Diaphragm Pumps With Pressure Equalising Chambers

Abstract

A diaphragm pump which can function as a pressure pump or a suction pump and which is for use in aerating aquaria or in medical and industrial apparatus, has a pump housing which is longer in one direction than in another and which is divided longitudinally to form a pump chamber in which the pumping mechanism is located and a pressure equalising chamber through which the pump output is passed. The division of the housing longitudinally to provide an elongated pressure equalising chamber is very effective in providing the pump with a fairly continuous and relatively silent output, particularly when the effective distance between the inlet and the outlet of the equalising chamber is at least half the length of the chamber.

Description

This invention relates to diaphragm pumps which can function as a pressure pump or a suction pump, and which are commonly used for aerating aquaria and for medical and industrial apparatus, the pumps having a pressure equalising chamber for equalising the pressure of the output from them.

The moving parts of such diaphragm pumps usually consist only of a diaphragm, two valves and an oscillating armature, fluid being sucked into the pump through one of the valves on one stroke of the diaphragm and expelled through the other valve on the other stroke, the two valves acting 180.degree. out of phase. That is, during the period when the fluid is flowing through the one valve the other valve remains closed, and vice versa. The valves are usually simple flap valves, or the equivalent. A pump of this kind has several advantages. There are very few moving parts and are therefore extremely simple, and the pump requires very little maintenance. On the other hand diaphragm pumps have the disadvantage that they are often very noisy, the noise level increasing with increasing pump output.

In an attempt to reduce the noise it is known to pass the pump output through a pressure equalising chamber. The pump housing is usually cylindrical and the known type of pressure equalising chamber is situated in one end of the housing. This arrangement is however so ineffective that it has hardly been used in practice.

The aim of the present invention is to provide a diaphragm pump which operates much more silently and which delivers the fluid substantially evenly and with good efficiency, and according to the invention this is achieved by having a pump housing which is longer in one direction than it is in another and which is divided longitudinally to form the pressure equalising chamber.

This results in an elongated pressure equalising chamber in which the pressure pulses from the diaphragm pump are largely damped out. A particularly good effect is obtained by subdividing the pump housing approximately in the ratio of at least 1:5, the smaller part being arranged as the pressure equalising chamber. In further development of the invention the functioning of the pressure equalising chamber is improved still further if the effective distance between the inlet opening of the pressure equalising chamber and its outlet opening is at least half the length of the chamber. This prevents pressure pulses from travelling directly across the chamber from the inlet opening to the outlet opening. If the inlet opening is situated near the outlet opening, the effective separation can be obtained by connecting a tube to at least one of the openings so that it extends within the pressure equalising chamber for a sufficient distance from the other opening.

The use of a separating tube makes it possible to position the inlet and outlet openings of the pressure equalising chamber opposite each other, so that the inlet opening and the neighbouring wall of the pump housing are therefore readily accessible when the pump is being assembled. In this case, the outlet opening is preferably fitted with a connecting piece having an external connector and an internal connector which communicates with the external connector and which is connected to the separation tube which extends longitudinally within the pressure equalising chamber for a distance of at least half the length of the chamber.

The connecting piece is a press fit in the wall of the pump housing, ensuring a sufficient seal between the connecting piece and the pump housing. Further advantages are obtained, in regard to the functioning of the pressure equalising chamber and in regard to assembly of the diaphragm pump and manufacture of the pump housing, in that the pump housing is in the form of a rectangular box with a cover, the contact surfaces between the cover and the body of the pump housing extending over the pressure equalising chamber. The pressure equalising chamber is therefore just as accessible, for example for cleaning purposes, as are the other parts of the pump housing.

The cover has to be well sealed, because it forms a closure both for the pressure equalising chamber and for the other part of the pump housing, i.e., the pump chamber. Preferably therefore, the cover is sealed by a sealing plate which is approximately the same size as the cover to compensate for inaccuracies in assembly or the like. The cover has at least one opening leading into the interior of the pump housing, for example for admitting air for aerating an aquarium into the pump chamber, these openings of course not communicating with the pressure equalising chamber.

It has been found in practice that the pressure equalising chamber need not extend over the entire length of the pump housing. To obtain the desired effect it is sufficient if the pressure equalising chamber extends for approximately two-thirds of the length of the pump housing.

In the case of a double-diaphragm pump, i.e., where the pumping parts are duplicated, the pump housing is divided longitudinally into at least one pump chamber and a common pressure equalising chamber. This common pressure equalising chamber is preferably formed by a pair of chamber sections which communicate with each other and which are formed by a number of longitudinal division walls in the pump housing. The connecting duct connecting the pressure equalising chamber sections together preferably has the same cross-sectional shape and area as the sections, and the two chamber sections together with the connecting duct preferably form a U-shaped chamber.

There may be two pump chambers separated from each other by a longitudinal division wall, which may or may not have one or more openings through it, or if desired, a common pump chamber can be used.

It has been found in practice that the pump in accordance with the invention functions equally well as a pressure pump or as a suction pump. Conversion from the one method of operation to the other is done without any modification of the relative positions of the oscillating arms and the magnets, as is necessary in known pumps.

Two examples of diaphragm pumps in accordance with the invention will not be described with reference to the accompanying drawings, in which:

FIG. 1 is a diagrammatic representation of a single-diaphragm pump in accordance with the invention;

FIG. 2 is a section through a part of FIG. 1;

FIG. 3 is a section taken along the line III -- III in FIG. 2 and showing more detail of the part; and,

FIG. 4 is a diagrammatic representation of the pump housing of a double-diaphragm pump in accordance with the invention.

The diaphragm pump shown in FIG. 1 has a rectangular housing 1 which is subdivided by a longitudinal wall 2 into a pump chamber 3 and a pressure equalising chamber 4. The pump chamber 3 contains an AC electromagnet consisting of a coil 6, and a core 5, and a pair of pole pieces 9. These pole pieces co-operate with a permanent magnet armature 7 which is fixed to the end of an arm 8 so that the armature 7 can oscillate in the pump chamber 3 at the frequency of the AC magnet 5, 6, 9. The coil 6, the core 5, the pole shoes 9, the oscillating armature 7 and the arm 8 together form a motor for driving the pump. The actual pumping part of the pump has a pump body 13 which is attached by a screw 12 to the wall 2 which separates the chamber 3 from the pressure equalising chamber 2. There is also a rubber diaphragm 11, which is driven in oscillation with the arm 8 which extends through a projection 10 at the rear of the diaphragm 11. The pump diaphragm 11 co-operates with the body 13 and pumping chamber 52 which communicates through an opening 14 in the wall 2 with the pressure equalising chamber 4.

Between the pump body 13 and the wall 2 there is interposed a sealing plate 40, as shown in FIGS. 2 and 3. The sealing plate 40 has a raised annular rib 41 which seals around one end of the pump body 13. The sealing plate also has a central opening 42 for the passage of the mounting screw 12, and two further openings 43 and 44. The opening 43 registers with the opening 14 in the wall 2, and the pumping chamber 52 in the interior of the pump body 13 communicates through the openings 43 and 14 with the pressure equalising chamber 4. The opening 44 is an inlet port for the actual pumping part, the opening 44 communicating the interior of the pump body 13 with the rest of the interior of the pump chamber 3. The opening 44 is a comparatively large opening, extending outwards to beyond the outer edge of the raised rib 41 and inwards to beyond the inner edge of the body 13 where it overlaps a passage 45 of the pump body 13 which will be called the suction passage.

Flow through the suction passage 45 and into the pumping chamber 52 is controlled by an inlet valve plate 46 which is centralised and guided in a recess 48 in the pump body 13, the valve plate 46 being retained by a rubber plug 47 at one of its ends.

Flow out of the pumping chamber 52 and through the opening 43 of the pump is controlled by an outlet valve plate 49 which, in a similar manner as the inlet valve 46, is retained by a plug 50 and guided in a recess 51 in the pump body 13. However, the plug 50, in contrast to the rubber plug 47, is formed integrally with the sealing plate 40, and this considerably simplifies manufacture of the pump.

The opening 14 in the intermediate wall 2 functions as the inlet opening of the pressure equalising chamber 4. This chamber has an outlet opening 15 situated in the wall of the pump housing 1 nearly opposite the inlet opening 14. To facilitate assembly of the pump body 13, together with other parts, there is a comparatively large circular opening in the wall of the pump housing 1 around the outlet opening 15, and a connecting piece 16 is inserted as a close fit in the large opening. The connecting piece 16 is formed by a press operation and has, projecting from its outer surface, a connector 17 containing the outlet opening 15, and an extension tube may, if desired, be connected to the connector 17. A further connector 18 projects inwards into the pressure equalising chamber 4 from the inside of the piece 16 and mounted over the inner end of the connector 18 is a length of stiff tubing 19 which extends almost as far as the remote end of the pressure equalising chamber 4. Consequently air entering the pressure equalising chamber through its inlet opening 14 flows along at least half the length of the pressure equalising chamber 4 before entering the end of the tube 19 and flowing through the tube and out of the pressure equalising chamber through the connectors 18 and 17.

The connector 18 is preferably bent to allow a straight tube 19 to be used and ensure that the tube 19 cannot become kinked. The connector 17 is sunk into the connecting piece 16 so that when an extension tube is mounted over the connector 17 and pushed home against the connecting piece 16 a visually clean connection is made. The connecting piece 16 can be inserted into the large opening in the wall of the pump housing 1 either by hand or by forcing it in with a mechanical, hydraulic or pneumatic tool.

The pressure equalising chamber 4 damps out the pressure pulses produced by the diaphragm pump so that, in contrast to conventional diaphragm pumps, air, for example, is delivered through the outlet opening 15 at approximately constant pressure and with negligible noise. The noise can if desired be still further reduced by filling the pressure equalising chamber 4 with a fibrous material, such as a felt, cotton wool or horsehair.

The diaphragm pump shown in FIG. 1 can be used as a pressure pump or it can, if desired, easily be converted into a suction pump by fitting the inlet opening 22 in the wall of the pump housing 1, which is shown in FIG. 1 closed by a plug 23, with a connector to which can be connected a suction line, the pump chamber 3 being well sealed against suction. The suction connector is preferably in the form of a connecting piece similar to the connecting piece 16, but without the angled inside connector 18. The suction connector is preferably of a different colour to distinguish it from the connecting piece 16 and prevent confusion between the two.

In FIG. 4 a double-diaphragm pump is shown having a pump housing 30 which consists essentially of two pump housings 1 similar to that of FIG. 1 arranged symmetrically as mirror images on either side of a symmetry axis defined by a common dividing wall 37. This wall 37 separates the two pump chambers from each other but is terminated to allow the two pressure equalising chambers to communicate. However, if desired, the wall 37 may be pierced, or the two pump chambers can communicate entirely with each other. The communicating passage between the two pressure equalising chambers is shown at 31 and has the same cross-section as the main pressure equalising chambers, i.e., the same as that of the chamber 4 of the pump housing 1 in FIG. 1. In contrast to the pressure equalising chamber 4 of the pump housing 1, the pressure equalising chamber 4 of the pump housing 1, the pressure equalising chamber of the double pump housing 30 has two inlet openings, one from each pump chamber, and also two outlet openings 15. The two pump chambers each contain a diaphragm pump and oscillating armature drive system similar in construction to those of FIGS. 1 to 3. Inlet openings 33 in the external wall of the double pump housing 30 allow air to flow into the pump chambers from where is is expelled into the pressure equalising chamber, as in the case of the diaphragm pump of FIG. 1.

The pump housings 1 and 30 are closed, when the pump is ready for operation, by covers which are not shown in the drawings. In each case the cover meets the pump housing in the plane of the drawing. The cover is a flat plate with a raised edge, the same width and length as the pump housing. The cover is screwed to the housing at the locations shown at 34 in FIG. 4, a sealing plate being interposed to make a good seal. In FIG. 4 the cover has openings indicated by chain lines at 36, near the diaphragm pumps and their oscillating armature drives.

As already mentioned these pumps can be used either as pressure pumps or as suction pumps. The effectiveness of the pump in accordance with the invention is confirmed by the surprising effect that the same pressure difference is obtained on the delivery side as on the intake side of the pump.

Claims

I claim:

1. In a diaphragm pump capable of operation either as a pressure pump or a suction pump, said pump including a housing, fluid inlet and outlet means for said housing, and a pumping mechanism including diaphragm means arranged within said housing for pumping a fluid therethrough and drive means for actuating said diaphragm means, the improvement comprising a division wall located interiorly of said housing dividing said housing internally into a pump chamber and a pressure equalization chamber, said housing being structured in a longitudinal configuration with a length dimension greater than the dimensions extending transversely thereof, said partition wall being located to extend longitudinally of said housing, means defining inlet and outlet openings to said pressure equalization chamber, the effective separation between said inlet and said outlet openings being at least half the length of said pressure equalization chamber, a separating tube and means connecting said separating tube to one of said inlet and said outlet openings of said pressure equalization chamber whereby said separating tube extends within said pressure equalization chamber for a sufficient distance to provide said effective separation between said inlet and said outlet openings.

2. A diaphragm pump as in claim 1, including means mounting said pumping mechanism on said division wall forming said pressure equalising chamber, a sealing plate interposed between said pumping mechanism and said division wall, and said pumping mechanism including a valve plate, means locating said valve plate, and plug means retaining said valve plate in location, said plug means being formed integrally with said sealing plate.

3. A diaphragm pump as in claim 1, wherein said means defining said actual inlet and outlet openings of said pressure equalising chamber are situated opposite each other in said longitudinal division wall and the wall of said housing respectively, and said separating tube extends for a distance of at least half the length of said pressure equalising chamber.

4. A diaphragm pump as in claim 3, wherein said separating tube is connected to said outlet opening, and said means connecting said tube to said opening comprises a connecting piece fitted in said opening and having an external connector and an internal connector which communicates with said external connector, and means connecting said separating tube to said internal connector.

5. A diaphragm pump as in claim 4, wherein said internal connector is bent to provide an end extending in the longitudinal direction of said pressure equalising chamber, and said separating tube is connected to said end of said internal connector.