Background of the invention

The invention relates to a method for the cleaning of the inside surfaces of a tank or similiar spaces by means of a jet of fluid from a nozzle inside the tank, said nozzle being capable of being both rotated around an axis and swung, oscillated, around an axis at right-angles hereto in a predetermined manner, so that the jet of fluid is tra¬ versed around at the same time as it is moved up and down inside the tank, and also an apparatus for the execution of the method.

The interior of the tank, such as an oil storage tank on a ship, containers, vessels and the like, must at intervals be cleaned of sludge and other impurities which are depo¬ sited on the inside surfaces of the tank.

This is usually carried out by means of a cleaning appara¬ tus which can be mounted permanently on the tank, and which is provided with a nozzle mounted on the end of a shaft which extends a suitable distance down into the tank.

The nozzle is supplied with cleaning fluid under pressure which is discharged while the nozzle is brought to move in a predetermined pattern, so that the cleaning fluid sy¬ stematically hits and sweeps all surfaces and hereby dis- solves and flushes away the sludge deposits which hereafter can be led out together with the fluid.

By means of a drive unit in the apparatus, the nozzle can both be turned around in relation to the shaft in a hori- zontal plane and swung up and down in a vertical plane. It is hereby ensured that the cleaning pattern is one which

ensures an effective sweeping of all surfaces.

Such a cleaning apparatus is known from the description in GB 2,028,113. The apparatus is provided with a rotatable guide having a spirally-extending channel on the outer side in which a pin can run and be moved in the vertical plane during the turning of the guide. The pin is connected to a stay which is hereby moved upwards and downwards. By let¬ ting the nozzle be in rack-and-pinion engagement with this stay, the nozzle can be swung up and down at the same time that the guide and herewith the nozzle is rotated.

The channel can have various rakes for the generation of a different degree of swinging movement, so that there arises a predetermined degree of nozzle swing suited for the in¬ terior of the tank. The nozzle and herewith the cleaning jet can thus sweep preselected places more intensively, namely such places which experience has shown require more cleaning than others.

This apparatus is of very complicated construction, and there is no possibility of being able to change the move¬ ment pattern for the swinging of the nozzle which is de¬ termined by the configuration of the channel. The nozzle movement and herewith the cleaning pattern cannot be alter¬ ed, which means that further cleaning time and cleaning fluid must be used in the cases where the cleaning is not adequate and must therefore be repeated until all deposits have been removed. In practise, this will typically be in the corners in the bottom of the tank.

Advantages of the invention

According to the invention, by using a method whereby the swinging movement of the nozzle is predetermined so that it is turned at those areas of the tank which require the most

cleaning, it is ensured that the greater cleaning effect resulting from the turning time is utilized in the best possible manner. The cleaning apparatus is hereby utilized in the best possible manner, in that optimum use can be made of the cleaning time and, furthermore, a saving is achieved in both energy and cleaning fluid.

In the event of a tank being extremely dirty, the apparatus can be set to provide a tightly-meshed pattern of movement for the nozzle, which ensures the most effective cleaning in the shortest possible cleaning time, hereby saving fluid, time and energy.

By using a method according to claim 2 whereby the oscil- lating swinging speed of the nozzle can be steplessly varied during operation, a far more effective cleaning can be achieved in that the adjacency of the jet's track, and herewith the intensity of same, can be adjusted to suit re¬ quirements. This will save time, cleaning fluid and energy, in that the distance between the jets during rotation in¬ side the tank can be adjusted to provide a perfect cleaning result.

According to claim 3, the ability to adjust the speed at which the nozzle is oscillated ensures that an optimum de¬ gree of efficiency is achieved, in that cleaning can be effected with from very great to less adjacency, thus ad¬ justing the intensity with which the cleaning jet sweeps the inside of the tank.

As disclosed in claim 4, by allowing the angle at which the nozzle oscillates to be greater than 180°, the nozzle will be able to swing between an upper vertical position, in which the nozzle points upwards, and a lower inclined posi- tion in which the nozzle points at an angle downwards, pointing towards the furthermost area of the bottom which

experience has shown is the dirtiest, this area thus being effectively cleaned at the turning point of the nozzle.

According to claim 5, by using an apparatus comprising a turbine-driven worm drive which drives a worm wheel and, via a connecting link a pinion which is engaged with a rack, which in turn is in toothed engagement with the nozzle, an operationally simple construction and at the same time an effective oscillation of the nozzle is achieved.

As disclosed in claim 6, by allowing the radius of the worm wheel to be less than that of the gear wheel, a rack move¬ ment is achieved which provides the nozzle with an angle of oscillation of more than 180° in the vertical plane.

As disclosed in claim 7, by giving the worm wheel a vari¬ able degree of turn, the desired possibility of stepless adjustment of the speed of movement is achieved, and here- with of the speed at which the nozzle oscillates.

Finally, as disclosed in claim 8, it is expedient to con¬ figure the adjustment as a limitation of the stroke length of the drive unit by means of a manually-rotatable eccent- ric disk, whereby a simple and reliable means of adjustment is achieved.

The drawing

In the following section, an example embodiment of the in¬ vention will be described in more deatil with reference to the drawing, where

fig. 1 shows an example of the mounting of the apparatus on the top of a tank,

fig. 2 shows the apparatus itself,

fig. 3 shows the drive unit itself,

fig. 4 shows a geometric illustration of a cycle in the degree of nozzle oscillation,

fig. 5 shows a graph which depicts the angular position of the nozzle in relation to time, and

fig. 6 shows an example of a pattern of movement follow¬ ed by a cleaning nozzle at the bottom of a tank.

Description of the example embodiment

In fig. 1 is shown an example of the mounting of a cleaning apparatus 5 on the top of separate tanks 1 or sections of the tank. The tank itself comprises the sides 2, the bottom 3 and the top on which the apparatus 5 is mounted at a place 4 expedient for the cleaning.

Each apparatus 5 is provided with a nozzle 12 which can be traversed around in the tank while at the same time it swings upwards and downwards, as will be described later.

An embodiment of the actual cleaning apparatus 5 is shown in fig. 2.

This comprises a drive unit for the nozzle, said drive unit being outside the tank and built into a housing 6 with a cover 7 and a flange connection 9 for cleaning fluid 13, a turbine housing 8 and a mounting flange 10 for abutment against the top of the tank.

Extending inside the tank 1 there is a pipe 11 on the end of which the nozzle 12 is mounted in such a manner that it

can be turned around in the horizontal plane while at the same time it can be swung upwards and downwards oscillating in an arc 41, as indicated in fig. 2.

The mechanism for turning the nozzle 12 and for the regula¬ tion of the nozzle's pattern of movement inside the tank 1 will be described with reference to fig. 3, where the hous¬ ing 6, the cover 7, the flanges 9 and 10 as well as the turbine housing 8 and the pipe 11 are indicated with stippled lines.

In the turbine housing 8 there is a turbine rotor 14 su¬ spended in the flow of fluid 13 which is led from here down through the outer pipe 11 to the nozzle at the end of the outer pipe 11.

The turbine rotor 14 drives a shaft 15 to which there is connected a crankwheel 16 with a crank 17. On this crank 17, suspended in a sliding manner, there is a pushrod 18 which at its opposite end is connected to a rocker arm 19. The end of this rocker arm 19 is provided with a one-way clutch 20 of commonly-known type for the transfer of the rocking movement to a turning movement on a worm shaft which is hereby turned in only one direction.

The worm 21 on the shaft is in engagement with a worm wheel 22 which is turned as a result of the drive mechanism.

To the worm wheel 22 there is secured a downwardly-extend- ing main shaft 23. The nozzle 12 is mounted on the end of said shaft 23 in such a manner that the turning movement of the worm wheel 22 is transferred to the nozzle 12, which is hereby rotated in the horizontal plane inside the tank, as indicated in fig. 2.

The speed of the turning movement depends solely on the

speed of rotation of the turbine rotor 14 and the gearing exchange effected by the drive unit.

The turning speed can therefore only be regulated by means of a not-shown arrangement for the regulation of the flow of fluid 13 through the turbine housing 8, or by changing the stroke length of the crank 16, 17.

In addition to this turning of the nozzle 12, the nozzle 12 is swivelled upwards and downwards in an oscillating move¬ ment 41, as indicated in fig. 2.

This movement is brought about by a drive head 24 with an inclined slide surface which lies up against a carrier arm 25. This arm 25 is provided with a dog 27 which, assisted by a spring 28, lies up against an eccentric cam 29.

To the eccentric cam 29 there is fastened an adjustment wheel 30 so that the clearance of the carrier arm 25 in relation to the drive head 24 can be adjusted in a stepless manner. The turning movement of a worm shaft 31 which, via a one-way clutch 26 is mounted on the arm 25, 27, can here¬ by be steplessly varied.

The worm shaft 31 is in engagement with a worm wheel 32 which is mounted on a shaft 33. In the worm wheel 32 there is provided a stud 34 on which there is mounted a connect¬ ing link 35. At its opposite end, the link is connected to a stud 36 on a pinion 38 which is mounted on an axle 37.

When the worm wheel 32 is turned, the pinion 38 is moved forwards and backwards on the axle 37.

The pinion 38 is in toothed engagement with a rack 39 which extends tangentially to the pinion, and which is hereby moved upwards and downwards while at the same time being

rotated by the worm wheel 22. At the opposite end of the main shaft 23 there is mounted a rack 43 which is in en¬ gagement with a pinion 42. The nozzle 12 is mounted on this pinion 42 in such a manner that the nozzle is swivelled upwards and downwards in an arc 41, as indicated in figs. 2 and 4.

The speed, which is determined by the turning angle of the adjusting arm 25 and herewith by the speed of rotation of the worm shaft 31, is determined by the position of the eccentric 29. Since this can be changed in a stepless man¬ ner, the speed can hereby be varied from a low to a higher speed, i.e. depending on the movement of the carrier arm 25 by the drive head.

In order to clarify the forwards and backwards movement of the pinion 38, the geometric relationships are depicted in fig. 4, where the pinion 38 is indicated turning around its axis 37. The connecting link 35 extends between the points of application 36 and 34 on the worm wheel 32 which turns around its axis 33.

It will be noted that the radius of the worm wheel 32 is less than the radius of the pinion 38.

With stippled lines, fig. 4 also shows the rack 39 which at its opposite end of the main shaft 23 is provided with a rack 43 which is in engagement with the nozzle's 12 pinion 42.

It appears clearly from the drawing that when the pinion 38 is moved over an angle of more than 180°, then the nozzle's pinion 42 will be made to effect a turning movement of more than 180°.

For the sake of clarity, there is sketched in a given posi-

tion of the vectors between the centres 33 and 37 and the studs 34 and 36.

By changing the radius of the worm wheel 32 to the stud 34 and the length of the connecting link 35, both the length of the swivelling movement 41 of the nozzle 12 as well as the turning angle of the nozzle 12 can be adjusted. These can hereby be adjusted for the individual tank.

The following is a description of the mode of operation of the cleaning apparatus:

In fig. 6, it is indicated with curves 40 how the intensity of the jet extends inside a tank. The cleaning apparatus is envisaged as being placed in the centre 4 at the top of the tank, and in this case the nozzle 12 is dimensioned to be swivelled in an arc of 180° from the vertical up to the vertical down.

The start position of the nozzle is upwardly-directed, and it is seen that it distributes the jet uniformly in the tank during its movement. The closeness of the curved lines 40 indicates that the nozzle is operated at a low swivel¬ ling speed. This is adjusted via the rotary disk 30 for short angular rotation over the eccentric 29, which pro¬ vides only a short rocking movement of the arm 25 and here¬ with slow rotation of the worm shaft 31 and therewith finally limited movement of the rack 39 and herewith the pinion 42, as indicated in figs. 3 and 4.

When a more dispersed cleaning pattern is desired with greater nozzle swivelling speed, the eccentric 29 must be turned towards greater angular rotation and herewith greater rocking movement of the arm 25 to produce a high speed of rotation of the pinion 42 at the nozzle.

The cleaning intensity can be steplessly adjusted to ensure adequate cleaning of the tank and no more. This is natural¬ ly of great importance for the economy, in that there is no need to clean more than necessary, and that this adjustment of the intensity can take place by stepless adjustment.

Since there is normally a need for extra cleaning particu¬ larly of the corners at the bottom, it is expedient to use a construction like that which is shown in fig. 4, where the nozzle can turn at the furthermost corners, in that the rocking movement can extend from the vertical and pointing to opposite corners.

Fig. 5 shows graphically how the nozzle 12 and herewith the jet are oriented for most of the time, the absciss, in the area between 50° and -50°, which is just above the bottom, while the 180° on the ordinate means that the nozzle points upwards for a shorter period of time.

From this it will be clear that an extraordinarily effect¬ ive cleaning is achieved of precisely those areas inside the tank which are normally the most dirty. An attempt to illustrate this is also made in fig. 6, which shows the cleaning which is achieved in the corners where the nozzle turns, and where the cleaning intensity of the jet path 40 is at its greatest.

This cleaning pattern is unique for the apparatus and pro¬ vides a hitherto-unknown high degree of efficiency, and herewith savings in both energy and cleaning fluid as well as time.

The apparatus can be provided in a commonly-known manner with indicators for the nozzle' s position both in the ver- tical and the horizontal planes, so that the starting posi¬ tion for the nozzle can be adjusted in accordance with re-

quirements before the cleaning commences.

The speed at which the nozzle is swivelled can be read from the rotary disk on the eccentric, and herewith the intens- ity of the cleaning pattern.

Where there is need for a programmed control of the clean¬ ing pattern, the eccentric can be made rotatable by means of a servo motor, whereby an adjustment and regulation can be effected for achieving the most expedient cleaning for the individual tanks.