The present invention relates to a device for cleaning the interior of a container, for example, a tank which can hold liquid or semi-liquid foods during storage and transportation.

When containers hold food products, the interior must be thoroughly cleaned prior to refilling to avoid bacterial growth which may result from any residue.

At present, cleaning devices are utilised which deliver a cleaning fluid to the interior walls of the container. The jet or spray of cleaning fluid must be well-defined to ensure that the entire interior surface is cleaned. Typically, the cleaning fluid will be hot and possibly caustic and, therefore, a reliable cleaning device must operate in a hot and possibly hostile environment.

In all types of cleaning device, in particular, in the field of tank cleaning, an important consideration is the speed of cleaning. Clearly, if the cleaning device operates swiftly, a larger number of containers can be cleaned and subsequently refilled in a given time.

It is also important that the cleaning device be economical in the use of cleaning fluid. In general, this means that the bore or bores through which the cleaning fluid exits the cleaning device should be kept as small as possible to limit the flow while maintaining the fluid coverage and providing adequate

cleaning power.

An important feature of jet tankwashers is that the jets of cleaning fluid strike the surface in a steady stream so that the maximum momentum can be imparted to the surface to ensure complete removal of any residue. Also, it is essential that the jet be directed so as to play on all the internal surface of the tank.

It is also important that the tankwasher be reliable and practically maintenance free.

The present invention provides a device for cleaning the interior of a container comprising a device for cleaning the interior of a container comprising a body rotatably mounted to the interior of the container, the body having a bore therethrough for the passage of cleaning fluid, at least one nozzle rotatably mounted on the body, the or each nozzle having a bore therethrough for the passage of cleaning fluid, means for imparting rotation to the or each nozzle about two axes and damping means associated with the or each nozzle to control the period of rotation.

Preferably, the means for imparting rotation comprises providing the bore --through the or each nozzle with a curvature such that rotation is imparted as a reaction to the flow of fluid therethrough.

Preferably, the damping means comprises a hydraulic piston.

In one embodiment, the device comprises two

nozzles and a means to vary the speed of rotation of the nozzles within each period of rotation.

Preferably, the means to vary the speed of rotation comprises a bearing which is eccentric with respect to one axis and to which the piston is connected.

In one aspect of the invention the two axes of rotation are mutually perpendicular.

Advantageously, the bore through the body has no constrictions therein.

Conveniently, means is provided to straighten the flow of fluid in the bores in the or each nozzle.

Preferably, the or each nozzle is rotatably mounted on the body by means of pair of bearings on which the hydraulic thrust caused by fluid flow through the device is balanced.

In a further aspect of the invention the device comprises means to alter continuously the path traced on the interior of the container by the fluid emerging from the or each nozzle upon each rotation about one axis.

Preferably, the means to alter the path comprises first and second co-operating gears wherein the number of teeth on the first gear is different from the number of teeth on the second gear.

The invention will now be described in detail, by way of example only, with reference to the accompanying

drawings in which:

Figure 1 is a side elevation of a device in accordance with the present invention;

Figure 2 is a sectional view of the device of Figure 1 taken along the line A-A;

Figure 3 is a schematic diagram illustrating the path traced by a jet of cleaning fluid emerging from the device;

Figure 4 is a schematic diagram indicating which areas of a tank receive maximum coverage of cleaning fluid; and

Figure 5 is a diagram similar to Figure 4 showing the effect of mounting the tankwasher horizontally in the tank.

Referring to Figures 1 and 2, the cleaning device 10 comprises a main body 11 rotatably mounted to an inlet tube 12 which is rigidly secured to the container.

The body 11 has a first hole 13 through the top, a second hole 14 at the left-hand side, a third hole 15 at the right; the base 16 is closed off. The second hole 14 is sealed and the first and third holes 13 and 15 are connected so that the body 11 is substantially hollow and defines a continuous bore therethrough for the passage of cleaning fluid. The bore is arranged such that it presents no constrictions to the fluid flow. The reasons for this are discussed later. The first, second and third

holes 13-15 are threaded and the various other parts of the device 10 are screwed into these holes.

Screwed into the first hole 13 at the top of the body as seen in Figure 2 is a track 17. This track 17 is formed with upper and lower curved surfaces each forming a bearing race in which run a number of balls. The lower bearing 18 absorbs the hydraulic thrust of the pressure of cleaning fluid in the hollow body 11. The pressure of the liquid forces the balls of the lower bearing 18 and the inlet tube 12 into the track 17 and supports the rotation of the body 11 about the vertical axis Y. The upper bearing 19 locates the body 11 as a journal bearing allowing it to rotate correctly about this vertical axis Y.

The inlet tube 12 is machined as a solid part with a bevel gear 20 at the bottom end. It has curved tracks to form the matching races for the upper and lower bearings 18,19. The track 17 is machined in two halves. These when put together with the two rings of balls embrace the inlet tube 12 and provide solid support for the rotation of the body 11 and the parts attached to it.

The body 11 as a whole rotates about the vertical axis Y as shown in Figure 2. A seal 21 bearing on the inlet tube 12 is constructed from a coiled ring of plastic material, typically 25% carbon filled teflon, though other materials could be used. This ring of plastic is blown onto the circumference of the inlet tube 12 and against the inside edge of the track 17 sealing the device 10 and preventing the escape of cleaning fluid to the outside.

Mounted in a horizontal position in body 11 as seen in Figure 2 is the nozzle tube 22. The nozzle tube 22 defines a bore 23 which passes the cleaning fluid on its way to the nozzles 35. This nozzle tube 22 is supported at the right hand end by a ball bearing 24 mounted in the curved surfaces of another track 25. This second track 25 is again constructed in two halves to allow it to clamp around the nozzle tube 22. A similar ball bearing 26 supports the nozzle tube 22 at the left-hand end mounted in a third track 27. This is not split. All the tracks described so far are screwed into the holes in the body 11.

Two seals 28,29 are fitted on the nozzle tube 22. One seal 28 is located at the right-hand end in the second track 25 and the second seal 29 is located at the left-hand end in the third track 27. The effect of the two seals 28,29, which are of the same diameter, is that there is no net hydraulic thrust due to the internal pressure of cleaning fluid on the nozzle tube 22. It can rotate freely without the need to absorb the end thrust from either direction since the hydraulic forces are balanced out The two ball bearings 24,26 do not have hydraulic forces imposed on them and can better absorb other forces due to the piston action which will be described later.

As mentioned above, machined at the bottom of the inlet tube 12 is a bevel gear 20. This meshes with a similar bevel gear 30 mounted on the end of the nozzle tube 22. This bevel gear 30 is located by a key 31 to the nozzle tube 22, positioned by a spacer 32 and locked into place by a bolt 33.

Mounted on the right hand end of the nozzle tube

22 are two curved tubes 34 leading to two nozzles 35.

Two nozzles are shown, but more, three, four, six or more may be employed to give a sufficiently dense coverage.

Fitted in the curved tubes 34, before the nozzles 35 are crossed metal strips 36, which act as flow straighteners to remove the swirl from the water before it reaches the nozzles 35. The water reaching these nozzles 35 is accelerated through the tapered section and formed into a rod like jet of liquid as it emerges from a hole 37 in the end of the nozzle 35. These holes 37 can be of different sizes to suit the requirements of the pump feeding the tankwasher and the power of the jet required for cleaning the tank. The sizes may typically be 5mm or 6mm but other sizes are possible.

In use, cleaning fluid is fed into the an inlet tube 22 and through into the main body 11. From there it flows through the nozzle tube 22 and the curved tubes 34 to emerge from the two nozzles 35. This flow is represented by the letters, A, B, C and D in Figure 2 which track its progress through the device 10. The emerging cleaning fluid is in jet form and these jets travel outwardly and impinge on the walls of the tank being cleaned.

For effective cleaning it is desirable for the nozzles to produce stable jets of fluid, i.e jets which do not break up into a spray, at a high velocity. This is because strong jets which strike the interior surfaces of the container in a steady stream impart maximum momentum to ensure complete

removal of any residue. Using high velocity jets also ensures swifter cleaning. The fact that the bore through the main body 11 has no constrictions avoids accelerating the fluid flow and thereby creating turbulence which would reduce the maximum jet velocity possible. Similarly, the use of flow straighteners 36 also removes turbulence and increases the stability of the jets.

The acceleration of the cleaning fluid through the nozzles 35 create a reaction effect and a torque acting on the axis X of the nozzle tube 22. This reaction torque is the motivating power to rotate the device 10.

As the nozzle tube 22 rotates about the horizontal axis X, impelled by the reaction forces of the fluid flowing through the nozzles 35, it causes the meshed teeth of the bevel gears 20,30 to rotate the body 11 about the vertical axis Y. This rotation about two axes causes the emerging jets of cleaning fluid to trace a pattern over the internal surfaces of the tank being cleaned similar to the skeins of a ball of wool as illustrated in Figure 3. It is important that this pattern is repeated as little as possible to ensure a thorough coverage of the tank walls and an effective clean.

Therefore, the two bevel gears 20,30 will preferably have a different number of teeth. The first bevel gear 20 might have typically 39 teeth and the second bevel gear 30 might have 40 teeth. The effect of this is to step the jet pattern by the pitch of one tooth each revolution. The jet will then traverse a differing path each turn and give a more

dense coverage of the tank surface.

Unless restrained the jet rotation would wind away at high speed. However, the slower the jet moves, the better their rod-like form and the harder the cleaning impact. Thus, it is necessary to control this rotation to a required rate. The braking of this rotation, to control the speed to a rate slow enough to prevent jet break up, is the purpose of the mechanism described below.

In the centre of the nozzle tube 22 is machined a bearing journal 38 which is eccentric with respect to the horizontal axis X of the nozzle tube 22. The eccentric journal 38 is linked to a connecting rod 39, the bearing being formed by 15 rollers 40 enclosed between the surface of this journal bearing 38 and the large end diameter of the connecting rod 39.

The effect of the rotation of the nozzle tube 22 is to cause the connecting rod 39 to rise and fall in a vertical direction as viewed on Figure 2. Connected to the end of this connecting rod 39 is a piston 41. The piston 41 has a pin 42 through it and a bush 43 to prevent metal to metal contact. This bush 43 might be of a plastic material again typically 25% carbon filled teflon.

The piston 41 has wrapped around it a tape 44 of a suitable bearing material. A typical material is

25% carbon filled teflon which again prevents metal to metal contact between the piston 41 and the wall 45 of the cylindrical lower part of the body 11, which defines two chambers 46,48 separated by the piston. The two chambers 46,48 are filled with cleaning fluid

- lo ¬

in use .

As the piston 41 rises and falls cleaning fluid is continuously displaced from one chamber 46 to the other chamber 48 and vice versa. It is the viscous drag exerted by the cleaning fluid on the piston 41 which provides the damping action which controls the speed of rotation of the device 10. In one embodiment there is no venting of the chamber 46 below the piston 41 and so the cleaning fluid can only escape through the clearance at the side of the piston 41. Alternatively it is possible to drill a calibrated hole 47 in the piston 41 and this is shown in Figure 2.

The total effect of the device 10 in operation can now be seen. The reactions of the jets of cleaning fluid accelerating through the nozzles 35 cause the whole assembly to rotate about the vertical axis Y and the nozzles 35 to rotate at the same time, about the horizontal axis X as seen in Figure 2. This rotation is controlled by the work being done by the piston 41 pumping cleaning fluid within the chambers 46,48 at the lower end of body 11.

A further feature of the device 10, to reduce the inherent limitations of the geometry of rotation is described below.

Any tankwasher device that rotates about a central vertical axis will traverse a jet through the top and bottom axis of rotation. If the path traced by these jets is seen as lines on a globe, then each jet will traverse lines of longitude at constant speed and will go through the north and south poles of that

globe as seen in Figure 3.

This jet pattern will be a disadvantage for instance if the tankwasher is fitted in a long horizontal tank. This is shown in Figure 4. The maximum jet coverage is up and down as indicated by arrows A, with little jet coverage directed towards the ends of the tank as indicated by arrow B.

One way to overcome this problem would be to lay the device on its side, so that the centre line axis Y-Y is laid along the horizontal axis of the tank, as shown in Figure 5 so that more jets are directed towards the ends of the tank as shown by arrows A, and fewer up and down as indicated by arrows B.

However, this is not generally possible due to the limited access to a tank and the difficulty of moving such a horizontally mounted tankwasher into place.

It is a feature of the present invention that, in the two nozzle version, this effect is much reduced by varying the speed of rotation of the nozzle tube 22 within each period of rotation.

The nozzle tube 22 rotates and drives the connecting rod 39 and thus the piston 41. As the eccentric journal 38 of the nozzle tube 22 goes through top and bottom dead centre, the resisting torque of the piston 41 pumping against the cleaning fluid in the chamber 46 is reduced. The rotation speeds up for a small section of the rotational arc, until the piston 41 takes up the hydraulic load again. The nozzles in effect 'flick' through top and bottom

dead centres, moving quickly through the north and south poles.

The overall effect is that the jets emerging from the nozzles 35 dwell longer on the long horizontal axis of the tank and move quickly through the poles. Thus, better coverage of the jets over the entire internal surface of the tank is obtained.