EP0715691B1 - Torque-compensated centrifugal pump - Google Patents

Description

The present invention relates to a pumping system including a submersible centrifugalpump in which the reaction moment of the pump impeller will be opposed in a manner advantageous to the practipal handling of the pumping system.

The appended figures relating to the following description of the invention are:

Fig.1, which shows the pump from the suction (inlet) side when operating lightly loaded;

Fig.2, which shows the pump in the same view as Fig.1 when operating at a heavier, continuous load;

Fig.3, which shows the pump in the same view as Figs. 1 and 2, but in a version designed especially for heavy load;

Fig.4, which shows the pump in a schematic view at 90° to Figs. 1, 2 and 3.

Simple centrifugal pumps driven by submersible eletric or hydraulic motors mounted more or less directly on the pump housing are already known ; see, for example, FI-B-54 185. These pumps suffer from the disadvantage of a reaction moment about the impeller axis, which tends to turn (rotate) the entire pump housing in the opposite direction to the impeller rotation, often making it necessary to make fast the pump to the bottom or side walls of the pit, or to use a strong rigid, torque-resistant iron pipe or simular component as discharge line from the pump, and to make fast this line. In the agricultural sector in particular, it may often be desirable to use a readily flexible component (i.e. a hose), connected directly to the pump, as discharge line, enabling the line to be rolled up, with the pump and motor still attached to the end, in order to transfer the complete assembly from one application site to another. The main purpose of the present invention is to achive a pumping system including a submersible centrifugal pump with motor and impeller, where the reaction moment on the pump housing caursed by the impeller drive torque is opposed in a manner allowing the pump to be installed and to operate just through suspention from a hose without any other means or attachment. The hose preferably serving also as flow discharge line from the pump. This is achieved by arranging the pump impeller (1 Fig.1), to operate vertically submerged in the liquid with its shaft entering the motor (5, Fig.4), horizontally, and by connecting the hose (4, Fig.1) to the pump housing (2, Fig.1), or to a from the pump housing outgoing rigid fastend rigid element (7, Fig.3), at a specified vertical distance (r, Fig.1) from the pump impeller axis. Whereby the complete pump swings relativ to the hose (4) when the load (torque) increases, in such manner that the horizontal distance (s, Fig.1) beetwen the center or gravity of the pump (Tp, Fig.2) and the connection point (3, Fig.2) of the nose (4) to the pump housing (2) or to the rigid element (7) increases by the distance (s', Fig.2), which multiplied by the weight of the pump, creates a moment opposed to that due to the impeller drive torque.

According to the symbols in the Figs, the following are valid: The dead weight ot the pump (g, Fig.1)) acting at (Tp, Fig.1), multiplied by the lever (s, Fig.1) or (s + s', Figs.2 and 3) create a moment about the hose connection (3, Fig.2), counteracting that created about the same point (3) by the pump impeller torque.

At heavy load, the pump housing (2, Fig.3) may suitably be provided with an outgoing rigid fastend rigid element (7, Fig.3). This element can be designed as an outlet section which is longer than that required to connect the hose (4) securely by means or a hose clip. The outlet section may consist, for example, of a welded-on iron pipe, to which the hose (4) is connected essentially above the centre of the pump impeller. The adventage of this arrangement is that when the pump swings sideways relativ to the hose (4) as the torque increases, than can the distance (s) increase substantially without causing excessively sharp bending of the hose (4) (see Fig.).This also affords a more stable equilibrium point to the pump when its operating since the opposing force produced by a bent, heavy (big) hose is difficult to define.

Several pumps in accordance with the invention have been built and tested in practical operation. In particular, small achievements for flows of up to a few m³/ min and pressures up to about one bar can be made extremely flexible, easy to operate and easy to install in that they can be transferred manually between different application sites. In this context, hydraulic motors, which are driven by agricultural tractors, are preferable because of their low weight-to-power ratio. Although most present-day light hoses also possess acceptable tensile strength, they cannot withstand any considerable twisting moment, as would be the case it a centrifugal pump operating with its impeller horizontal (the shaft vertical) where installed just through suspention from a hose. The best example of this is provided by the otherwise convenient and inexpensive flat coiled hose, of the type used for example by fire brigades, which tends to twist when the least torsional force is applied. In constructing the pump, it has also been found advantageus to make the rigid pipe (7) approx. 10-50 cm in length, depending on the pump size. The invention may, of course, be varied within the framework of the patent claims; for example, the arrangement described for large moment may also be obtained even in the case when the hose (4) is connected directly to the pump housing, by provideing the pump housing with some other rigidly protruding rigid element other than the outlet pipe (7), to which the hose is secured essentially above the centre of the pump impeller, for example clamped on the outside or the hose by means of an external hose clip. Another possible alternative is to suspend the pump from one or both of the hoses through which the fluid for the hydraulic drive motor flows (6, Fig.4) and to secure that/them to the aforesaid rigid element some distance up.

Claims (3)

1. Pumping system including a centrifugal pump equipped with an impeller (1), which in use together with an hydraulic drive motor (5) is submerged in the liquid to be pumped, with hoses going down to the pump (4,6) for the pumped liquid and the hydraulic drive motor, at least one of which is secured to the pump or to an from the pump rigidly extending rigid element, such that it is essentially pulled straight between its upper attachment point and the pump or the element
   characterised in that the pump impeller (1) runs essentially vertical orientated ie. with the shaft entering the motor (5) horizontally and the above mentioned straight hose is secured to the pump, or to the rigid element at a specified vertical distance (r) from the centre of the impeller in such manner that the reaction moment on the pump caused by operation of the impeller is counteracted.
2. Arrangement in accordance with patent claim 1,
   characterised in that the rigid element consists of a pipe, forming an extended discharge branch (7).
3. Arrangement in accordance with patent claim 1,
   characterised in that the rigid element consists of an extended organ other than a discharge branch to which the outside of the hose is secured.

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