Classifications

• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
  • F04B—POSITIVE-DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS
  • F04B43/00—Machines, pumps, or pumping installations having flexible working members
  • F04B43/0009—Special features
  • F04B43/0054—Special features particularities of the flexible members
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
  • F04B—POSITIVE-DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS
  • F04B43/00—Machines, pumps, or pumping installations having flexible working members
  • F04B43/0009—Special features
  • F04B43/0081—Special features systems, control, safety measures
  • F04B43/009—Special features systems, control, safety measures leakage control; pump systems with two flexible members; between the actuating element and the pumped fluid
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
  • F04B—POSITIVE-DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS
  • F04B43/00—Machines, pumps, or pumping installations having flexible working members
  • F04B43/02—Machines, pumps, or pumping installations having flexible working members having plate-like flexible members, e.g. diaphragms
  • F04B43/06—Pumps having fluid drive
  • F04B43/073—Pumps having fluid drive the actuating fluid being controlled by at least one valve
  • F04B43/0736—Pumps having fluid drive the actuating fluid being controlled by at least one valve with two or more pumping chambers in parallel

Definitions

• This invention relates to positive displacement airpowered diaphragm pumps,.
• Such pumps apply compressed air to one side of a diaphragm so as to transmit the pressure of the air to fluid on the other side of the diaphragm.
• Diaphragm movement effects positive displacement of the fluid at a pressure substantially equal to the pressure of the motive air.
• the pump is to be self-priming means must be provided for drawing the diaphragm back for a repeat pumping stroke. This drawing back movement of the diaphragm is referred to herein as the return stroke, and must be capable of drawing a substantial head of fluid from a source to the pump.
• One prior proposed air powered diaphragm pump comprises two diaphragms each associated with its own pumping chamber for fluid to be pumped and its own air chamber for compressed air.
• the diaphragms are interconnected by a shaft passing through the two air chambers, and valving ensures that compressed air is supplied to and exhausted from the two air chambers alternately.
• This diaphragm movement is transmitted via the shaft to the other diaphragm so as to cause it to effect its return stroke and draw more fluid from the source.
• Such a pump is referred to herein for convenience as a back-to-back pump, as it consists of two single acting diaphragm pumps mounted back to back and having the diaphragms interconnected so as to move only in unison. It is essentially a double-acting pump, as the diaphragms effect their pumping strokes alternately. It has, however, certain limitations and disadvantages as will be apparent below.
• This invention comprises a positive displacement diaphragm pump having an air chamber, a pumping chamber for fluid to be pumped, and a composite diaphragm between the air chamber and the pumping chamber, characterised in that the composite diaphragm comprises a first membrane communicating with the air chamber, a second membrane of smaller area than the first communicating with the pumping chamber, and a further air chamber between, and defined by, the first and second membranes, and means is provided for alternately supplying compressed air to the air chamber to effect a pumping stroke of the composite diaphragm and exhausting the air chamber-while supplying compressed air to the further air chamber to effecta return stroke of the composite diaphragm.
• the composite diaphragm of the pump of this invention may be considered self-erecting in that it is air pressure between the two membranes that effects the return stroke rather than a shaft passing through two air chambers as in the conventional back-to-back pumps.
• the area difference between the two membranes causes return stroke movement, and suitable design and choice of the membrane areas enables a desired head of fluid to be drawn on the return stroke of the diaphragm.
• the composite diaphragm may comprise a pair of spaced diaphragms linked at their mid points by a connecting shaft or plate so as to move only in unison.
• a connecting plate used for such a purpose conveniently serves also as a backing plate for the centre plate of each diaphragm.
• the composite diaphragm may comprise first and second spaced membranes which are joined over the whole of their facing surfaces by a non-cellular porous spongy material.
• This spongy material should be air-permeable so that although it bonds the membranes to one another to move only in unison, it also defines the further air chamber therebetween.
• the materials for the two membranes may be the same or different.
• the first membrane is in contact only with air on both sides thereof, and if desired a lower standard material may be used than for the second membrane one side of which contacts the fluid to be pumped.
• a rubberized asbestos or rubberized canvas diaphragm may be used as the first membrane while a more durable diaphragm, such as one made from a Viton (Trade Mark), neoprene, polyurethane, butyl or nitrile high resistant rubber , may be used as the second membrane.
• Viton Trade Mark
• neoprene polyurethane
• butyl or nitrile high resistant rubber may be used as the second membrane.
• the choice of material for the second membrane is related to the nature of the fluids to be pumped.
• a pump according to this invention has all the versatility of conventional diaphragm pumps as regards the range of fluids that can be pumped. It can cope with liquids of high viscosity, up to and including pastes, and with slurries of even quite large particles. Because there are no pistons, shafts, sliding seals or rotating parts, the pump is particularly dependable in use. Conventional nonreturn valves may be used in the fluid supply and delivery lines.
• the means for controlling the air supply to the air chamber and the further air chamber may be any conventional air valve, such as a spool or shuttle valve.
• the air valve may be controlled by mechanical means, such as a probe extending into the air chamber and responsive to the position of the composite diaphragm.
• it may be controlled by air logic, utilizing small changes in the air pressure at a pilot pressure port to determine when the composite diaphragm is at the ends of its stroke; or it may operate on a time sequence; or it may be responsive to an operator's control.
• the pump of this invention has so far been described in terms of a single acting pump which delivers a pulsating output pressure from alternate pumping and return strokes of the diaphragm. If desired two such pumps can be used in concert, fed by air from the same air valve effective to cause the two composite diaphragms to produce their pumping strokes alternately.
• the physical arrangement of the two pumps is not however limited to back-to-back as in the prior art pumps, as there is no mechanical connection between the composite diaphragms of the two pumps.
• Figure 1 is an axial section through a pump according to this invention with the composite diaphragm at the beginning of its working stroke;
• Figure 2 is an axial section through the pump of Figure 1, with the composite diaphragm at the end of its working stroke and about to begin its return stroke;
• Figure 3 is a schematic diagram showing how two pumps according to Figure 1 can be connected together to provide a substantially constant pressure output.
• the pump comprises a housing formed from housing halves 10 and 12 between which is a spacer ring 14. Clamped between the housing half 10 and the spacer ring 14 is a first diaphragm 16, and clamped between the spacer ring 14 and the housing half 12 is a second diaphragm 18. The whole is clamped together by means of bolts (not shown) so as to provide a reliably fluid tight seal around the edges of the two diaphragms.
• the first diaphragm 16 is provided with a cover plate 20 and the second diaphragm 18 is provided with a cover plate 22.
• Each of these cover plates 20 and 22 is fastened securely to a spacer disc 24 by means of bolts (not shown) so that the two diaphragms are permitted to move only in unison.
• the two diaphragms 16 and 18, their cover plates 20 and 22 and the spacer disc 24 thus form a composite diaphragm that is movable between the two positions shown in Figures 1 and 2.
• the first diaphragm 16 and its cover plate 20 are larger in diameter than the second diaphragm 18 and its cover plate 22.
• an air chamber 26 Between the first diaphragm 16 and the housing half 10 is formed an air chamber 26, and between the first and second diaphragms 16 and 18 is formed a further air chamber 28. Between the second diaphragm 18 and the housing half 12 is formed a pumping chamber 30 for fluid to be pumped.
• the supply of compressed air to the air chamber 26 and the further air chamber 28 is controlled by an air control valve 32 which alternately directs the compressed air to an air port 34 leading to the air chamber 26 and to an air port 36 leading to the further air chamber 28.
• the air port 36 is provided as a radial bore through the spacer ring 14. Air is supplied to the air control valve from any suitable compressed air source, through a line 38.
• a fluid valve assembly 40 Communicating with the pumping chamber 30 is a fluid valve assembly 40, which comprises a pair of one-way valves.
• the valves permit fluid flow in a line 42 from a fluid source only in a direction towards the pumping chamber, and permit fluid flow in a delivery line 44 only in a direction away from the pumping chamber.
• the air control valve 32 directs compressed; air from the supply line 38 to the air chamber 26 through the air port 34, and exhausts air from the further air chamber 28 via the air port 36.
• the air pressure in the air chamber 26 acts over the whole of the area of the first diaphragm so as to move the diaphragm from the position of Figure 1 to that of Figure 2. This has the effect of expelling the fluid from pumping chamber 30 via the fluid delivery line 44 at a maximum discharge pressure that is directionally proportional to the pressure of the compressed air.
• the composite diaphragm is returned to the position of Figure 1 by me-ans of the air control valve 32 which reverses its porting so as to supply compressed air from the supply line 38 through the air port 36 into the further air chamber 28, while exhausting air from the air chamber 26.
• the working area of the first diaphragm 16 forming one boundary of the further air chamber 28 is greater than the corresponding working area of the second diaphragm 18. A net upward force is therefore imparted to the composite diaphragm, with the effect that it goes on its return stroke to the position of Figure 1.
• the force imparted to the composite diaphragm on its return stroke by the compressed air in the further air chamber 28 is dependent on the pressure of the air from the supply and the difference in working areas of the two diaphragms. It is however perfectly feasible to design a pump according to this invention which can draw fluid, on the return stroke, at the theoretical maximum head of 34 feet for water while still maintaining substantial reserves of energy, to move the composite diaphragm at any maximum speed that can be desired in practice.
• FIG. 1 and 2 do not illustrate any particular means for governing the operation of the air control valve 32, it will be understood that this va lve could be actuated by a timer mechanism, or by a sensor mechanism or by a combination of both .
• the timer mechanism would simply reverse the actuation of the air control valve repeatedly after successive time intervals .
• a sensor mechanism would be responsive to a pilot pressure, representative of the pressure in the air chamber 26, or would be responsive to the position of the cover plate 20.
• a push rod may extend downwardly through the air port 34 so as to contact the cover plate 20.
• the push rod would cause reversal of the actuation of the air control va lve so as to supply compressed air to the air chamber 26 and exhaust the further air chamber 28, to drive the diaphragm on its pumping stroke .
• Further reversal of the actuation of the air control valve at the completion of the pumping stroke could then be achieved by biassing the push rod downwardly against the cover plate 20, for example by means of a spring or air pressure, so that the air control valve can sense the completion of the pumping stroke .
• compressed air from the air line 38 could be supplied at all times to the further air chamber 28 through the air port 36.
• FIG. 3 there is shown a combination of two pumps according to Figure 1, sharing the same air control valve 32.
• the further air chambers 28 of the two pumps are both supplied at all times with compressed air from the air supply line 38 and the air control valve 32 applies the same compressed air alternately to the two air chambers 26.
• the air chamber 26 of the other pump is opened to exhaust.
• the result is a double acting pump assembly, which delivers fluid at a substantially constant output pressure without the pulsating action of a single acting pump.

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• Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
• General Engineering & Computer Science (AREA)
• Reciprocating Pumps (AREA)

Priority Applications (1)

Applications Claiming Priority (2)

Publications (1)

Family

ID=10423332

Family Applications (1)

Country Status (6)

Cited By (1)

Families Citing this family (4)

Citations (11)

• 1978
  • 1978-10-11 JP JP50000279A patent/JPS54500006A/ja active Pending
  • 1978-10-11 GB GB7937001A patent/GB2036168B/en not_active Expired
  • 1978-10-11 DE DE2857091A patent/DE2857091C1/de not_active Expired
  • 1978-10-11 WO PCT/GB1978/000021 patent/WO1979000197A1/en unknown
• 1979
  • 1979-04-24 EP EP78900152A patent/EP0007945A1/en not_active Withdrawn
  • 1979-11-09 SE SE7909301A patent/SE7909301L/sv unknown

Patent Citations (11)

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