according to claim 5 or 6 is arranged to operate in combination with at least one further rotary drum having a peripheral filtering medium or cloth according to claim 2, 3 or 4 ID C whereby liquid or coolant mag netically cleaned or clarified in the first mentioned drum is arranged to pass into said further drum for further filtering thereby and I I drainage therefrom for return use or for any still further filtration prior to such use.

1 8. Filtration apparatus or unit wherein a rotary drum having a peripheral filtering medium or cloth according to claim 2, 3 or 4 is arranged to operate in combination with a further similar rotary drum or drums for effecting further filtration of the liquid or coolant such as finer filtration prior to return use of the cleaned or clarified liquid or coolant and with, or without, the operative combination of a rotary drum having magnetic means according to claim 5 or 6 with said first mentioned peripheral filtering drum i.e. in the manner claimed in claim 7.

18 9. Filtration apparatus or unit according to claim 7 or 8 wherein the rotary drums are co- axially and successively arranged for said operation in combination.

10. Filtration apparatus or unit according to claim 9 wherein the coaxial and successive arrangement of rotary drums are driven by a common driving means or motor.

11.Filtration apparatus or unit according to any of the preceding claims wherein gravitational removal of contaminant such as swarf or the like from the internal periphery of the upper part of the or each rotary drum. as it rotates is effected or assisted by fixed scraper and/or brush means positioned within the drum and arranged to operate against or close to said upper internal periphery as the latter moves past said means.

12. Filtration apparatus or unit according to claim I I wherein the fixed scraper and/or brush means is mounted from the contaminant or swarf collecting receptacle or from support means for the latter.

13. Filtration apparatus according to any of the preceding claims I to 4 or 7 to 10 wherein the interior of the or each rotary drum contains longitudinal blade means rotatable therewith for directing gravitational removal of contaminant or swarf from the internal periphery of the upper part of the or each drum as it rotates into the collecting receptacle.

14. Filtration apparatus according to any of the preceding claims 1 to 4 or 7 to 13 wherein the filtering medium or cloth is externally supported by permeable material such as gauze.

15. Filtration apparatus or unit according to any of the preceding claims wherein the In C) contaminant or swarf collecting receptacle consists of a removable tray for disposal or retrieval of the collected contaminant or swarf.

19 16. Filtration apparatus or unit according to any of claims 1 to 14 wherein the contaminant or swarf collecting receptacle consists of a trough containing a rotary Archimedean screw for effecting propulsion of the collected contaminant or swarf for I disposal or retrieval.

17.Filtration apparatus or unit according to claim 16 wherein the Archimedean screw is co-axial with the or each rotary drum and is driven therewith.

18. Filtration apparatus or unit according to any of the preceding claims wherein the contaminant or swarf collecting receptacle or tray or Archimedean screw trough C) extends so as to be common to two or more rotary drams.

19. Filtration apparatus or unit according to any of the preceding claims wherein the rotary drum or combination of such drums is rotatably mounted on a tank for drainage of cleaned or clarified liquid or coolant into the tank.

20. Filtration apparatus or unit when substantially as herein described with reference to any of the embodiments thereof shown in the accompanying drawings.