GB2052278A

GB2052278A - Fluid flow apparatus

Info

Publication number: GB2052278A
Application number: GB7937650A
Authority: GB
Original assignee: Individual
Current assignee: Individual
Priority date: 1978-11-11
Filing date: 1979-10-31
Publication date: 1981-01-28
Also published as: IT1119955B; IT7969184A0; FR2441415A1

Abstract

A fluid flow apparatus such as a mixer or pump having a shaft 11 which is rotatably mounted on a normally downwardly extending bearing arm by means of a bearing 17 which in use is located below the liquid surface 27 of, for example, liquid manure, characterised by the feature that the bearing is enclosed by a cover tube 2 and closed or sealed-off relative to the liquid free of sliding seal means. Further protection may be provided by a ball-like member 25 which retains the liquid level 28 within the ball lower than that on the outside. The shaft 11 may be hollow so that gas supplied at an inlet 22 can be fed to a ventilation device 13. <IMAGE>

Description

SPECIFICATION Fluid flow apparatus The present invention relates to a fluid flow machine or apparatus having a shaft which is rotatably mounted on a downwardly guided bearing arm by means of a bearing located below the water surface.

Fluid flow apparatus of this type may be fashioned in many ways, for example, as pumps, stirring mechanisms, mixing mechanisms, ventilating devices and the like. In order herein to ensure a reliable guidance of a rotary element irrespective of whatever it is made, it is important that one of the bearings is located as closely as possible to this element. This is especially necessary for a rapidly rotating rotor element close to the bottom of a basin wherein it is necessary for a bearing to be mounted below the water surface relatively close to the rotor.

No particular problem will arise if lubricants are involved or at least if minimally polluted and noncorrosive liquids are involved. Even in this case, however, materials contacted by the liquid will in most cases be rapidly corroded and the accuracy of guidance diminishes after a short operating period.

In chemically corrosive and abrasive flowable materials such as liquid manure, flowing manure, effluent, sand sludge and the like, a low-lying mounting must always be screened on the outside in watertight manner. However, with materials available nowadays having sliding packings and other comparable kinetic sealing members, however, this is not readily possible, so that after a short operating period and above all in the case of highspeed shafts the sealing is broken and the bearing subjected to most corrosive action of the liquid and is thus damaged.

The object of the present invention is to provide a fluid flow machine or apparatus having a mounting located below the liquid surface in such a manner that this mounting is protected against the liquid free of sliding bearings.

According to the present invention there is provided a fluid flow apparatus having a shaft which is rotatably mounted on a normally downwardly extending bearing arm by means of a bearing which in use is located below the liquid surface, characterised by the feature that the bearing is enclosed by a cover tube and closed or sealed-off relative to the liquid free of sliding seal means.

Also according to the present invention there is provided a fluid flow apparatus for flowable material, such as liquid manure or liquidised manure contained in a basin having a suspension basin with an agitating mechanism which has a rotatably mounted connecting shaft for immersing in the liquid, and which connects a low-lying agitating element with a high-lying drive, in which the connecting shaft is tubular and formed as a gas supply pipe as an introduction member of a ventilating device.

In this manner it may be ensured that, from the low-lying rotor element to above the liquid surface, all components forming a mutual outer surface rotate as a unit at the same speed of rotation, whereby at least the internal bearing region is screened towards the outside by the cover tube.

Therefore, it is necessary only to ensure that the outer surfaces are accordingly made corrosionresistant whilst the internal components may be made of suitable materials. The complete screening leaves a free choice as to the method of mounting.

Therefore, operation at extremely high speed may be achieved without the mounting being substantially affected. It is only a question of cross-sectional dimensioning of the supporting mechanism of the mounting as to how far the bearing may be lowered.

In principle, the bearing may be lowered so as to be located to closely to the bottom of a basin of almost optional depth.

Conveniently a connecting shaft is guided from an elevated drive, and through a tubular bearing arm to a rotor element mounted at the bottom end thereof and below the bearing arm and liquid-tight with the tubular sleeve which projects from there to above the liquid surface. Thus, the drive may be passed internally downwards through a bearing tube made optionally rigid, and externally need be sealed off only by the cover tube, i.e. the cover tube to be mounted on the lower end of the connecting shaft must be sufficiently extended vertically upwards around the mounting. The connecting shaft may be mounted below in the bearing arm, or the cover tube may be mounted on the bearing arm and thereby supports the internal shaft.If driving torques are to be transmitted directly by the internal shaft, the connection to the cover tube has only to be powerful enough to be able to transmit inertia torques through the mass of the cover tube when starting-up and slowing down. If the cover tube transmits greater torques, thus at its circumference is fitted with conveyor blades or the like, it may be optionally connected to the connecting shaft-more especially in a form-locking manner.

The cover tube is expediently connected at its lower end - at least positively and especially detachably - to the connecting shaft and mounted on the bearing arm indirectly or directly by pivot bearings provided in the region of its two ends. The cover tube may thus be fashioned as a preferably cylindrical length of pipe of constant cross-section and secured at random to the connecting shaft and mounted on the bearing arm. It is only necessary to ensure that the connection to the connecting shaft is liquid-tight and sufficiently torque-resistant. In detachable couplings sealing may also be produced by abutment of metal surfaces.

According to a particular proposal of the invention, the lower pivot bearings have a bearing bush which is inserted between cover tube and internal shaft and secured against both by static sealing members with securing means. Thus, only this bearing bush as a separate component has to be provided with suitable connecting means without the cylindrical surfaces on bearing arm and cover tube being subjected to substantial actions. Also, the static sealing means may operate with rubber-like plastics materials as the protection for most liquids to be treated is to be regarded as adequate especially since it is possible to use different sealing means corresponding to the given liquids.

It is advisable to provide at least one of the two securing means with two sealing rings, more especially O-rings separated from each other by a spacing bush, which may be mutually braced axially by a tension device. In this manner the radial spacings between the three centrically interengaging parts may be reduced - which is often decisive for the applicability.

The protection of the mounting may be improved in that the upper edge of the cover tube has at least one screen associated with against splash liquid. A sealing against gas or vapour of the corrosive liquid is also desirable. Moreover, it may be advisable to accommodate a liquid absorbent, in a closed space of the cover tube, which then receives any condensation water which might possibly form.

Thus, a bearing sleeve may engage over the upper end of the cover sleeve in the manner of a ring cap and by means of the latter being non-rotatably secured to the lever arm and sealed by static sealing members.

Below the upper mounting at least one kinetic ring washer may be fitted around the cover tube.

The bearing bush and bearing sleeve are conveniently made as a whole from suitable bearing material, more especially non-ferrous metal.

In deviation from the aforesaid embodiment, the cover tube may also be closed cup-shaped at its lower end or connected integrally secure to the connecting shaft. In this manner the static sealing member otherwise to be provided at this point is prevented from being damaged. It is also possible to transmit considerable torques to the cover tube, so that it may at least be provided with a rotor element.

In principle it is possible to provide blades orthe like over the whole length of the cover tube, which may be connected to the connecting shaft with a special coupling.

The cover tube need not be integrally formed, but may be assembled from several sections, and the rotor element may have substantially any optional form and serve different purposes.

The cover tube is expediently supported on the bearing tube via the connecting shaft and a bearing mounted on the free end of the bearing tube, whereby resilient means are incorporated in the support. In this manner it is possible to utilize smaller dimensions for the lower bearing and axle deviations of the collaborating parts may be compensated by the resilient means - say a rubber seating ring.

It has thus been found expedient to connect the cover tube to the connecting shaft by at least an axially and radially resilient coupling - more especially a flexible coupling. The connecting shaft may in principle be given any suitable shape and needs to be led out only beyond the end of the bearing tube until connection with the cover tube.

The free end of the cover tube according to an alternative proposal may be connected to the rotor of a centrifugal pump - the housing of which is retained centrally by a support extended vertically to the bearing arm.

A further protection of the interior of the cover tube may be attained in that, between the upper end of the cover tube and the clamping of the bearing arm, a bell-like member is connected gas-tight thereto and encloses the end of the cover tube and extends downwards below it. If the liquid surface thereby rises above the lower edge of the bell acting as a "diving bell" member, then the airspace in this bell is sealed all around and is compressed with a further rise, i.e. the liquid surface inside the bell is substantially lower than that on the outside. For example, a flat securing flange may be fitted to the bearing arm, from which a bell tube is extended downwards centrically enclosing the cover tube.

It is, moreover, also proposed in accordance with the invention to introduce the rotor drive from the outside directly at the upper end of the cover tube.

According to a further proposal of the invention an internal shaft may be connected in special manner to its drive and rotatably mounted relative to the cover tube, and connected with its lower end to a rotor element independent of the cover tube. The cover tube may be used in this manner, for example, to drive an agitating element, with the internal shaft a pump or a ventilating member, i.e. the internal shaft may be used in turn to supply air or an agitation gas.

The cover tube and internal shaft may, for example, be driven by two oppositely orientated drive motors secured to different sides of the bearing arm.

They may, however, also be connected to a common drive motor by two different gear trains - one of which having at least one over-running clutch.

In a preferred embodiment of the invention, the bearing arm is mounted by a pedestal bearing with perpendicular spacing on the upper surface of a tank and the internal shaft connected to a discharge pump mounted on the tank bottom.

Fluid flow apparatus of the type described, are preferably used as agitating device for solving the problem, with a minimum of production expenditure whilst ensuring an optimal distribution of pressure gas in an agitating flow.

Afluid flow apparatus, for example, for flowable material stored in a basin or tank, such as liquid manure or flowing debris in a floation pool, having an agitating mechanism which has a rotatably mounted connecting shaft immersed in the liquid, which shaft connects a low-lying agitating element with a vertically lying drive, is characterised in accordance with the invention by the feature that the connecting shaft is tubular and adapted as a pressure gas supply pipe to an inlet member of a ventilating device.

According to a further configuration of the invention, the inlet member is mounted shortly in front of the closed end supporting the agitating element and on a part of the connecting shaft projecting freely from its mounting.

The development of the tubular connecting shaft for the through passage of gaseous agitating agent requires such a large diameter and therefore provides such a great bending resistance that for this alone it is economical in costs to extend the connecting shaft out of the bearing and for it to be unsupported over a certain distance. This projecting part may, without substantial expenditure, be formed as inlet member. The unit is thus shortened thereby and less bulky. Moreover, the distribution effect of the agitating agent is substantially improved. Since the agitating element conveys downwardly, which is normal in most cases, agitating eddies flowing downwardly and rotating centrally to the connecting shaft, forcibly carry along the radially emitted gaseous agitating agent and allows itto escape substantially uniformly to the side.The radial emission in the axial eddy first produces a fine distribution of the pressure gas, which thereupon reaches the direct interaction region of the agitating element so that it can be better distributed in the whole space of a liquid tank, e.g. for liquid manure or the like. It is necessary to ensure that gas can escape in a manner depending on its pressure.

In principle it suffices to provide the tubularwall of the connecting shaft in the region of the inlet members with evenly distributed apertures, with which, however, expediently separate introduction means are associated. These inlet means may be so formed as one-way valves in the manner of lip valves that they open only with internal pressure.

They may each be separately associated with each individual aperture, but are preferably adapted as a tubular sleeve gas-permeable under internal pressure. The gas under pressure may then issue intermittently from alternative nozzle positions of the cover circumference and is admixed and finely distributed with the liquid flow.

The tube cover, for example, may be formed by an assembly of ring discs made of rubber-like resilient material which are retained between end stops subject to limited external pressure. Thus, the ring discs may have an identical external diameter, but untrue central apertures - the inside width of which corresponds to the outer diameter of the connecting shaft. In this manner the ring discs may be adjusted somewhat relative to each other without losing the cylindrical sealing effect outwardly or without the flow connection interrupted internally.

At the ends the ring disc assembly may be defined by a sealing gaiter of angular cross-section and which is supported against a thrust ring of substantially rigid material.

It has been found advantageous to adapt the surface of the connecting shaft in the region of the inlet means and at least towards the end, to be a cylindrical smooth surface and the connection of the agitating element to be formed by friction contact clamping means.

To introduce the pressure gas in the region of the upper end of the connecting shaft, conveniently between the latter, a bearing tube enclosing it and two ring seals, a ring space is divided which communicates by radial openings on the one hand with the interior space of the connecting shaft and, on the other hand, with the pressure gas source.

The invention will be described further, by way of example, with reference to the accompanying semischematic drawings, in which: Figure 1 is a longitudinal section through an agitating device with an aerating or ventilating device for liquid manure pits forming an embodi ment in accordance with the invention; Figure 2 is a side view of a diagonal agitating device which is suitable for connection to the horizontal power take-off shaft of a tractor; Figure 3 is a schematic elevation of the apparatus of the invention used as a feed pump in the form of a plunger pump; Figure 4 is a side view, partly in section, of an agitating apparatus in which the cover tube has an external drive; Figure 5 is a modified embodiment of the ventilating device shown in Figure 4;; Figure 6 is a longitudinal section through a tank design having two separate drives by means of an internal shaft rotatable relative to the cover tube; Figure 7 is a plan view of the embodiment shown in Figure 6; Figure 8 is a schematic view of a fluid flow apparatus in accordance with the invention for stirring and ventilating liquid effluent or liquid manure in a liquid manure pit; and Figure 9 is an enlarged part section in two partial views 9a and 9b through the mounting of this apparatus.

In the fluid flow apparatus or machine shown in Figure 1 numeral 1 denotes a rotor element which is secured to a torpedo- or bomb-shaped cover tube 2, which in turn is rotatably retained by a tubular bearing arm 3 which is mounted in a pedestal bearing 4.

This pedestal bearing 4 has a base plate 5 which covers an opening 6 in the ceiling 7 of a suspension basin for liquid manure 8 or the like. The pedestal bearing 4 includes a drum 9 with inwardly directed flange 10 and is welded to the base plate 5. It may be welded at both ends to the bearing arm 3 or securely or detachably connected in any other manner.

Atubular connecting shaft 11 supports a driving pin 12 at its upper end which pin is welded-in for driving by a motor drive unit and is passed through the lower end of the cover tube 2 and at such point a T-shaped ventilating device 13 is connected. Such ventilating devices are known per se. They are generally provided with an air-permeable tube 14 which in most cases is formed by individual ring lamella e.g. of rubber which are held together by a tension rod 15.

The connecting shaft 11 is mounted at both ends of the bearing arm 3 by means of ball bearings 16 and 17. For mounting the cover tube 2 on the bearing arm 3 a longitudinal ball bearing 18 is used which is mounted on the upper end of the cover tube. In addition besides the rigid weld connection at the lower end with the connecting shaft 11 a further support is provided on this connecting shaft close to the bearing 17 by way of a rubber ring 19, which is mounted on a first disc 20 of a flexible coupling 21.

The resilient support 19 and 20 herein is more important than the coupling itself, since the drive connection occurs in any case at the lower end of the parts 2 and 11. Of importance, moreover, is the resilient centering close to the bearing 17. Three bearings 16,17 and 18 in all suffice. A resiliently yielding coupling as the Hardy or like flexible coupling 21, however, is of particular advantage when the connecting shaft 11 is not extended to the bottom, since the parts 2 and 11 receive a limited adjustability in this manner.

The introduction of air or the agitating gas is effected through a pipe socket 22 mounted in the bearing arm 3 and through radial openings 23 in the connecting shaft 11, whereby the lateral space of the bearing arm is sealed in gas-tight manner by sealing members 24.

On the underside of the base plate 5, a bell-pipe or tube 25 is welded centrally to the bearing arm and together with the base plate forms a kind of diving bell i.e. forms an outwardly closed ring space 26 in which the air is compressed with the rising liquid surface 27 - this inside liquid surface 28 thus remains substantially below the liquid surface 27 and is spaced to a progressively greater extent from the above end of the cover tube.

It may be expedient to reduce in size the included air space by compression. However, it appears more essential to protect the mounting also from vapours of the liquid 8. For this a further sealing member 29 may be provided above the longitudinal bearing 18.

In this manner any direct or indirect action of the liquid 8 on the mounting of the cover tube 2 with the rotor element 1 is stopped. At the most, condensation water could be formed by temperature changes in the interior of the cover tube, which, if necessary, may be avoided by charging with an absorbent In the event of operation without the ventilating device device, drying out and sealing may occur in the meantime by the tubular drive shaft.

Also according to Figure 2, the rotor element 1 is adapted as a liquid sc,-ew and mounted on the lower end of the cover tube 2. The upper end of the tube 2 is overlapped at this point by a ring cap 30 secured to the bearing arm 3. The ring cap 30 takes over the protection against liquid splashes and in turn can receive a sealing member corresponding to 29.

The upper part of the bearing arm 3 is securely clamped at this point in a pedestal bearing 41 by pipe clips 31, and the driving pin 12 may be coupled by a hinged coupling, in known manner, to the horizontal power take-off shaft of a tractor and which is connected from time to time to stir or agitate the contents of a liquid manure pit. In this embodiment and deviating from Figure 1, the connecting shaft 11 extends to close to the lower end of the bearing arm 3, thus no air is introduced.

According to Figure 3, the bearing arm 3 and a supporting arm 32 extending parallel therewith are clamped in a pedestal bearing 42 which also supports an electric motor 33 which may be adapted as a driving motor and is connected, via the clutch 34, to the connecting shaft 11 and, via the flexible coupling (not shown), to the cover tube 2. This cover tube supports at its lower end (in a manner not further shown) the impeller 36 of a centrifugal pump 40 securely mounted thereon at this point, whilst the pump housing 36 is secured to the supporting arm 32 which may also form an outwardly extended pressure pipe.

In accordance with Figure 4 only the bearing arm 3 is welded to the pedestal bearing 43 or may be securely or detachably mounted in any other manner. Here the drive motor 33 and coupling 34 and a reduction gear shaft 37, are retained with lateral spacing from the rotor axle 38 on the bearing arm 3.

The lower end of the reduction gear shaft 37 projects through a clearance aperture in the base plate 5 and is guided in an adjustable bearing 39 which is mounted securably displaceable on the base plate 5 at right angles to rotor axle 38. In this manner V-belts 45 of a belt drive with driving pinion 46 and belt ring 47 may be retensioned. Thus, the upper end of the cover tube 2 is directly driven. The latter therefore in addition to the axial bearing 18 needs only to be supported by a radial bearing 48 on the lower end of the bearing arm 3.

The whole belt drive is screened downwardly by a hood 49 secured to the underside of the base plate 5.

A sealing member 50 is also mounted at this point over the axial bearing 18 and, just like the ball bearing is covered by a ring cap 51 mounted on a bearing arm.

Apart from the drive, the whole structure of the fluid flow apparatus is fulfilled in two telescoped parts, namely the cover tube 2 and the supporting arm 3 with pedestal bearing.

Additional to or instead of a rotor element 1, such may be adapted as an agitating member in the embodiment of Figure 4 and an air supply for a ventilating device 13 may be provided in simple manner. In principle it is only necessary to provide a longitudinal bore in the bearing arm 3 and to close the lower interior space 52 of the cover tube 2 by a sealing member 53 provided between the tube and the bearing arm.

To render this sealing member adjustable, an adjusting tube 54 is mounted in the bearing arm 3, by means say in the form of a packing gland, and the lower outer flange 55 thereof acts on the sealing member 53. A nut 56 is screwed on a thread at the upper end of the adjusting tube which is supported against the upper end of the bearing arm possibly by means of a sealing ring or the like 57. In principle therefore, each tubular bearing arm 3 as shown in Figure 4, may be readily used without any further conversion for a ventilating device according to Figure 5, in that the cover tube 2 is merely replaced and the adjustment tube 54 with sealing member inserted.

In the embodiment shown in Figures 6 and 7 a combined fluid flow machine is mounted on a cylindrical tank 58 closed on all sides and is suspended from its tank bottom 59 and is a discharge pump 60 adapted as an eccentric screw pump having a further rotor element 61 as an eccentric screw. The eccentric screw is thus driven, via the articulated shaft 62 which the flexible heads 63, by an internal shaft 64 which is rotatably mounted within the bearing arm 3 by means of two bearings 65 and 66. This bearing arm is retained towards its upper end on the tank 58 by means of two pedestal bearings with perpendicular spacing thereabove.

The cover tube 2togetherwith the rotor element 1 is driven in identical manner as shown in Figure 4 by the driving motor 33 by means of a belt drive 46, 45 and 47. A further belt drive 46', 45' and 47' is used for driving the internal shaft 64. The discharge pump and agitating mechanism may be set in motion as desired.

This may also be achieved in that a driving motor 33 is provided with a second shaft end for the belt pinion 46' and by interposing an overriding clutch or a free wheel device. Clockwise rotation then causes the agitating mechanism to be operated whilst anti-clockwise rotation causes the discharge pump to operate.

For the discharge operation it is not essential for the agitating mechanism to stop. On the contrary, it may be favourable that mixing continues during the discharge operation. The rotor element 1 in turn may be operated in both directions of rotation without any disadvantages occurring. Therefore, in principle, a single overriding clutch will suffice in driving the discharge pump.

The invention has been described by way of only a few embodiments, but it may readily be related to other fluid flow machines or appliances having rotor elements revolving below the water surface and is particularly suitable for use in all liquids which necessitate the mounting being screened against the liquids.

In the fluid flow apparatus shown in Figures 8 and 9, a rotor element adapted as an agitating vane is denoted by numeral 1, and is securely mounted on the end of the tubular connecting shaft 11. The cover tube 2 engages around the lower end of the bearing arm and is rotatable at its upper end and sealed bracingly at its lower end relative to the connecting shaft 11. The connecting shaft 11 is passed through the lower end of the the cover tube 2 and forms a ventilating member 13 at the portion projecting from the cover tube to the rotor element.

A double ball bearing 16 is mounted between two ring sealing members 241 and 242 on the shaft end 12 for mounting the connecting shaft 11 in the bearing tube 3. A third sealing ring 243 is mounted below the latter sealing members and mounted with axial spacing. The ring space 71 formed thereby within the bearing arm 3 may be connected with a source for compressed air or any other gaseous agitating agent via the outwardly mounted pipe socket 22. The ring space 71 is connected with the interior of the connecting shaft 11 by means of several openings 23 in the bored enlarged lower end of the shaft end 12.

A bearing bush 72 made of a suitable bearing metal or bearing plastics material is clamped closely below the base plate 5 by means of a clamping ring 73 and screws 74 over two sealing rings 76 of rubberised material attached to two sides of a spacer bush 75 in such a manner that a limited radial and pivotal adjustment is possible without impairing the frictional connection or the sealing.

The upper end of the cover tube 2 projects from the bearing sleeve 72 and thereby forms the pivot bearing 77 adapted as a sliding bearing. The sliding bearing surface is closed downwardly by two series connected sealing ring 29 which check the spray liquid and vapours. The bearing may be lubricated via a grease nipple 78. The lower end of the cover tube 2 internally supports a bearing bush 80 located by means of pin or screw 79 and which in turn is made of non-corrosive bearing metal or a plastics material bearing. The sealing between the two detachably connected parts 2 and 3 is thus effected by sealing rings 81 let into the bearing bush.The bearing bush 80, by means of a clamping ring 82, screws 83, spacer bush 84 and sealing rings 85, is clamped onto the connecting shaft 11 in a similar manner as the bearing sleeve 72 on the bearing arm and encloses the lower end of the bearing arm 3 and forms a pivot bearing 86 therewith.

The cover tube 2, which is adapted as a detachable, cylindrical tube element, is hence clamped at its lower end, by means of two series-connected static sealing members 81 and 85, to the connecting shaft and thereby encloses the low-lying pivot bearing 86. The upper pivot bearing 77 on the other hand may be located above the liquid surface 27 with a constant perpendicular spacing and has only to be protected against spray liquid, which is readily taken over by the bell-shaped bearing sleeve 72 with its two sealing members 29. Driving torques or appreciable forces need not be transmitted by the cover tube 2 - this is performed exclusively by the connecting shaft 11 supported at both ends of the bearing arm 3.

The capacity to transmit the torque and the passing through of gaseous agitating means, necessitates a larger tube diameter and correspondngly great bending resistance of the connecting shaft.

The latter shaft may project freely, without the danger of overloading, by about at least tenfold its diameter and beyond the lower ends of the bearing arm and the cover tube in accordance with the spacing a. This section of the connecting shaft will be used herein to accommodate the ventilating member 13.

In this region, i.e. below the cover tube 2, as best seen from Figure 2b, the whole outer surface 87 of the connecting shaft is of smooth cylindrical form and its lower end is sealed gas-tight by a cover 88 welded thereon. The agitating element 1 is removably clamped by means of tapered sleeves 89, thrust ring 90 and screws 91.

The freely protruding part of the connecting shaft 11 may hence be used directly as introduction member for the agitating agent. For this purpose the shaft part is provided with uniformly distributed apertures 111, which may have suitable lip valves or differently adapted non-return valve elements associated therewith.

Herein, however, a ring disc assembly 92 is used as introduction means which has the same outer diameter 98 but is non-circular (e.g. square central apertures 94). These central apertures 94 have an inside width which corresponds to the external diameter 87 of the connecting shaft 11. Between the latter and the sleeve-shaped introduction means therefore several irregularly extending screw passages of somewhat varying cross-section are formed which, however, form flow connections throughout the whole length. The ring disc assembly therefore, if compressed in axial direction, may be subjected to internal pressure until the gaseous agitating agent escapes into the open. This "introduction pressure" is dependent upon the axial force acting between the ring discs.

At both ends of the ring disc assembly a cover sleeve 95 made of soft, rubber-like material like that of the ring discs, is mounted and is enclosed by a support ring 96 also of angular cross-section. The lower support ring 96 abuts against the rotor element 1 or its clamping, and the upper is retained by a pipe clip 97. By displacing this pipe clip along the connecting shaft 11 the abutment pressure acting between the ring discs 92 and thereby the internal pressure at which the introduction begins may hence be varied.

The operating pressure generally is at about 30 to 50% beyond the introduction pressure so as to ensure introduction of the agitating medium also with encrustation or other change of the forward passage.

The whole ring disc assembly thus acts in the manner of a large number of lip valves - some of which with the abutting operating pressure remain constantly open and others alternately open and close. In any case, a large number of continuous and intermittent radial jets of agitating medium are emitted from the ring disc assembly.

The rotating ring disc assembly is surrounded by a helical flow rotating in the same direction and which by development of the rotor element and direction of rotation is so formed that, on the one hand it has a different peripheral speed at the circumferential surface 98 of the ring disc assembly and, moreover, is downwardly directed parallel to the rotor axis 38 in the direction of the arrows 99. The radially outwardly emitted gas jet or gas bubbles are thus mainly deflected in an axial direction although partly, however, also in circumferential direction. By this means large gas bubbles are divided directly before the introduction operation. The smaller bubbles, moreover, on impact with the bottom of the tank are again subjected to a dividing stress and then spread to the side, so that a quite uniform gas agitation is obtained in the whole liquid.

Apart from the specific adaptation of the ring disc assembly, the additional expenditure herein resides in the apertures 111. This expenditure, however, is substantially smaller than the cost saving for the overall structure and, moreover, ensures a better distribution of the agitating medium.

Claims

1. A fluid flow apparatus having a shaft which is rotatably mounted on a normally downwardly extending bearing arm by means of a bearing which in use is located below the liquid surface, characterised by the feature that the bearing is enclosed by a cover tube and closed or sealed-off relative to the liquid free of sliding seal means.

2. A fluid flow apparatus as claimed in claim 1, in which a connecting shaft is driven by an overhead drive passing through the tubular bearing arm to a rotor element mounted below the arm and connected below the bearing arm liquid-tight with the cover tube, which tube from there projects to above the liquid surface.

3. Afluid flow apparatus as claimed in claim 2, in which the cover tube at its lower end is connected at least positively to the connecting shaft and is mounted, by means of pivot bearings provided in the region of its two ends, indirectly or directly on the bearing arm.

4. A fluid flow apparatus as claimed in claim 3, in which the lower pivot bearing has a bearing bush which is inserted between cover tube and connecting shaft and which is secured to both by static sealing members with securing means.

5. A fluid flow apparatus as claimed in claim 4, in which at least one of the securing means has two sealing rings, more especially O-rings, separated from each other by a spacer bush and which are adapted to be mutually axially clamped by a clamping device.

6. A fluid flow apparatus according to any of claims 1 to 5, in which the upper edge of the cover tube has at least one screen against liquid spray associated therewith.

7. Afluid flow apparatus as claimed in claim 6, in which a bearing sleeve engages over the upper end of the cover tube in the manner of a ring cap and by means of the latter is secured to the bearing arm and sealed by static sealing members.

8. A fluid flow apparatus as claimed in any of the claims 1 to 7, in which at least one kinetic ring sealing member is mounted below the upper mounting between the bearing sleeve and the cover tube.

9. Afluid flow apparatus as claimed in any of the claims 4 to 8, in which the bearing bush and the bearing sleeve is made conveniently as a whole of a suitable bearing material, such as non-ferrous metal.

10. Afluid flow apparatus as claimed in any of the claims 1 to 8, in which the cover tube is closed cup-shaped at its lower end or is integrally secured to the connecting shaft.

11. Afluid flow apparatus as claimed in claim 10, in which at least one rotor element is mounted on the cover tube.

12. Afluid flow apparatus as claimed in any of the claims 1 to 11, in which the cover tube is supported on the bearing tube via a connecting shaft and a bearing mounted on the free end of the bearing tube, whereby resilient means are incorporated in the support.

13. Afluid flow apparatus as claimed in claim 12, in which the cover tube is connected to the connecting shaft by an at least axially and radially flexible coupling such as a Hardy coupling.

14. A fluid flow apparatus as claimed in any of the claims 1 to 13, in which the free end of the cover tube is connected to the rotor of a centrifugal pump, the housing of which is retained on the cover tube centrically by a support extended upwards parallel to the bearing arm.

15. Afluid flow apparatus as claimed in claim 6, in which between the upper end of the cover tube and the clamping of the bearing arm a bell-shaped member is connected gas-tight which encloses all around the end of the cover tube and is extended to below this end.

16. Afluid flow apparatus as claimed in claim 15, in which a flat securing flange is mounted on the bearing arm and from which flange a bell-shaped tube centrally enclosing the cover tube end extends downwards.

17. Afluid flow apparatus as claimed in any of the preceding claims, in which the rotor drive is initiated from the outside directly at the upper end of the cover tube.

18. A fluid flow apparatus as claimed in claim 17, in which within the bearing arm an internal shaft connected in a separate manner to its drive is mounted rotatable relative to the cover tube and is connected at its lower end to a rotor element independent of the cover tube.

19. A fluid flow apparatus as claimed in claim 18, in which the cover tube and the internal shaft are adapted to be driven by two oppositely orientated driving motors secured on two different sides to the bearing arm.

20. A fluid flow apparatus as claimed in claim 18, in which the cover tube and the internal shaft are connected to a common drive motor by means of two separate gear trains, one of which at least being provided with an overriding clutch.

21. Afluid flow apparatus as claimed in claims 18, 19 or 20, in which the bearing arm is mounted, by means of a pedestal bearing with perpendicular spacing on the upper surface of a tank and the internal shaft is connected to a discharge pump mounted on the tank bottom.

22. A fluid flow apparatus for flowable material, such as liquid manure or liquidised manure contained in a basin having a suspension basin with an agitating mechanism which has a rotatably mounted connecting shaft for immersing in the liquid, and which connects a low-lying agitating element with a high-lying drive, more especially as claimed in any of the claims 1 to 21, in which the connecting shaft is tubular and'formed as a gas supply pipe as an introduction member of a ventilating device.

23. A fluid flow apparatus as claimed in claim 22, in which the introduction member is connected closely in front of the closed end supporting the agitating element on a part of the connecting shaft freely from its mounting.

24. Afluid flow apparatus as claimed in claim 23, in which the tubular wall of the connecting shaft in the region of the introduction member is provided with uniformly distributed apertures, which have separate introducing means associated therewith.

25. Afluid flow apparatus as claimed in claim 24, in which the introducing means has a tubular jacket which is gas-permeable only under internal pressure.

26. A fluid flow apparatus as claimed in claim 25, in which the tubular jacket is formed by an assembly of ring discs made of rubber-like flexible material which are retained under limited axial pressure between end stops.

27. A fluid flow apparatus as claimed in claim 26, in which the ring discs have the same external diameter but have non-circular central apertures, the inside width of which corresponds to the external diameter of the connecting shaft.

28. Afluid flow apparatus as claimed in claims 26 or 27, in which the ring disc assembly is limited at both ends each by an angular sealing sleeve which is substantially supported against a thrust ring of rigid material.

29. Afluid flow apparatus as claimed in any of the claims 24 to 28, in which the surface of the connecting shaft in the region of the introducing means and is cylindrical with a smooth surface at least towards the end and the connection between the agitating element is formed by frictionally engaging clamping means.

30. A fluid flow apparatus as claimed in any of the claims 24 to 29, in which in the region of the upper end of the connecting shaft between this a bearing tube enclosing it and two ring sealing members, a ring chamber is divided which communicates by means of radial openings with the interior of the connecting shaft and with the pressure gas source.

31. A fluid flow apparatus constructed and arranged to operate substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.