LIQUID STORAGE TANKS

Abstract: A slurry tanker 1 has a housing 2 which is divided by an upright internal partition 3 into a forward tank portion 4 and rear tank portion 5. The partition 3 is sealed to the walls of the housing 2, apart from an aperture 6 at the bottom of the partition 3. The forward tank portion 4 has a one-way ball valve 8. In use, the valve 8 allows air to be exhausted from the forward tank portion 4, as the tanker 1 is filled with slurry. However, as the tanker 1 is emptied, the valve 8 prevents air entering the forward tank portion 4. Thus, the rear tank portion 5 is substantially emptied before the forward tank portion 4 begins to be emptied. In this way, the weight of slurry tends to be maintained at the forward end of the tanker 1, especially when part-full. This can be especially advan­ tageous where the tanker 1 is a trailer. The invention applies both to vacuum and non-vacuum tankers.

Description: LIQUID STORAGE TANKS This invention relates to liquid storage tanks, and is concerned particularly although not exclusively with slurry tankers. Slurry tankers are well known in the field of agriculture, for the transport and spreading of liquid manure. Typically, slurry tankers are in the form of cylindrical tanks which are carried on trailers, adapted to be towed behind tractors. One of the problems that may be encountered when towing a partly filled slurry tanker is that, when going uphill, the liquid contents fall towards the back of the slurry tanker, thus taking weight off the driving wheels of the tractor. Thus, especially in wet going, the tractor may lose traction. Preferred embodiments of the present invention aim to provide slurry tankers which may be improved in this respect. More generally, according to a first aspect of the present invention, there is provided a liquid storage tank comprising a closed housing having a base and divided by an upright internal partition into two tank portions which communicate with one another only at or towards said base, outlet means at or towards said base for the outlet of liquid from the tank, and valve means for selectively venting an upper part of one of said tank portions. Said valve means preferably comprises a one-way valve adapted only to exhaust gas from said one tank portion. Said housing may be elongate, with said partition extending transversely of said housing. Sai housing may be cylindrical In an advantageous arrangement, said housing is carried on a vehicle. The said tank portions may be disposed respectively fore and aft of the vehicle. Preferably, said one tank portion is disposed fore of the vehicle. The invention may be applied with particular advantage to a trailer which is provided with a tank in accordance with the first aspect of the invention. Such a trailer may be a slurry tanker. For a better understanding of the invention and to show how the same may be carried into effect, reference will now be made, by way of example, to the accompanying diagrammatic drawing, in which: Figure 1 is a longitudinal section of a slurry tanker embodying the invention; Figure 2 is a section taken on the line 11-Il of Figure 1; and Figure 3 shows another slurry tanker, In longitudinal section. The slurry tanker 1 that is shown in Figures 1 and 2 comprises a closed elongate housing 2, which is generally oval in cross-section. The housing 2 is divided by an upright internal partition 3 into a first tank portion 4 and a second tank portion 5. The partition 3 is joined to the internal walls of the housing 2 around its periphery, in a fluid-tight manner, apart from an aperture 6 which is provided at the bottom of the partition 3, towards a base 7 of the housing 2. Thus, the two tank portions 4 and 5 communicate with one another via the aperture 6 but, apart from this, are separated in a fluid-tight manner. The first tank portion 4 is provided on the upper wall of the housing 2 with a one-way ball valve 8, which allows air only to be exhausted from the first tank portion 4. The ball valve 8 is situated towards the rear of the first tank portion 4. The second tank portion 5 is provided with a filler point 9, and with a discharge pump 10 feeding an outlet pipe 11, in a generally conventional manner. The housing 2 is mounted on a suitable chassis which is supported on a pair of land wheels 12, and is provided with a towing bar 13, by means of which the slurry tanker 1 may be towed behind a tractor. The illustrated slurry tanker 1 operates as follows. Firstly, the slurry tanker 1 is hitched to the draw bar of a tractor, by means of the towing bar 13. Then, when empty, the slurry tanker 1 is filled in a conventional manner, by pouring slurry into the housing 2, via the filler point 9. It will be appreciated that, as the slurry enters the housing 2, it progressively fills up both the first and second tank portions 4 and 5. As the first tank portion '4 is being filled, air is exhausted therefrom via the one way ball valve 8. Of course, as the second tank portion 5 is being filled, air is vented therefrom in a conventional manner, via the filling point 9. When the tanker 1 is full, the filling point 9 is closed. The slurry tanker 1 may then be towed to a desired point, and the slurry discharged by means of the pump 10 and via the outlet pipe 11. It will be appreciated that, when the pump 10 first begins to operate, slurry is discharged initially from the second tank portion 5. As the slurry is discharged, air enters the second tank portion 5 via the filler point 9, which provides sufficient venting for this purpose. For as long as the level of the slurry in the second tank portion 5 stays above that of the aperture 6, the first tank portion 4 remains full of slurry. This is because the one-way ball valve 8 serves to prevent venting of the first tank portion 4. Thus, when partly full, the slurry within the housing 2 may be distributed generally as illustrated in Figure 1. This provides the advantage that, even when the tractor is going uphill, the weight of the slurry remains principally applied to the rear wheels of the tractor, thereby to assist traction. In conventional slurry tankers, the weight of the slurry tends to be transferred to the rear of the trailer when going uphill, thereby removing weight from the driven tractor wheels, and thereby reducing traction. Thus, the illustrated slurry tanker' I may be much improved in this respect. uhen the level of slurry in the second tank portion 5 falls to the level of the aperture 6r then air may pass from the second tank portion 5 to the first tank portion 4, allowing the slurry to be progressively discharged from the first tank portion 4. Preferably, the ball valve 8 is manually releaseable, to allow the first tank portion 4 to be vented to atmosphere at any time, should it be desired to equalise the distribution of slurry within the tank portions 4 and 5 or, indeed, to allow the weight of the slurry to be taken off the driven tractor wheels, when in an uphill position. The slurry tanker 20 which is shown in Figure 3 is similar in a number of respects to the previously described slurry tanker, and in the figures, like reference numerals denote like or corresponding parts. In Figure 3, however, the housing 2 of the slurry tanker 20 is divided by means of two partitions 3 into first, second and third tank portions 24, 25 and 26. The slurry tanker 20 is a vacuum tanker, provided with a vacuum pipe 21, which is adapted to supply air under positive or negative pressure to the tank portions 24, 25 and 26. To this end, the vacuum pipe 21 communicates directly with the upper part of the third tank portion 26, and via the upper portions of the first and second tank portions 24 and 25 via respective valves 22 and 23. A discharge pipe 27 has an inlet 28 disposed in the first tank portion 24, and an outlet 29 disposed above the housing 2 at the rear thereof, and adjacent a spreader plate 30. A gate valve 31 is adapted to open and close the discharge pipe 27, under the control of a pneulaatic ram 32. A filler pipe 33, which is provided with a respective valve 34, communicates with the first tank portion 24. The slurry tanker 20 operates as follows. Firstly, it is hitched to a tractor by means of the towing bar 13, in a conventional manner. Then, when empty, the gate valve 31 is closed, all of the valves 22, 23 and 34 are opened, the filling point 33 is connected to a reservoir of slurry, and the vacuum pipe 21 is connected to negative pressure. Thus, it will be a##preciated, all cf the tank portions 24, 25 and 26 are subjected to negative pressure, causing slurry to be sucked into the housing 2, via the filling point 33. When the tank portions 24, 25 and 26 are full, the valve 34 is closed, the valves 22 and 23 are then closed, and the supply of negative pressure to the vacuum pipe 21 is terminated. The slurry tanker 20 is then towed to a desired location. In order to discharge slurry from the tanker 20, positive air pressure is supplied to the vacuum pipe 21, and the gate valve 31 is opened. The slurry is then forced out of the discharge pipe 27, under the influence of the positive air pressure It will be appreciated that, initially, slurry is displaced only in the third tank portion 26, which is the only one in direct communication with the positive air pressure supply from the vacuum pipe 21. This continues for as long as the level of slurry in the third tank portion 26 is above the level of the aperture 6 in the respective partition 3 which separates the second tank portion 25 from the third tank portion 26 in an otherwise fluid-tight manner. Thus, as in the preceding embodiment, the weight of slurry may be maintained principally of the driven tractor wahols, even when .ing uphill. As soon as the level of slurry in the third tank portion 26 falls to the level of the respective-aperture 6, then the positive air pressure begins to prevail in the second tank portion 25, which then begins to empty progressively. In a similar manner, the first tank portion 24 remains full of slurry until the level in the second tank portion 25 falls below that of the aperture 6, after which the first tank portion 24 begins to empty progressively. It will be appreciated that the tank portions 24, 25 and 26 may selectively be equalised at any time, by appropriate actuation of the valves 22 and 23. The valves 22 and 23 may be one-way valves, similar to the ball valve 8 of Figure 1, for example. Thus, they may open automatically when a negative pressure prevails in the vacuum pipe 21, and close automatically when positive pressure prevails in the vacuum pipe 21. Thus, both of the illustrated embodiments provide slurry tankers 1 and 20 which may be operated in a largely conventional manner, except that they provide the facility for retaining the weight of slurry over the driv n tractor wheels when the tanker is part-filled, even when going uphill. A particular feature of the illustrated embodiments is the ease with which this facility may be provided. In this respect, it is to be appreciated that slurry takers are often provided with reinforcing baffles extending transversely of the tanker housing, to reinforce the tanker housing and to dampen oscillations of slurry in the tanker, during travel. All that is required is to substitute for such a baffle in a slurry tanker an upright partition such as is illustrated in Figures 1 and 2, to SePal ate the housing into the two portions 4 and 5 which corl;municate only via the bottom aperture 6, and then to provide the one-way valve 8 in the upper wall of the housing 2. Similarly, the embodiment of Figure 3 may be provided in a very simple manner. It will therefore be appreciated that the present invention may be provided at very little additional cost. Moreover, existing slurry tankers may readily be converted to provide the fca t urc s of the invention, and the invention extends to methods of so modifying existing slurry tiillkers. The invention is not restricted to the details of the foregoing embodiment(s). The invention extends to any novel one, or any novel combination, of the features disclosed in this specification and/or drawings, or to any novel one, or any novel combination, of the steps of any method or process disclosed herein.

Claims: CLAIMS: 1. A liquid storage tank comprising a closed housing having a base and divided by an upright internal partition into two tank portions which communicate with one another only at or towards said base, outlet means at or towards said base for the outlet of liquid from the tank, and valve means for selectively venting an upper part of one of said tank portions. 2. A tank according to Claim 1, wherein said valve means comprises a one-way valve adapted only to exhaust gas from said one tank portion. 3. A tank according to Claim 1 or 2, wherein said housing is elongate, and said partition extends transversely of said housing. 4. A tank according to Claim 1, 2 or 3, wherein said housing is cylindrical. 5. A tank according to any preceding claim, wherein said housing is carried on a vehicle. 6. A tank according to Claim 5, wherein said tank portions are disposed respectively fore and aft of the vehicle. 7. A tank according to Claim 6, wherein said one tank portion is disposed fore of the vehicle. 8. A trailer provided with a tank according to Claim 5, 6 or 7. 9. A trailer according to Claim 8, being a slurry tanker. 10. A liquid storage tank substantially as hereinbefore described with reference to the accompanying drawings.

Inventors: LUND, JOHN BRIAN
Applicants: LUND, JOHN BRIAN
Application year: 1986
Main classification: B60P3
IPC codes: A01C23