EP0715691A1

EP0715691A1 - Torque-compensated centrifugal pump

Info

Publication number: EP0715691A1
Application number: EP94925659A
Authority: EP
Inventors: Bengt Olsson
Original assignee: Individual
Current assignee: Individual
Priority date: 1993-08-25
Filing date: 1994-08-16
Publication date: 1996-06-12
Anticipated expiration: 2014-08-16
Also published as: SE9302739D0; SE503575C2; DE69421931D1; DE69421931T2; DK0715691T3; EP0715691B1; WO1995006206A1; SE9302739L

Abstract

Device for a hydraulic motor-driven, submersible, centrifugal pump operating while suspended, preferably from the hose which serves as discharge line from the pump, the pump impeller (1), figure 1, being installed vertically and the shaft horizontally, with the hose connected to the pump in such manner that a specified horizontal distance (s) from the centre of gravity (Tp) of the pump is established or occurs when the pump is running under load. Together with the weight (g) of the pump, this lever (s) creates a moment which opposes that due to the braking action of the liquid on the pump impeller.

Description

TORQUE-COMPENSATED CENTRIFUGAL PUMP

The present invention relates to a device for a submersible centrifugal pump, in which the reaction moment of the pump impeller is accommodated in a manner advantageous to the practical operation of the pump.

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 electric or hydraulic motors mounted more or less directly on the pump housing are already known. These pumps suffer from the disadvantage of a reaction moment about the impeller axis, which tends to swing the entire pump housing in the opposite direction to impeller rotation, often making it necessary to make fast the pump to the bottom or side walls of the pit, or to use a rigid, torque-resistant iron pipe or similar component as discharge line, 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 purpose of the present invention is to achieve a submersible centrifugal pump in which the reaction moment on the pump housing is accommodated in a manner allowing the pump to operate freely suspended from a hose in the liquid to be pumped, 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) at a specified horizontal distance (s) from the centre of gravity (Tp) of the pump, in such manner that the dead weight (g) of the pump and the lever (s) create a moment about the hose connection, counteracting that created about the same point by pump rotation. At equilibrium, Mv (impeller reaction) = g x s (see Fig. 1 for direction of rotation of impeller). In practice, it is also advantageous to connect the hose (4) to the pump housing (2) at a specified vertical distance (r) from the pump impeller axis, allowing the complete pump to swing relative to the hose (4) when the torque increases, in such manner that the lever (s) increases by (s') (see Fig. 2). If the torque is increased further, the pump housing (2), Fig. 3, may suitably be provided with a rigid outlet section (7) which is longer than that required to connect the hose (4) securely by means of a hose clip. This 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 advantage of this arrangement is that when the pump swings sideways relative to the hose (4) as the torque increases, the distance (s) increases substantially without causing excessively sharp bending of the hose (4) (see Fig. 2). This also affords a more stable equilibrium point when the pump is operating since the opposing force produced by a bent, heavy hose is difficult to define. Several pumps in accordance with the invention have been built and tested in practical operation. In particular, small installations 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 a high twisting moment, as would be the case if a centrifugal pump were installed with the impeller horizontal and the shaft vertical, suspended from and supported only by 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 advantageous to make the rigid pipe (7) approx. 10-50 mm 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 moments may also be implemented in the embodiment in which the hose (4) is connected directly to the pump housing, by employing some rigid outlet element, other than the outlet pipe (3), connected rigidly to the pump housing, to which the hose is connected essentially above the centre of the pump impeller, for example by means of an external hose clip. Another possible alternative is to suspend the pump from the hoses (6), Fig. 4, through which the hydraulic motor fluid is supplied and to secure the aforesaid rigid element to these some distance above their connection point.

Claims

Patent claims

1. Device for a torque-compensated centrifugal pump which, together with its driving hydraulic motor, is submerged in the liquid to be pumped, the pump being suspended from one or more hoses connected to the pump, characterised in that the pump impeller (1), Fig.1, operates basically vertically with the shaft entering the motor (5), Fig.4, horizontally and that the hose (or hoses) (4), Fig.1, is connected to the pump housing (2) at a specified vertical distance (r) from the impeller axis, whereby the complete pump swings with respect to the hose (4) when the pump impeller torque is increased (see Fig.2), in such manner that the horizontal distance between the connection point (3) of the hose (4) to the pump housing and the centre of gravity (Tp) of the pump increases by the distance (s') which, multiplied by the weight of the pump, creates a moment opposed to that due to the impeller drive torque.

2. Device in accordance with patent claim 1., characterised by a rigid outlet element (7) connected rigidly to the pump housing (2), Fig.3, and connected to a hose (or hoses) (4) essentially above the pump housing, such that the lever (s') may increase substantially without causing excessively sharp bending of the hose (4).