IE49005B1 - High pressure pump - Google Patents

Abstract

A high pressure diaphragm pump has a diaphragm 2 which carries a valve poppet 7 on its upper surface. The valve poppet 7 fits into a flared portion 6 of a passage 4 for hydraulic fluid. When the diaphragm 2 restores to the position shown in Figure 1, the valve poppet 7 closes the passage 4 and prevents the diaphragm being punched back into the passage by excessive fluid pressure on the opposite side of the diaphragm. The diaphragm is made with flat edges 10, 11, 12 so that it can easily be mounted in a housing by means of three easily formed components 13, 14, 15. A small axial compression between components 14 and 15 is all that is necessary to keep the diaphragm in place during operation.

Description

This invention is concerned, with an improvement to the high pressure pumps disclosed in our O.K. latent Specification No. 1,503,122.

Experience with the pumps previously disclosed has shown that the diaphragms are at risk if the outlet, or discharge, valves fail. If a discharge valve fails, the entry of the fluid to he pumped punches the diaphragm back against the wall of the hydraulic fluid space. Hydraulic fluid enters this space through open passages, and if the diaphragm is punched back against the edges of the openings, it will wear. Under such conditions, the diaphragm may eventually rupture.

To overcome this disadvantage, it has been proposed to mount a circular component in the wall of the hydraulic fluid space, so that an annular gap is left around the edges of the circular component through which the hydraulic fluid enters the space. The edges of the component and the adjacent edges of the housing are of course rounded, but this alternative is not particularly satisfactory in that it requires an extra component of some size to be fixed in the housing and it does still leave a channel in the wall of the hydraulic space which the diaphragm can enter if it is punched back. - 2 49005 According to the invention, there is provided a high pressure diaphragm pump comprising a housing containing at least one self-restoring diaphragm, the or each diaphragm being arranged within the housing so as to separate a space for receiving hydraulic fluid from a space for receiving fluid to be pumped, the space for receiving hydraulic fluid communicating with a hydraulic fluid supply via a passage, and the diaphragm carrying a poppet on its side facing the hydraulic fluid space, for closing said passage when the diaphragm reaches the end of its intake movement.

Preferably, the passage enters the hydraulic fluid space via a flared passage portion, and the poppet fits into the flared portion to close the passage. The passage is preferably closed when there is still some hydraulic fluid remaining within the hydraulic fluid space, to act as a cushion in the event of high pressures occurring on the opposite side of the diaphragm, to prevent the central part of the diaphragm from touching any parts of the housing.

The angle of the flared passage portion and of the edges of the poppet may be 45°. This ensures that there is no chance of the poppet jamming in the passage portion when the diaphragm is required to carry out a pumping movement. - 3 49005 The diaphragm may he formed with an undercut recess which receives a flange of the poppet. Ko further fixing means are necessary.

The passage for supplying hydraulic fluid prefer5 ahly enters the hydraulic fluid space in the centre thereof, and the poppet will then be in the centre of the diaphragm.

The or each diaphragm may have a thickness to diameter ratio of at least 1:5, and· the peripheral edge of the or each diaphragm may be a right cylindrical surface, and flat annular surfaces may adjoin the cylindrical surface at the top and bottom of the peripheral edge. Such a diaphragm can be mounted in the housing within a cylindrical housing portion of diameter equal to or slightly less than the diameter of the right cylindrical surface, and be confined by surfaces exerting an axial compression on said top and bottom annular surfaces.

It has surprisingly been found that this method of fixing the diaphragm in position is quite adequate to prevent movement of the diaphragm in use. Only a small axial compression need be applied.

With this method of fixing, the housing construction can be greatly simplified because the diaphragm - 4· 48005 can be mounted within a circular bore in a plate, and the axial compression can be applied by two flat plates mounted respectively above and below the diaphragm, and pulled together by bolts.

The diaphragm is also in a shape which is easier to make than the shape shown in U.K. Patent Specification. lhe diaphragm may also be constructed with a step at the edge of its side which faces the space for receiving fluid to be pumped. When, in the prior art constructions, the underside of the diaphragm follows a continuous curve down to the bottom plate in which the inlet and discharge valves are formed, it is found that, on flattening the diaphragm, contact first occurs between the metal and the diaphragm at positions close to the edges of the diaphragm. Any contact between the moving part of the diaphragm and a metal surface should be avoided, since this leads to wear. The provision of the step prevents this contact.

The invention will now be further described, by way of example, with reference to the accompanying drawings, in which: Figure 1 is a sectional elevation through part of a high pressure pump in accordance with the invention, the lefthand half of Figure 1 being a section on line A-A of Figure 2, the righthand half - 5 of Figure 1 being a section on line B-B of Figure 2; Figure 2 is a section on line C-C of the lefthand. half of Figure 4; Figure 3 is a cross-section through a diaphragm.; and Figure 4 shows a poppet, on a larger scale, for use with the diaphragm on Figure 3.

Tn general, the pump shown in Figure 1 possesses the same features as the pump disclosed in.

O.K. Patent Specification No. 1,503,122, parts which are particularly relevant to the present application will be described in detail.

The pump housing 4 contains two diaphragms 2 each contained in a chamber 3· Above each diaphragm 2 there is a space 3a for receiving hydraulic fluid, and below each diaphragm there is a space 3b ior receiving fluid to be pumped. The hydraulic fluid, which flattens the diaphragm to produce a pumping movement, enters the chamber 3 through a passage 4 from a piston unit 5 · The lower end of the passage 4 is flared outwardly at 6 to form a seat for a poppet 7- The poppet 7 is connected to the diaphragm 2 and will move up and down with the diaphragm as the diaphragm flexes.

A diaphragm 2 is shown on a larger scale in - 6 49005 Figure 3. It will he seen that the top face of the diaphragm has an undercut recess 8 for receiving the poppet 7· The poppet itself is shown on a larger scale in Figure 4, and it will he seen that this has a flange 9 which is received in the recess 8. No additional fixing means are required. The flange 9 is retained in place hy the lips of the undercut recess 8.

The edges of the diaphragm 2 have a right circular surface 10, and top and hottom flat annular surfaces 11 and 12. As shown in the righthand half of Figure 3, the diaphragm can easily he clamped in place hy three easily machined housing components. The central component 13 has a cylindrical bore, and the top and hottom components 14 and 15 just have flat surfaces which contact the flat surfaces 11 and 12. The components 14 and 15 are drawn together hy, for example, holts to provide an axial compression in the edge head of the diaphragm.

The poppet 7 has angled faces 16 which correspond to the angle of the outwardly flared passage portion 6. The angle of the faces 16 and the portion 6 may he, for example, 45° to the axis of the passage and the axis of the diaphragm movement.

The underside of the diaphragm has a step 17.

This is to prevent the area 18 of the diaphragm from - 7 49005 touching the metal plate 15 when the diaphragm is flattened.

Claims (8)

1. A high pressure diaphragm pump comprising a housing containing at least one self-restoring diaphragm, the or each diaphragm being arranged within 5 the housing so as to separate a space for receiving hydraulic fluid from a space for receiving fluid to be pumped, the space for receiving hydraulic fluid communicating with a hydraulic fluid supply via a passage, and the diaphragm carrying a poppet IO on its side facing the hydraulic fluid space, for closing said passage when the diaphragm reaches the end of its intake movement.

2. A pump as claimed in claim 1, wherein the passage enters the hydraulic fluid space via a flared 15 passage portion, and the poppet fits into the flared portion to close the passage. 5. A pump as claimed in claim 1 or claim 2, wherein the poppet is arranged to close the passage when there is still some hydraulic fluid 2o remaining within the hydraulic fluid space.

3. 4. A pump as claimed in any preceding claim, wherein the diaphragm is formed with an undercut recess which receives a flange of the poppet.

4. 5. A pump as claimed in any preceding claim, 25 wherein the passage for supplying hydraulic fluid - 9 49005 enters the hydraulic fluid space in the centre thereof, and the poppet is in the centre of the diaphragm.

5. 6. A pump as claimed in any preceding claim, wherein the or each diaphragm has a thickness to 5 diameter ratio of at least 1 to 5, and the peripheral edge of the or each diaphragm is a right cylindrical surface, and flat annular surfaces adjoin the cylindrical surface at the top and bottom of the peripheral edge; the diaphragm being mounted in the 10 housing within a cylindrical housing portion of diameter equal to or slightly less than the diameter of the right cylindrical surface, and being confined by surfaces exerting an axial compression on said top and bottom annular surfaces. 15

6. 7. A pump as claimed in any preceding claim, wherein the or each diaphragm has a step at the edge of its side which faces the space for receiving fluid to be pumped.

7.

8. A high pressure diaphragm pump substantially 2o as herein described with reference to the accompanying drawings.