| GB2019346A | 1979-10-31 | |||
| FR417340A | 1910-11-11 | |||
| EP0754865A2 | 1997-01-22 | |||
| US5486092A | 1996-01-23 |
| 1. | Loading device for a vacuum tank vehicle designed primarily for the transport of heavily contaminated liquids, such as liquid slurries, incorporating a vacuum pump (2 in Fig. 1) to create a partial pressure in the tank (1 in Fig. 1), an overflow valve (5 in Fig. 1) and at least one suction line (3 in Fig. 1) connected to the tank (1) at one end and immersed in the liquid in question at the other end, c h a r a c t e r i s e d i n t h a t a centrifugal pump (4 in Fig. 1) driven by a hydraulic motor is fitted to the end of the suction line (3) immersed in the liquid, the housing (4b in Fig. 2) and discharge opening (4c in Fig. 2) of the said pump being considerably wider than the pump impeller (4a in Fig. 2). |
| 2. | Device as per patent claim 1, in which the vacuum tank vehicle is drawn by an agricultural tractor, c h a r a c t e r i s e d i n t h a t the tank vehicle vacuum pump (2) is driven by the tractor's ordinary power takeoff and the hydraulically driven pump (4) is supplied with drive fluid by the tractor's ordinary hydraulicpump. |
| 3. | Device as per either of the foregoing patent claims, c h a r a c t e r i s e d i n t h a t the suction line (3) is essentially handled and manipulated manually. |
Vacuum tank vehicles of existing, known types suffer from the disadvantage that the loading process may be slow or, in the worst case, cease completely when the lift is high and when pumping liquids which are difficult to pump as described above. Since the maximum available theoretical pressure difference between the tank and pumped liquid is only one atmosphere, or one bar,. the capacity for overcoming friction and lift is limited. The lift cannot exceed a theoretical value of 10.3 metres and is limited to 6-7 metres in practice.
The present invention offers a solution to the abovementioned problems as described in the characteristic section of patent claim 1. In a device in accordance with the invention, it is advantageous if the hydraulically driven, submerge, operating pump (4 in Fig. 1) does not offer significant resistance to the flow of liquid at low lifts and high flows. Furthermore, the pump must not impair the known, high capacity of the vacuum tank vehicle to accept highly contaminated liquids without operating problems in the form of material blockages and build-up
in or at the suction line inlet. For this reason, the pump is provided with a pump housing (4b in Fig. 2) which is extra wide relative to the pump impeller (4a in Fig.
2). In this context, it should be noted that, for practical reasons, it is a common aim to ensure that the pump is not too big or too heavy.
A centrifugal pump in accordance with the invention will have a relatively low efficiency: in practice, however, it will increase the loading capacity significantly.
In an example of an embodiment of a device in accordance with the invention (Fig.
1), which embodiment is especially suitable for agricultural use, in which a vacuum tank vehicle is pulled by an agricultural tractor and its vacuum pump is driven by the tractor's ordinary power take-off (PTO), it has proved advantageous to take the motive power for the hydraulically powered pump from the tractor's ordinary hydraulic system.
Tests of the loading device in accordance with the invention have revealed another avantage in the form of a reduction in the foaming which tends to occur easily in liquid slurries and similar liquids when these are exposed to partial pressure, since only part of the loading operation is carried out under these conditions. In the case of vacuum tank vehicles of known types, it is common for the foam thus formed to close the overflow valve (5 in Fig. 1) prematurely so that the tank is not completely filled. With a device in accordance with the invention, the amount of foam is reduced. Furthermore, at least the final part of the loading operation can be carried out with the aid of the pump (4) alone, enabling the tank to be filled completely.
The invention is of particular value in applications in which the suction line (3) consists of a pipe or hose, or a combination of both, and is handled and manipulated manually, unlike those in which the suction line is controlled and manipulated with the aid of a servo-assisted crane arm. In the former instance, since priority must be given to the pliability, flexibility and lightness of the hose, the option of selecting a large-diameter hose is limited compared with crane-arm operation. If a small- diameter hose is used, the resistance to liquid flow will be high, making pump assistance extra valuable.