US3246882A

US3246882A - Apparatus for the aeration of liquids

Info

Publication number: US3246882A
Authority: US
Inventors: George F G Clough
Original assignee: Carves Simon Ltd
Current assignee: Simon Carves Ltd; Carves Simon Ltd
Priority date: 1963-02-22
Filing date: 1964-02-19
Publication date: 1966-04-19
Anticipated expiration: 1983-04-19
Also published as: BE644172A; CH411726A; DE1457131B1; GB1082342A; AT247803B

Description

April 19, 1966 G. F. G. CLOUGH 3,246,882

APPARATUS FOR THE AERATION OF LIQUIDS Filed Feb. 19, 1964 4 Sheets-Sheet 1 INVENTOR GEORGE FRnucls GILBERT CLOUGH FITTOFENEY April 19, 1966 CLQUGH 3,246,882

APPARATUS FOR THE AERATION 0F LIQUIDS Filed Feb. 19, 1964 4 Sheets-Sheet 2 INVENTOR GEORGE Freawcls GILBERT CLOUGH ATTORNEY April 19, 1966 e. F. G. CLOUGH 3,246,832

APPARATUS FOR THE AERATION OF LIQUIDS Filed Feb. 19, 1964 4 Sheets-Sheet s mvm-roe GEORGE FRANCIS GILBERT CLOUGH BY M April 19, 1966 G. F. G. CLOUGH 3,246,882

APPARATUS FOR THE AERATION OF LIQUIDS Filed Feb. 19, 1964 4 Sheets-Sheet 4.

Fig. 5.

Hi i I 1 mvamoe GEORGE. FReNcrs GILBERT CLOUGH HTTOENEY United States Patent 3,24%,882 APPARATUS FOR THE AERATION 0F LIQUIDS George F. G. Clough, Macclesfield, England, assignor t0 Simon-Carves Limited, Stockport, England, a British company Filed Feb. 19, 1964, Ser. No. 345,878 Claims priority, application Great Britain, Feb. 22, 1963, 7,160/ 63 11 Claims. (Cl. 259-135) This invention is concerned with improvements in or relating to the aeration of liquids.

In the aeration of a liquid using an aerator member, often the efliciency of aeration is dependent upon the level of the aerator member in the liquid. Liquid level often varies during aeration;

It is an object of the invention to provide improved liquid aeration apparatus.

Liquid aeration apparatus embodying the invention is described hereinafter with reference to the accompanying drawings; this apparatus comprises (a) a liquid c'on tainer, (b) a vertical shaft rotatable about its axis which is disposed centrally of the container, (c) an aerator member secured on the shaft for rotataion therewith in the container, said aerator member comprising an inverted symmetrical frusto-conical shell coaxial with the shaft, a circular cylindrical projection extending downwardly from the shell coaxially therewith, and a plurality of vertical planar arms extending from the periphery of the projection tangentially of the projection along the lower surface of the shell, (d) a motor, (e) a gear box the input side of which is connected to the motor and the output side of which is adapted to rotate the shaft, and (f) means for moving the aerator along the axis of the shaft while the shaft is rotating, said means comprising -(i) a differential gear mechanism which comprises a first set of two coaxial gear wheels one on either side of the axis of the shaft, being freely rotatable about a horizontal axis, and also being mounted for rotation with the shaft about the axis of the shaft and a second set of two coaxial gear wheels in mesh with the first set of gear wheels and freely rota-table about the axis of the shaft, (ii) a nut coaxial with, and mounted for rotation with, one wheel of the second set, (iii) a threaded spindle screwed into the nut, mounted for rotation with the shaft, and for up and down movement with the aerator member, (iv) means for restraining relative rotational movement of the gear wheels of the second set in the absence of substantial force urging such movement and permitting such movement when one or the other of said wheels is stopped, and (v) brake mechanism whereby rotation of one or the other of the gear wheels of the second set may be stopped to cause, as required, up or down movement of the threaded spindle and thus up or down movement of the aerator member.

There now follows a detailed description, to be read with reference to the accompanying drawings, of the liquid aeration apparatus embodying the invention. This apparatus has been selected for description by way of example of the invention only and not by way of limitation thereof.

In the accompanying drawings:

FIGURE 1 shows a side view, partly in section of parts of the apparatus;

FIGURE 2 shows a section on the line 2--2 of FIG- URE 1;

FIGURE 3 shows a section on the line 33 of FIG- URE 1;

FIGURE 4 shows a plan view of parts of the apparatus; and

FIGURE 5 shows a sectional front view of the appatus.

The apparatus comprises a tank 12 (FIGURE 5) in which liquid for aeration is contained, and an agitator member 38 which is rotatable in the tank 12 about a vertical axis to aerate the liquid; the axis being centrally disposed in the tank 12. The apparatus also comprises means for moving the aerator 38 up and down along said axis while it is rotating. The appartus may be used, for example, to aerate a liquid comprising an efiluent and containing aerobic bacteria adapted to treat the effluent for disposal.

The tank 12 has an inlet 13 and an outlet 15 for the liquid, and in the operation of the apparatus liquid fiows continuously from the inlet 13 through the tank 12 to the outlet 15. Secured to a supporting structure 14 which extends across the top of the tank 12 is a reduction gear box 16 having a horizontal input shaft 18 which is arranged to be driven by an electric motor 20 supported on the structure 14. The gear box 16 has a vertical output drive shaft 22 (FIGURE 1).

The output shaft 22 extends upwardly and downwardly of the casing of the gear box 16 and the gear box 16 is arranged on the supporting structure 14 so that the output shaft 22 lies substantially over the centre of the tank. The output shaft 22 has a passage 24 bored coaxially therethrough (FIGURE 3).

A rigid cylindrical tube 26 is secured to the lower end portion of the shaft 22 (FIGURES 1 and 3) by a key 28 which extends between a vertical keyway 30 in the tube 26 and a corresponding slot 32 in the shaft 22. Another similar rigid cylindrical tube 34 is bolted to the lower end of the tube 26 coaxially therewith. Two diametrically-opposed vertical kepways 36 (FIGURE 3) extend for the length of the

tubes

26, 34, being cut in the inner peripheries of said tubes; the keyways 36 are from the keyway 30. The agitator member 38 is secured to a vertical shaft 40 for rotation with said shaft. The shaft 40 is movable up and down along the keyways 36, having two diametrically-opposed vertical slots 42 cut in its periphery corresponding to the keyways 36 in the

tubes

26, 34; a key 44 is secured in each slot 42, these keys 44 being slidably engaged in the keyways 36.

The lower end portion of the shaft 40 is keyed in a driving boss 46 for the agitator member 38, a key 48 extending between a keyway 50 in the boss 46 and a slot 52 in the shaft 40. The shaft 40 is surrounded by a flexible corrugated tube 54 secured at one end to the lower end portion of the tube 34 and at the other end to the driving boss 46.

The upper end portion of the shaft 40 has a ring 55 secured thereto coaxially therewith; the ring 55 has a square inner periphery 56.

The agitator member 38 corresponds generally in construction and arrangement with the agitator member described in our copending US. patent application Serial No. 158,672 and now Patent No. 3,182,972, to which reference may be made. The member 38 comprises an inverted symmetrical frusto-conical shell 39 coaxial with the shaft 40, a circular cylindrical projection 41 secured to, and extending downwardly from, the shell 39 coaxially therewith, an inverted conical cap 37 closing the lower end of the projection 41, and a plurality of arms 43 each of which lies in a vertical plane and extends tangentially from the projection 41 along the lower surface of the shell 39. Each arm 43 has an end portion 45 extending outwardly from the outer periphery 47 of the shell 39. Each end portion 45 has a horizontal upper edge 49, and has a horizontal plate 51 which extends circumferentially from the edge 49 on the side of the arm 43 remote from the projection 41, and radially from'the outer periphery 47 of the shell 39. In the operation of the apparatus the member 38 is rotated in the sense in which the plates 51 extend circumferentially from the arms 43.

The driving boss 46 has a circular plate 66 secured thereto and the plate 61 is detachably secured to a fiat horizontal plate 62 extending across the interior of the shell 39 of the agitator member 38. In smaller sizes of agitator, up to, say, Z-feet diameter, the plate 60 may be secured directly to the fiat plate 62, as balancing difiiculties are then not of great importance. However, in larger diameters, adjustment means as shown in the drawings, are required to ensure an even balance. For this purpose, a tapered recess 64 is formed coaxially in the lower end portion of the shaft 40 and a hole 66 is formed in the plate 62 coaxially of the agitator 38. Four bolts 68 (only two of which are shown) extend upwardly through a ring '70 secured to the underside of the plate 62, through the plate 62 itself and through holes 71 close to the periphery of the plate 66; the bolts 68 are spaced evenly round the plate 60. Nuts 73 are screwed onto each bolt 68 above and below the plate 61). A steel ball 74 rests in the hole 66 in the plate 62 and the ball 74 is received in the tapered recess 64 to provide a fulcrum. By adjustment of the nuts '73, the agitator member 38 may be balanced on the shaft 40, about the fulcrum provided by the ball 74.

The means for moving the agitator member up and down comprisesa vertical spindle 72 (FIGURES 1, 2 and 3) which extends through the passage 24 in the shaft 22 and is movable up and down to move the agitator member 33 up and down. The spindle 72 is directly connected to the shaft 40, having a square formation 78 (FIGURE 3) at its lower end which engages in the ring 55 secured to the shaft 40. The formation 78 is held in the recess 56 by a collar 89 surrounding the spindle 72 and secured to the ring 55. The spindle 72 and the shaft 40 rotate together in the operation of the apparatus. The uppermost position of the agitator member 38 is determined by engagement between the collar 80 and the lower end of the shaft 22.

The upper end portion of the spindle 72 has a coarse screw thread 82 formed thereon (FIGURE 2) the length of the thread being somewhat greater than the maximum required amount of adjusting movement of the agitator member 38. This thread 82 is screwed into a co-operating Phosphor bronze captive nut 84 which is prevented from disengaging the spindle '72 by a nut 85 and lock-nut 86 screwed on to the spindle 72 above the nut 84; engagement between the nut 85 and the captive nut 84- deter mines the lowermost position of the agitator member 38. Rotation of the spindle 72 relative to the nut 84 causes vertical movement of the member 38.

The upper portion of the shaft 22 (FIGURE 2) passes loosely through a hole 88 in a fiat plate 90, which is secured to the gear box casing. Immediately above the plate 90 a collar 92 is attached to the shaft 22 by a set screw 94, and above the collar 92, a brake drum 96 is -mounted freely on the shaft 22.

The brake drum 96 comprises a channel-sectioned annulus 98 in the inner periphery of which is secured a bearing bush 160 which rotatably engages the shaft 22, for rotation thereabout. The webs of the channel cross-section are directed upwards, and the outer periphery of the drum 96 provides an outer cylindrical braking surface 192.

The means for moving the agitator member 38 up and down also comprises a differential gear mechanism associated with the spindle 72 and the captive nut 84; this mechanism comprises an annular bevel gear crown wheel 104 secured in the base of the drum 96 and freely rotatable about the shaft 22, the gear teeth of the wheel 104 being directed outwards at an angle of 45. Keyed to the shaft 22 immediately above the crown wheel 104 is a collar 106, a key (not shown) extending between a keyway (not-shown) in the collar 106 and a slot 198 in the .shaft .22. The collar 106 ,provides two diametricallyopposed coaxial radial bosses 110 and in each boss 119 is mounted a radial spindle 112 upon which is mounted freely for rotation a bevel spurred pinion 114; the pinions 114 are in mesh with the crown wheel 1194.

Above the brake drum 96 is located a further brake drum 116 in the inner periphery of which is located a bearing bush 118 which engages the shaft 22 for rotation thereabout. The drum 116 corresponds generally in construction and arrangement with the drum 96 and is described in so far as it differs therefrom. The webs of the channel cross section of the drum 116 are directed downwardly. An annular crown wheel 12% secured in the drum 116 coaxially with the crown wheel 164 is freely rotatable about the shaft 22 and is in mesh with the pinions 114.

There is a slight axial separation between an upper rim 122 of the drum 96 and a lower rim 124 of the drum 116. The rim 122 has a plurality of small recesses 126 (only two of which are shown) extending around its inner periphery uniformly spaced from each other; similarl the rim 124 has a pluralityiof small recesses 128 extending around its inner periphery uniformly spaced from each other. A spring loaded plunger 139 extends outwardly from each spindle 112 and each plunger 131 is adapted to engage :a pair of

opposite recesses

126, 128. Engagement between the plungers and the recesses 126, 123 restrains relative rotational movement between the drums 96, 116 in the absence of substantial force urging such movement and permits it when one or other of the drums 96, 116, is stopped.

The upper brake drum 116 is held in position on the shaft 22 by a keeper plate 132 secured to the upper end portion of the shaft 22. The captive nut 84 has a small diameter spigot portion 134 at its upper end and this is keyed by a key 135 into a passage 136 in an end cap 138 which is secured to the upper surface of the upper brake drum 116.

The apparatus comprises brake mechanism (FIGURES 2 and 4) adapted so to act upon the drums 96, 116 that the spindle 72 moves up or down as required. The brake mechanism comprises two brakes, one associated with each drum 96, 116, and means so associating the brakes that the mechanism is movable from a neutral condition, in which neither brake engages its drum to a first operative condition in which only one brake engages its drum, and from the neutral condition to a second operative condition in which only the other brake engages its drum. Each brake comprises two opposite arcuate brake shoes 142 each comprising a brake lining 144; each shoe 142 being pivoted at one end in one or other of two hingepins 146 secured in the plate 99 to one side of the drums 96, 116. The brakes and the drums 96, 116 are enclosed -in a casing 147 which is secured to the plate 911. At the side of the drums 96, 116 remote from the pins 146 one shoe 142 of the upper brake is connected by a link 148 and a lever 149 to a vertical spindle 150; the link 148 is pivotally connected to one end portion of the lever 149 and also is pivotally connected to the shoe 142; the lever 149 is secured to the vertical spindle 150 which is mounted in the plate 911 for rotational movement about its axis; similarly the other shoe 142 of the upper brake is connected by a link to the other end portion of the lever 149. Similarly the shoes 142 of the lower brake are connected by links 151 to the end portions of a lever 153 also secured to the spindle 150. The spindle is a close fit in a ring 152 secured to the upper surface of the plate 91) and also in a ring 154 secured to the lower surface of an upper wall 156 of the casing 147; the spindle 150 extends upwardly through the casing 147 and has a handle 140 secured to its upper end portion. When the handle 140 is moved in a clockwise direction from a neutral position (FIGURE 4) the lower drum 96 is engaged by its brake shoes 142 and when it is moved in an anticlockwise direction from the neutral position the upper drum 116 is engaged by its brake shoes 142.

The apparatus comprises means for locking the brake mechanism in its neutral condition. A horizontal tube 158 is secured in a vertical wall 160 of the casing 147 and a locking pin 162 is mounted for sliding movement in the tube 158. A horizontal'bore 164 extending through the ring 152 is aligned with the tube 158. A spring 166 acts between a cap 168 secured to an outer end portion of the tube 158 and a collar 170 secured to the pin 162, to urge the pin 162 to the left (FIGURE 2). The pin 162 extends outwardly through the cap 168 and its outer end portion has a handle 171, secured thereto. A horizontal bore 172 extends through the spindle 150 and in the neutral position of the handle 140 the bore 172 is aligned with the bore 164 and the tube 158. The handle 140 is locked in this position by the pin 162 extending through the

bores

164, 172. When it is required to move the handle 141) from its neutral position the handle 171 is pulled against the action of the spring 166 to move the the bore 172 is now no longer in alignment with the bore 164. On return of the handle 140 to its neutral position the spring 166 urges the pin 162 into the bore 172 again to relock the handle 140 in said position.

The apparatus comprises a further casing 174 secured on top of the casing 147. The spindle 72 extends into the casing 174 and its upper end portion has a horizontal pointer 176 secured thereto. The pointer 176 extends outwardly of the casing 174 through a slot 178 therein and is arranged to move up and down a slot 179 in a scale member 130 which is'secured to the casing 174. The scale member 180 is graduated (not shown) and the position of the pointer 176 on the scale member 180 indicates the position of the agitator member 38.

pin 162 out of the bore 170, and the handle 140 is moved;

In the operation of the apparatus rotation of the shaft 22 causes the

tubes

26, 34 to rotate; rotation of the

tubes

26, 34 causes the shaft 40 and agitator member 38 to rotate; rotation of the shaft 40 causes the spindle 72 to rotate. Rotation of the shaft 22 also causes rotation of the pinions 114 with the shaft 22 about the axis of the shaft 22 when the handle 140 is in its neutral position; this rotation of the pinions 114 causes rotation of the brake drums 96, 116, the spring loaded plungers 130 restraining the drums 96, 116 against rotation relative to each other; the captive nut 84 rotates with the drum 116 and thus there is no relative rotation between the nut 64 and the spindle 72 and the agitator member 38 does not move axially.

When it is required to move the agitator member 38 upwardly the handle 14%) is moved in an anticlockwise direction to apply the upper brake shoes 142 to the upper drum 116 to stop the rotation of the drum 116; the spring loaded plungers 130 now permitting rotation of the drum 96 relative to the drum 116. The spindle 72 is now rotating relative to the captive nut 84 and the spindle 72 moves upwardly; this causes upward movement of the shaft and the agitator member 38. When the required position of the agitator member 38 is reached as shown by the position of the pointer 176 the handle 140 is moved back to its neutral position.

When it is required to move the agitator member 38 downwardly the handle 140 is moved in a clockwise direction to apply the lower brake shoes 142 to the lower drum 26 to halt the rotation of the drum 96. This causes the speed of the drum 116 to double, through the crown Wheels 104, 120 and the pinions 114; the captive nut 84 is now rotating faster than the spindle 72 and this causes downward movement of the spindle 72, the shaft 40 and the agitator member 38. When the required position of the agitator member 38 is reached the handle 140 is returned to its neutral position.

I claim:

1. Apparatus for aerating liquids in a container comprising an aerator member disposed to extend into said liquid, a rotatably mounted vertical shaft assembly comprising a plurality of longitudinally slidably, non-rotatably connected shaft sections, means mounting said aerator member for rotation with the lowermost of said shaft sections, means for rotating said shaft assembly, and means for effecting relative sliding movement of said shaft sections during rotation of said assembly for maintaining a desired operating level of said aerator member with respect to said liquid.

2. Apparatus for aerating liquids in a container comprising an aerator member disposed to extend into said liquid, a rotatably mounted vertical shaft assembly comprising two longitudinally slidably non-rotatably connected telescoped upper and lower shaft sections, means mounting said aerator member on said lower shaft section, means operably connected to said upper shaft section for rotating said shaft assembly and means for effecting relative sliding movement of said shaft sections for varying the operating level of said aerator member with respect to said liquid.

3. In the apparatus defined in claim 2, a longitudinally flexible sleeve connecting the lower end of said upper shaft with said aerator member for protectively enclosing the lower end of said lower shaft section.

4. Apparatus for aerating liquids in a container comprising an aerator member disposed to extend into said liquid, a rotatably mounted vertical shaft assembly comprising a pair of longitudinally slidabiy non-rotatably connected shaft sections, one of said shaft sections being hollow and the other shaft section being telescoped therein and projecting from the lower end thereof, a drive motor operably connected to said one shaft section for rotating said shaft assembly, means mounting said aerator member on said other shaft section, and means for effecting relative sliding movement of said shaft sections for varying the operating level of said aerator member with respect to said liquid comprising mechanism interposed between said shaft sections and selectively operable to maintain said shaft sections against relative movement or to controllably raise or lower said other shaft section, saidmechanism being operatively connected to be actuated by said rotating one shaft section.

5. In the apparatus defined in claim 4, said mechanism comprising a coupling threaded on said other shaft section and operably connected through reversing means to said one shaft section.

6. Liquid aeration apparatus comprising (a) a shaft, (b) means for rotating the shaft about its axis, (c) an aerator member mounted on the shaft for rotation therewith about said axis, (d) a differential gear mechanism comprising a first set of two coaxial gear wheels one on either side of the axis of the shaft, said wheels being freely rotatable about an axis at right angles to the axis of the shaft and also being mounted for rotation with the shaft about its axis, and a second set of two coaxial gear wheels restraining relative rotational movement between the gear wheels of the second set in the absence of substantial force urging such movement and permitting such movement when one or the other of said wheels is stopped, and (h) brake means for stopping rotation of one or the other of the gear wheels of the second set to cause axial movement of the second screw threaded member I to move the aerator member axially in a required direction.

7. Liquid aeration apparatus comprising (a) a drive shaft, (b) means for rotating the drive shaft about its axis, (c) a second shaft mounted for coaxial rotation with the drive shaft and for axial movement relative to the drive shaft, (d) an aerator member mounted on the second shaft for rotation therewith, (e) a differential gear mechanism comprising a first set of two coaxial gear wheels are on either side of the axis of the drive shaft, said wheels being freely rotatable about an axis at right angles to the axis of said shaft and also being mounted for rotation with said shaft about its axis, and a second set of two coaxial gear wheels in mesh with the first set of gear wheels and freely rotatable about the axis of said shaft, (f) a first screw threaded member coaxial with the wheels of the second set and mounted for rotation with one wheel of said second set, (g) a second screw threaded member in screwed engagement with the first screw threaded member, and connected directly to the second shaft, (h) means for restraining relative rotational movement between the gear wheels of the second set in the absence of substantial force urging such movement and permitting such movement when one or the other of said wheels is stopped, and (i) brake means for stopping rotation of one or the other of the gear wheels of the second set tocause axial movement of the second screw threaded member to move the aerator member axially in a required direction.

8. Liquid aeration apparatus comprising (a) a shaft, (b) means for rotating the shaft about its axis, (c) an aerator member mounted on the shaft for rotation therewith about said axis, (d) a differential gear mechanism comprising a first set of two coaxial gear wheels one on either side of the axis of the shaft, said wheels being freely rotatable about an axis at right angles to the axis of the shaft and also being mounted for rotation with the shaft about its axis, and a second set of two coaxial gear wheels in mesh with the first set of gear wheels and freely rotatable about the axis of the shaft, (e) two brake drums, one surrounding and secured to each gear wheel of the second set, (f) a first screw threaded member coaxial with the wheels of the second set and mounted for rotation with one wheel of said second set, (g) a second screw threaded member in screwed engagement with the first screw threaded member, mounted for rotation with the shaft and for axial movement with the aerator member, (h) means for restraining relative rotational movement between the brake drums in the absence of substantial force urging such movement and permitting such movement when one or the other of said drums is stopped, and (i) brake mechanism comprising two brakes, one associated with each drum and each adapted to engage its drum to stop rotation of the drum to cause axial move ment of the second screw threaded member to move the aerator member axially in a required direction.

9. Liquid aeration apparatus comprising (a) avshaft, (b) means for rotating the shaft about its axis, (c) an :aerator member mounted on the shaft for rotation therewith about said axis, (d) a differential gear mechanism "comprising a first set of two coaxial gear wheels one on either side of the axis of the shaft, said wheels being freely rotatable about an axis at right angles to the axis of the shaft and also being mounted for rotation with the shaft about its axis, and a second set of two coaxial gear wheels in mesh with the first set of gear wheels and freely rotatable about the axis of the shaft, (e) two brake drums, one surrounding and secured to each gear wheel of the second set, (f) a first screw threaded member coaxial with the wheels of the second set and mounted for rotation with one wheel of said second set, (g) a second screw threaded member in screwed engagement with the first screw threaded member, mounted for rotation with the shaft and for axial movement with the aerator member, (h) means for restraining relative rotational move,- ment between the brake drums in the absence of substantial force urging such movement and permitting such movement when one or the other of said drums is stopped, and (i) brake mechanism comprising two brakes, one associated with each drum and each comprising two opposite brake shoes adapted to engage its drum to stop 8 rotation of the drum to cause axial movement of the second screw threaded member to move the aerator member axially in a required direction.

10. Liquid aeration apparatus comprising (a) a shaft, (b) means for rotating the shaft about its axis, (c) an aerator member mounted on the shaft for rotation therewith about said axis, (d) a differential gear mechanism comprisinga first set of two coaxial gear wheels one on either side of the axis of the shaft, said wheels being freely rotatable about an axis at right angles to the axis of the shaft and also being mounted for rotation with the shaft about its axis, and a second set of two coaxial gear wheels in mesh with the first set of gear wheels and freely rotatable about the axis of the shaft, (e) a first screw threaded member coaxial with the wheels of the second set and mounted for rotation with one wheel of said second set, (f) a second screw threaded member, in screwed engagement with the first screw threaded member, mounted. for rotation with the shaft and for axial movement with the aerator member, (g) means for restraining relative rotational movement between the gear wheels of the second set in the absence of substantial force urging such movement and permitting such movement when one or the other of said wheels is stopped, (h) brake means for stopping rotation of one or the other of the gear wheels of the second set to cause axial movement of the second screw threaded member to move the aerator member axially in a required direction, and (i) means for locking the brake means in a neutral condition in which neither of said gear wheels is stopped.

11. Liquid aeration apparatus which comprises (a) a liquid container, (b) a vertical shaft disposed centrally of the container, (0) an aerator member secured on the shaft for rotation therewith in the container, said aerator member comprising an inverted symmetrical frusto-conical shell coaxial with the shaft, a circular cylindrical projection extending downwardly from the shell coaxially therewith, and a plurality of vertical planar arms extending from the periphery of the projection tangentially of the projection along the lower surface of the shell, (d) a motor, (e) a gear box, the input side ofwhich is connected to the motor and the output side of which is connected to the shaft to rotate it, (f) a'diiferential gear mechanism which comprises a first set of two coaxial gear wheels one on either side of the axis of the shaft, being freely rotatable about a horizontal axis, and also being mounted for rotation with the shaft about the axis of the shaft, and a second set of two coaxial gear wheels in mesh with the first set of gear wheels and freely rotatable about the axis of the shaft, (g) a nut coaxial with, and mounted for rotation with, one wheel of the second set, (h) a threaded spindle screwed into the nut, mounted for rotation with the shaft, and for up and down movement with the aerator member, (i) means for restraining relative rotational movement between the gear wheels of the second set in the absence of substantial force urging such movement and permitting such movement when one or the other of said wheels is stopped, and (j) brake means for stopping rotation of one or the other of the gear wheels of the second set to cause axial movement of the threaded spindle to move the aerator member axially in a required direction.

References Cited by the Examiner UNITED STATES PATENTS 584,627 6/1897 Deeble 259-108 2,195,234 3/1940 Brown 259-122 X 2,262,412 11/1941 Weinig 259108 FOREIGN PATENTS 499,111 11/1950 Belgium. 919,467 2/1963 Great Britain.

CHARLES A. WILLMUTH, Primary Examiner.