GB2097485A

GB2097485A - Pumping device

Info

Publication number: GB2097485A
Application number: GB8211992A
Authority: GB
Original assignee: Philips Gloeilampenfabrieken NV
Current assignee: Koninklijke Philips NV
Priority date: 1981-04-29
Filing date: 1982-04-26
Publication date: 1982-11-03
Also published as: ES264770Y; CA1180977A; IT8220938A0; FR2504990B1; ES264770U; FR2504990A1; SE8202572L; IT1151326B; GB2097485B; JPS57176699U; NL8102103A; DE3214882A1

Abstract

A pumping device for lifting a small volume of liquid through a large height comprises a diaphragm pump (1) with a work-dependent stroke, and an inlet valve and an outlet valve to which a suction line and a discharge line (2, 3) respectively are connected. In order to increase the head of liquid provided by the pump an air-supply line (6) is connected to the suction line so that the diaphragm alternately sucks in air and liquid. This reduces the flow rate but provides an increased head of liquid.

Description

SPECIFICATION Pumping device The invention relates to a pumping device for lifting a liquid, which device comprises a diaphragm pump having a work-dependent stroke, and an inlet valve and an outlet valve to which a suction line and a discharge line respectively are connected.

A problem with such pumping devices is that the diaphragm pump can provide only a small head of liquid.

It is an object of the invention to provide a pumping device of the above type in which the head of liquid can be increased by simple and cheap means.

According to the invention there is provided a pumping device for lifting a liquid, which device comprises a diaphragm pump having a workdependent stroke, and an inlet valve and an outlet valve to which a suction line and a discharge line respectively are connected, wherein an air-supply line is connected to the suction line. The diaphragm pump alternately sucks in air and liquid. This reduces the flow rate but on the other hand it provides an increased head of liquid.

If the diaphragm pump is switched off for a prolonged period, air will rise up through the liquid columns in the suction and/or the discharge line, so that when the pump is started again it may not be capable of lifting the liquid.

In order to solve this problem in one embodiment of the pumping device in accordance with the invention an initial part of the discharge line extends downwards from the outlet valve. As a result of this the pump becomes self-priming.

In another embodiment at least one liquid trap is arranged in the suction line between the airsupply line and the diaphragm pump.

Preferably, the liquid trap is constituted by a circular loop in the suction line.

The pumping device may be used in those cases where small volumes of liquid have to be lifted though a comparatively large delivery height, such as in drainage of condensation water in heat-pump boilers, and in cellar pumps.

Embodiments of the invention will now be described in more detail with reference to the accompanying drawings, in which: Figure 1 is a diagrammatic side elevation of a pumping device in accordance with one embodiment of the invention, Figure 2 is a sectional view of the diaphragm pump of the pumping device of Figure 1, Figures 3 and 4 show a pumping device in which the pump discharges against a head of liquid and is self-priming, and Figures 5 and 6 show a pumping device in which the pump sucks against a head of liquid and has liquid traps in the suction line.

The pumping device of Figure 1 comprises a diaphragm pump 1, to which a suction line 2 and a discharge line 3 are connected. The end 4 of the suction line is located in a reservoir 5 containing a liquid which is to be pumped up. An air-supply line 6 is connected to the suction line. The diaphragm pump 1 shown in Figure 2 is of a generally known type and is constituted by a vibrator motor 7, comprising a stator 8, a coil 9 and an armature 10 which is pivotably supported in the pump housing, and by a diaphragm 11, which is connected to the armature 10, and by a pump chamber 12 having oppositely acting inlet and outlet valves 13 and 14 respectively. In such diaphragm pumps the length of the stroke of the armature depends on the amount of work required.

The operation of the pumping device is as follows: the pump sucks in air via a narrow airsupply line 6. However, because the pump demands more air than the line can supply due to its flow resistance, the pump also sucks up liquid from the reservoir 5. The pump now pumps the mixture of liquid and air and since this demands more power the pumping efficiency will be reduced. As a result of this the suction will also be reduced, so that the pump only sucks in a small amount of air. If the water is drained from the pump chamber 12, even more air will be sucked in. This gives rise to a reduced pressure in the suction line and the process is repeated.

Alternately air and liquid are sucked in and pumped up. The head of liquid is consequently much greater than in the absence of the airsupply line.

When the pumping process is stopped it is found that after some time the liquid in the discharge line 3 drops to a lower level because the air slowly escapes up through the liquid columns in the line 3. Consequently, above the outlet valve 14 a continuous or "solid" liquid column is formed. When the pump is switched on this "solid" liquid column cannot be forced away by the pump. To overcome this an initial part of the discharge line 3 extends downwards from the outlet valve 14. In Figure 3 this initial part of line 3 is constituted by a semi-circular loop 1 5 in the discharge line itself. The loop should therefore be situated at a lower level than the pump.If the pumping process is stopped for some hours this again gives rise to a "solid" liquid column 16, but between this "solid" liquid column and the outlet valve 14 an air column 17 is maintained, because here the loop 15 extends upwards (see Figure 4).

As a result of this compressible air column the pumping process is normally started when the pump is switched on. Successful tests have been made with a pumping device having the following specification: Pumping power approx. 2.7 W Inner suction line diameter: 3.5 mm Inner discharge line diameter: 3.5 mm Inner supply line diameter: 1.2 mm Difference in level between reservoir and pump: 30 cm Head: 4.2 m Capacity: 1.5 I/h Figure 5 shows a pumping device in which the liquid is sucked from a low level to a high level, the pump being situated at the higher level. When this difference in level, that is, the head, is very large, some air will escape up the liquid columns during pumping. In order to overcome this problem, one or more liquid traps is or are arranged in the suction line 2. The liquid traps, as is shown in Figures 5 and 6, may be constituted by circular loops 18 in the suction line. The liquid collects in these loops so that the liquid is drawn up in a more or less stepwise manner. The number of loops depends on the desired head.

Other forms of liquid trap may be used instead.

This pumping device is also self-priming, that is to say if the pump has remained inoperative for a prolonged period and is then switched on again, immediate suction is obtained (see Figure 6). This pumping device, with the following specification has also been tested with success: Pump power 2.7 W Inner suction line diameter: 3.5 mm Inner air-supply line diameter: 1.2 mm Distance between the loops: approx. 50 cm Head: 4.2 m Capacity: 1.2 I/h

Claims

1. A pumping device for lifting a liquid, which device comprises a diaphragm pump having a work-dependent stroke, and an inlet valve and an outlet valve to which a suction line and a discharge line respectively are connected, wherein an air-supply line is connected to the suction line.

2. A pumping device as claimed in Claim 1, wherein an initial part of the discharge line extends downwards from the outlet valve.

3. A pumping device as claimed in Claim 1 or 2, wherein at least one liquid trap is arranged in the suction line between the air-supply line and the diaphragm pump.

4. A pumping device as claimed in Claim 3, wherein the liquid trap is constituted by a circular loop in the suction line.

5. A pumping device substantially as herein described with reference to Figures 1 and 2 or Figures 2, 3 and 4 or Figures 2, 5 and 6 of the accompanying drawings.