EP3734066B1

EP3734066B1 - Electric axial membrane pump

Info

Publication number: EP3734066B1
Application number: EP19172663.7A
Authority: EP
Inventors: Johan Hendrik Schöppers
Original assignee: Mtp Met Plast Sp zoo
Current assignee: Mtp Met Plast Sp zoo
Priority date: 2019-05-03
Filing date: 2019-05-03
Publication date: 2021-09-01
Anticipated expiration: 2039-05-03
Also published as: PL3734066T3; ES2891984T3; EP3734066A1

Description

The invention relates to a membrane pump according to the preamble of claim 1.
Such a membrane pump is for example known from WO 99/25999 . Other membrane pumps are for example known from WO 2006055626 or Wikipedia (https://en.wikipedia.org/wiki/Diaphragm pump).
A membrane pump generates a pulsation in the fluid flow it pumps due to the reciprocating movement of the membranes. As a result the downstream fluid lines connected to the pump are subjected to stresses, high pressure and water hammer. These vibrations in the fluid lines cause furthermore noise, fatigue and wear.
Typically a long stroke is required with membrane pumps to obtain a substantial flow. This will require substantial dimensions of the membrane and the pump chambers, and thus of the pump housing.
It is an object of the invention to provide a membrane pump in which the above mentioned disadvantages are reduced or even removed.
This object is achieved with a membrane pump according to claim 1.
By having the main compartments adjacent to each other, the fluid flow can enter the housing centrally and divide to either the left pump chamber or the right pump chamber without much deviation. And the fluid can leave the main compartments and the housing centrally. The connecting channels between the inlet port and the inlet openings of the pump chambers, as well as the channels between the outlet port and the outlet openings can be short, such that the volume of fluid which has to be decelerated and accelerated when switching from one pump chamber to the other, can be kept small. As a result a more continuous flow is obtained and the pulsation in the downstream fluid lines is reduced, reducing stress, pressure peaks, noise, wear and so on.
By connecting the sub compartments of the two pump chambers via the equalizing channel, the movement of one membrane is assisted by the other membrane. When one membrane is compressing the main compartment, an under pressure will be generated in the corresponding sub compartment. However, the other membrane will be decompressing the corresponding main compartment, such that an overpressure will be generated in the sub compartment, which overpressure can be equalized with the underpressure in the other sub compartment.
This equalizing of pressure in the sub compartments will allow for a more free movement of the membranes, such that less energy is lost, making the membrane pump more effective.
In a preferred embodiment of the pump according to the invention, the driving means comprise:

an electric motor with a driven shaft;
an excenter mechanism arranged between the driven shaft and the connection rod for converting the rotational movement of the driven shaft into a reciprocating movement.

The use of an electric motor with an excenter mechanism allows for a high frequency of the stroke of the membranes. In combination with the main compartments being arranged adjacent to each other, which reduces the volume of fluid, which has to be decelerated and accelerated, a faster movement of the membranes is possible, which generates a high flow with reduced pulsation. Especially, a high frequency pulsation will have a smaller impact on the fluid lines than a low frequency pulsation.
In a further preferred embodiment of the membrane pump according to the invention, the excenter mechanism is a Scotch yoke mechanism.
A Scotch yoke, which is also known as a slotted link mechanism, is a reciprocating motion mechanism, converting the linear motion of a slider into rotational motion, or vice versa. The piston or other reciprocating part is directly coupled to a sliding yoke with a slot that engages a pin on the rotating part. The location of the piston versus time is a sine wave of constant amplitude, and constant frequency given a constant rotational speed.
The sine wave motion of the Scotch yoke mechanism causes a fluent acceleration and deceleration of the fluid volume within the membrane pump, such that pulsations are further reduced.
Preferably, the stroke length of the reciprocating movement is less than 20mm, preferably less than 12mm.
Furthermore preferred is that the rotational speed of the drive shaft is more than 250 revolutions per minute, preferably more than 295 revolutions per minute.
Especially the Scotch yoke mechanism is quite suitable for high speed driving by an electric motor. Due to the high frequency or revolutions per minute, the stroke can be small, while still generating a substantial fluid flow by the membrane pump according to the invention. The small stroke further allows for the dimensions of the housing to be relative small.
In yet another embodiment of the membrane pump according to the invention the one way valves arranged in the inlet openings and the outlet openings are flat check valves having a resilient flap closing off the respective opening.
The flat check valves allow for the distance between the two pump chambers to be reduced. The flat check valves will require little space, such that a higher rate of the space of the pump chamber can effectively be used for the movement of the membrane. The amount of fluid, present in connecting channels and the main compartment, at the end of a compression stroke of the membrane is reduced and accordingly less fluid needs to be decelerated and accelerated at each stroke of the membranes.
In another embodiment of the membrane pump according to the invention the inlet port and outlet port are arranged in an axial plane positioned between the two pump chambers.
Preferably, the main axis of the inlet port and main axis of the outlet port are coaxial.
This allows for the membrane pump to be arranged in a straight fluid line, such that no energy is lost by urging the fluid through bends of the fluid line, which would otherwise be necessary to connect the membrane pump in a fluid line.
In still a further embodiment of the membrane pump according to the invention the membranes are substantially cup-shaped.
Preferably, the walls of the sub compartments are cup-shaped and correspond to the cup-shaped membranes, such that in one end position of the reciprocal movement, the membrane is in substantial full contact with the cup-shaped walls of the sub compartments.
The cup-shape of the membranes allow for substantial flexibility to move the membrane from one axial end position to the other axial end position. Having the walls of the sub compartments corresponding to the cup-shape of the membranes a full stroke of the membrane will displace a maximal amount of fluid compared to the volume of the pump chamber, ensuring that the stroke volume of a membrane is optimized compared to the volume of the pump chamber.
These and other features will be elucidated in conjunction with the accompanying drawings.
Figure 1 shows an exploded view of an embodiment of the membrane pump 1 according to the invention.
Figures 2A and 2B show perspective views of the Scotch yoke mechanism of the pump of figure 1.
Figure 3 shows a cross sectional view of the inlet port and outlet port of the pump of figure 1.
Figures 4A and 4B shows schematic cross sectional views of the pump of figure 1 in two positions.
Figure 1 shows an exploded view of an embodiment of a membrane pump 1 according to the invention. The pump 1 has a housing consisting out of a number of housing parts 2, 3, 4, 5, which are typically bolted together. The housing parts 2, 3, 4, 5 allow for an easy disassembly, when the pump 1 requires maintenance.
An inlet port 6 and an outlet port 7 are arranged between the housing parts 3 and 4 and connect to inlet openings 8 and outlet openings 9.
Furthermore, a first membrane 10 is arranged between the housing parts 2 and 3, while a second membrane 11 is arranged between the housing parts 4 and 5. The first membrane 10 and the second membrane 11 are connected via a connection rod 12.
The membranes 10, 11 are reciprocatingly moved by an electric motor 13, which drives a Scotch yoke mechanism 14, which is coupled via a rod 15 to the membranes 10, 11.
Figure 2A and 2B show perspective views of the Scotch yoke mechanism 14. A drive shaft 16 is provided with a disc 17 on which an excentric stub 18 is provided. A bearing 19 is arranged on the stub 18 and is positioned within a body 20 provided with a slot 21. The body 20 is guided along two guides 22 and is coupled to the rod 15.
When the drive shaft 16 is driven by the electric motor 13, the excentric stub 18 will cause the bearing 19 to slide along the slot 21 and move the body 20 reciprocatingly along the two guides 22. This reciprocating movement is transferred via the rod 15 to the membranes 10, 11.
Figure 3 shows the inlet port 6 and the outlet port 7 in cross sectional view. The inlet port 6 connects via a Y-shaped channel 24 to the inlet openings 8, which are provided with flat check valves 23. The outlet port 7 is connected via a channel 25 to the outlet openings 9, which are provided with flat check valves 26.
Figure 4A shows a schematic cross-section of the pump 1 wherein the Scotch yoke mechanism 14 has pushed the rod 15 to the right.
The membrane 10 is arranged in a left pump chamber 30, 31 dividing said chamber into a main compartment 30 and a sub compartment 31. The membrane 11 is arranged in a right pump chamber 32, 33 dividing said chamber into a main compartment 32 and a sub compartment 33. Both sub compartments 31, 33 are in fluid connection with each other via an equalizing channel 34.
In the position shown in figure 4A, the rod 15 is driven to the right, such that the membrane 10 is compressing the main compartment 30 and the membrane 11 is decompressing the main compartment 32. As a result fluid F will flow via the inlet port 6 and the inflow opening 8 into the main compartment 32 of the right pump chamber 32, 33. Fluid F present in the left pump chamber 30, 31 is pressed via the outlet opening 9 out of the outlet port 7.
In the position shown in figure 4B, the rod 15 is driven to the left, such that the membrane 10 is decompressing the main compartment 30 sucking in fluid F via the inflow opening 8, while the membrane 11 is expelling the fluid F via the outlet opening 9 out through the outlet port 7.
Due to the relative small size of the channels 24, 25 a high stroke frequency can be used and pulsation disadvantages as known from the prior art are decreased.

Claims

Membrane pump (1) comprising:
- a housing (2, 3, 4, 5) having, along a main axis, two coaxial arranged pump chambers (30, 31, 32, 33) in which each a flexible membrane (10, 11) is arranged perpendicular to the main axis, which membranes (10, 11) are parallel to each other and divide each pumping chamber (30, 31, 32, 33) into a main compartment (30, 32) and a sub compartment (31, 33);

- wherein each main compartment (30, 32) has at least one inlet opening (8) and one outlet opening (9) and wherein one way valves (23, 26) are arranged in each inlet opening (8) and each outlet opening (9);

- an inlet port (6) arranged in the housing (2, 3, 4, 5) and in fluid connection with the inlet openings (8);

- an outlet port (7) arranged in the housing (2, 3, 4, 5) and in fluid connection with the outlet openings (9);

- a connection rod (12) extending coaxially through the housing (2, 3, 4, 5), wherein each end of the rod (12) is attached to a membrane (10, 11);

- driving means (15) coupled to the connection rod (12) for reciprocating driving of the connection rod (12) in axial direction,whereinthe two main compartments (30, 32) of the pump chambers (30, 31, 32, 33) are adjacent to each other and the two sub compartments (31, 33) of the pump chambers (30, 31, 32, 33) are distal from each other,
characterized in that
an equalizing channel (34) is arranged in the housing (2, 3, 4, 5), which equalizing channel (34) connects the sub compartments (31, 33) of the two pump chambers (30, 31, 32, 33) for equalizing pressure.
Membrane pump (1) according to claim 1, wherein the driving means comprise:
- an electric motor with a driven shaft (16);

- an excenter mechanism (14) arranged between the driven shaft (16) and the connection rod (15) for converting the rotational movement of the driven shaft (16) into a reciprocating movement.
Membrane pump (1) according to claim 2, wherein the excenter mechanism (14) is a Scotch yoke mechanism.
Membrane pump (1) according to claim 3, wherein the stroke length of the reciprocating movement is less than 20mm, preferably less than 12mm.
Membrane pump (1) according to claim 3 or 4, wherein the rotational speed of the driven shaft (16) is more than 250 revolutions per minute, preferably more than 295 revolutions per minute.
Membrane pump (1) according to any of the preceding claims, wherein the one way valves (23, 26) arranged in the inlet openings (8) and the outlet openings (9) are flat check valves having a resilient flap closing off the respective opening (8, 9).
Membrane pump (1) according to any of the preceding claims, wherein the inlet port (6) and outlet port (7) are arranged in an axial plane positioned between the two pump chambers (30, 31, 32, 33).
Membrane pump (1) according to claim 7, wherein the main axis of the inlet port (6) and main axis of the outlet port (7) are coaxial.
Membrane pump (1) according to any of the preceding claims, wherein the membranes (10, 11) are substantially cup-shaped.
Membrane pump (1) according to claim 9, wherein the walls of the sub compartments (31, 33) are cup-shaped and correspond to the cup-shaped membranes (10, 11), such that in one end position of the reciprocal movement, the membrane (10, 11) is in substantial full contact with the cup-shaped walls of the sub compartments (31, 33).