U.S. patent application number 14/081919 was filed with the patent office on 2014-05-15 for magnetic circuit.
The applicant listed for this patent is Mindray Medical Sweden AB. Invention is credited to Torbjorn Boxell, Joakim Gabrielsson, Johan Werner.
Application Number | 20140134019 14/081919 |
Document ID | / |
Family ID | 50681866 |
Filed Date | 2014-05-15 |
United States Patent
Application |
20140134019 |
Kind Code |
A1 |
Werner; Johan ; et
al. |
May 15, 2014 |
MAGNETIC CIRCUIT
Abstract
A magnetic circuit for a voice coil, comprising, a magnet cup
with a one sided open cylindrical shape with a base. The magnetic
circuit further includes a conical magnet with a side including a
partial conical shape. The magnetic circuit includes a pole shoe
which has a side with a recessed conical shape corresponding to the
conical shape of said magnet. The magnet cup, the conical magnet
and the pole shoe are stacked so that the conical magnet is
centrally arranged on the base inside said magnet cup, the pole
shoe is arranged on the conical magnet so that the side with a
recessed conical shape of the pole shoe is in contact with the side
with a conical shape of the conical magnet, such that an air gap is
obtained between an inner wall surface of the magnet cup and the
stacked conical magnet and the pole shoe.
Inventors: |
Werner; Johan; (Skogsas,
SE) ; Gabrielsson; Joakim; (Taby, SE) ;
Boxell; Torbjorn; (Alvsjo, SE) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Mindray Medical Sweden AB |
Sundbyberg |
|
SE |
|
|
Family ID: |
50681866 |
Appl. No.: |
14/081919 |
Filed: |
November 15, 2013 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
61727012 |
Nov 15, 2012 |
|
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|
61726962 |
Nov 15, 2012 |
|
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61726965 |
Nov 15, 2012 |
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Current U.S.
Class: |
417/413.1 ;
310/12.16 |
Current CPC
Class: |
Y10T 29/49236 20150115;
F04B 43/0063 20130101; F04B 45/047 20130101; H02K 41/0356 20130101;
F04B 43/04 20130101 |
Class at
Publication: |
417/413.1 ;
310/12.16 |
International
Class: |
F04B 45/047 20060101
F04B045/047; H02K 1/34 20060101 H02K001/34 |
Foreign Application Data
Date |
Code |
Application Number |
Nov 15, 2012 |
EP |
12192847.7 |
Nov 15, 2012 |
EP |
12192859.2 |
Nov 15, 2012 |
EP |
12192889.9 |
Claims
1. A magnetic circuit for a voice coil, comprising: a magnet cup
including a one-sided open cylindrical shape with a base, said base
including an inner surface; a conical magnet including a least one
side with an at least partial conical shape; and a pole shoe
including a side with a recessed conical shape corresponding to
said conical shape of said conical magnet, wherein said magnet cup,
said conical magnet, and said pole shoe are stacked so that said
conical magnet is centrally arranged on said base inside said
magnet cup, said pole shoe is arranged on said conical magnet so
that said side with a recessed conical shape of said pole shoe is
in contact with said side with a conical shape of said conical
magnet, and said stack is arranged such that an air gap is obtained
between an inner wall surface of said magnet cup and said stacked
conical magnet and said pole shoe.
2. The magnetic circuit of claim 1, wherein said base has an inner
surface area with a partially conical shape protruding inward,
wherein said magnet cup and said conical shape are at a central
portion of said base of said cylindrical shape, and wherein said
conical magnet has a second side with a recessed conical shape
corresponding to said conical shape of said inner surface area of
said base.
3. The magnetic circuit of claim 2, wherein the base has an outer
surface with a recessed conical shape.
4. The magnetic circuit of claim 1, wherein a coil is arranged in
said air gap.
5. The magnetic circuit of claim 4, wherein said coil is entwined
by self-adhesive lining.
6. The magnetic circuit according to claim 1, wherein said stack
has a bore going at least partially through and said bore is
arranged at the centre of said stack.
7. The magnetic circuit of claim 6, wherein a shaft is arranged in
said bore, and said shaft is connected to said coil.
8. The magnetic circuit of claim 7, wherein said shaft is linearly
movable in a reciprocating stroke motion.
9. The magnetic circuit according to claim 1, wherein the angles of
said conical shapes span the range 10 to 45 degrees.
10. The magnetic circuit according to claim 1, wherein said conical
magnet is made of at least one of neodymium, samarium-cobolt, and
alnico.
11. The magnetic circuit according to claim 1, wherein said pole
shoe and said magnetic cup are made of ferromagnetic metals or
alloys.
12. A membrane pump, comprising: a magnetic circuit for a voice
coil, including: a magnet cup including a one-sided open
cylindrical shape with a base, said base including an inner
surface; a conical magnet including a least one side with an at
least partial conical shape; and a pole shoe including a side with
a recessed conical shape corresponding to said conical shape of
said conical magnet, wherein said magnet cup, said conical magnet,
and said pole shoe are stacked so that said conical magnet is
centrally arranged on said base inside said magnet cup, said pole
shoe is arranged on said conical magnet so that said side with a
recessed conical shape of said pole shoe is in contact with said
side with a conical shape of said conical magnet, and said stack is
arranged such that an air gap is obtained between an inner wall
surface of said magnet cup and said stacked conical magnet and said
pole shoe; a pump housing comprising a chamber with an open end;
and a membrane element including a first area arranged to cover
said open end of said chamber, wherein said magnetic circuit is
arranged and adapted to transfer a force by a stroke motion on said
membrane.
13. The membrane pump according to claim 12, wherein said membrane
element comprises a central section with a second area surrounded
by a periphery section, wherein said central section is thicker
than said periphery section, and wherein said second area of said
central section is smaller than a third area of said open end of
said chamber of which said central section is arranged over.
14. The membrane pump according to claim 13, wherein said chamber
comprises a bevelled inner wall; and wherein said central section
of said membrane element is centrally arranged over said open end,
and said first area of said membrane element is larger than said
third area.
15. The membrane pump according to claim 12, wherein said pump
housing has an enlarged surface surrounding said open end of said
chamber with an area having at least the same size as said first
area of said membrane element.
16. The pump according to claim 15, wherein said membrane element
is slidably clamped between said elongated surface of said pump
housing and a second member of said pump housing.
17. A method for assembling a magnetic circuit for a voice coil,
comprising: providing a magnetic cup with a one-sided open
cylindrical shape with a base, said base including an inner
surface; providing a conical magnet including at least one side
with an at least partial conical shape; providing a pole shoe
including a side with a recessed conical shape corresponding to
said conical shape of said conical magnet; stacking said magnet
cup, said conical magnet and said pole shoe so that said conical
magnet is centrally arranged on said base inside said magnet cup,
said pole shoe is arranged on the conical magnet so that said side
with a recessed conical shape of said pole shoe is in contact with
said side with a conical shape of said conical magnet, and said
stack is arranged such that an air gap is obtained between an inner
wall surface of said magnet cup and said stacked conical magnet and
said pole shoe, wherein said magnet cup, said conical magnet and
said pole shoe are configured to magnetically self-align when
stacked.
Description
RELATED APPLICATIONS
[0001] The present application claims the benefit under 35 U.S.C.
.sctn.119(e) of U.S. Provisional Patent Application 61/726,962
filed Nov. 15, 2012 titled "PROGRESSIVE PUMP FORCE REGULATION,"
U.S. Provisional Patent Application 61/726,965 filed Nov. 15, 2012
titled "EXTENDED ELASTICITY OF PUMP MEMBRANE WITH CONSERVED PUMP
FORCE," and U.S. Provisional Patent Application 61/727,012 filed
Nov. 15, 2012 titled "Magnetic Circuit," each of which applications
is hereby incorporated herein by reference in their entirety.
[0002] The present application also claims a priority benefit
claims the benefit under 35 U.S.C. .sctn.119 of European Patent
Application 12192847.7 filed Nov. 15, 2012 titled "PROGRESSIVE PUMP
FORCE REGULATION," European Patent Application 12192859.2 filed
Nov. 15, 2012 titled "EXTENDED ELASTICITY OF PUMP MEMBRANE WITH
CONSERVED PUMP FORCE," and European Patent Application 12192889.9
filed Nov. 15, 2012 titled "Magnetic Circuit," each of which
applications is hereby incorporated herein by reference in their
entirety.
[0003] It is appreciated that the embodiments disclosed in each of
the applications above may be combined in and/or utilized in
combination with one another. For instance, one or more of the
embodiments and/or one or more elements of embodiments described in
conjunction with the "PROGRESSIVE PUMP FORCE REGULATION"
application may be combined and/or used in combination with one or
more embodiments or elements of embodiments described in
conjunction with the "EXTENDED ELASTICITY OF PUMP MEMBRANE WITH
CONSERVED PUMP FORCE" application and/or the "Magnetic Circuit"
application.
BACKGROUND
[0004] 1. Field of the Disclosure
[0005] This disclosure pertains in general to voice coil. More
particularly the disclosure relates to voice coils for driving
membrane pumps used, for example, as sampling pumps in devices for
patient monitoring, breath monitoring, anaesthesia monitoring,
especially for medical ventilation monitoring and gas analyzers for
monitoring gas composition in patient's breathing.
[0006] 2. Description of the Related Art
[0007] The common way of designing a magnetic circuit, such as for
a voice coils, is to make the magnet strictly cylindrical and if a
pole shoe is used it is normally strictly cylindrical too. The pole
shoe is used to collect the magnetic flux and redirect it to a pure
radial direction. The density of the magnetic flux inside the steel
parts (magnet cup and pole shoe) is depending of the section area
of the parts. If it is too concentrated, the steel will be
saturated and not able to conduct any more flux which leads to both
leakage of magnetic flux (i.e. immediate magnetic material will be
attracted) and limit the circuit's capacity. The cylindrical design
of the magnet cup is also limiting the voice coil to have a mount
of its free shaft end outside this cylindrical outer shape.
[0008] Hence, a new improved design of a magnetic circuit with
better directing capability of the flux would be advantageous,
especially if the same magnetic circuit has a small volume.
SUMMARY
[0009] Accordingly, embodiments of the present disclosure
preferably seek to mitigate, alleviate or eliminate one or more
deficiencies, disadvantages or issues in the art, such as the
above-identified, singly or in any combination by providing a
device, system or method according to the appended patent claims
for providing an improved magnetic circuit, such as in voice coil
devices. These voice coils may be used in membrane pumps for
patient monitoring, breath monitoring, anaesthesia monitoring,
especially for medical ventilation monitoring and gas analyzers for
monitoring gas composition in patient's breathing.
[0010] Disclosed herein are device, system and methods for
providing the improved magnetic circuit.
[0011] According to one aspect of the disclosure, a magnetic
circuit for a voice coil includes a magnet cup which has a one
sided open cylindrical shape with a base, the base has an inner
surface, a conical magnet which has a side with an at least partial
conical shape, and a pole shoe which has a side with a recessed
conical shape corresponding to the conical shape of the conical
magnet, is disclosed. The magnet cup, the conical magnet and the
pole shoe are stacked so that the conical magnet is centrally
arranged on the base inside said magnet cup, then the pole shoe is
arranged on the conical magnet so that the side with a recessed
conical shape of said pole shoe is in contact with the side with a
conical shape of said conical magnet. The stack is arranged such
that an air gap is obtained between an inner wall surface of the
magnet cup and the stacked conical magnet and said pole shoe.
[0012] The conical shape allows for a better distribution of
magnetic flux inside the pole shoe. The design also improves the
assembly of the magnetic circuit, as the conical shape allows for a
self-alignment between the conically shaped parts.
[0013] In some examples of the disclosure, the base has an inner
surface area with a partially conical shape protruding inward the
magnet cup and the conical shape is at a central portion of the
base of the cylindrical shape. Further, the conical magnet has a
second side with a recessed conical shape corresponding to the
conical shape of the inner surface area of base.
[0014] By having a conical shaped interface between the conical
magnet and the inner surface of the magnet cup improves the
distribution of the magnetic flux in the magnetic circuits.
[0015] Even further, by having all three parts conically shaped
improves the self-alignment properties of the stack even
further.
[0016] In some examples of the disclosure the base has an outer
surface with a recessed conical shape.
[0017] Moreover, the conical shape of the base makes it possible to
have a recessed outer surface of the base which creates a space
which may be used to add a support for a free shaft end without
adding any volume outside the cylindrical volume. Hence the voice
coil may be smaller in size.
[0018] An airgap may be obtained between an inner surface area of
the cylindrical shape of the magnet cup and the outer surface of
the stacked conical magnet and the pole shoe. In this airgap a coil
may be arranged.
[0019] In some examples is the coil entwined by self-adhesive
lining. This design may take advantage of the limit space of the
airgap. Hence smaller voice coils are possible to design.
[0020] In some further examples, a bore may go at least partially
through the height of the stack. The bore is preferably arranged at
the centre of the stack. In this bore a shaft may be arranged. The
shaft may be connected to the coil so that when the coil moved the
shaft will move. The motion of the shaft is a linear reciprocating
stroke motion.
[0021] In some examples of the disclosure, the angle of the conical
shapes spans the range 10 to 45 degrees.
[0022] Some materials of which the conical magnet may be made of
are neodymium, samarium-cobalt, or alnico.
[0023] The pole shoe and the magnetic cup may be made of
Ferromagnetic metals and/or alloys.
[0024] According to another aspect of the disclosure, a membrane
pump is disclosed. The membrane pump comprises a magnetic circuit
in accordance with the disclosure herein, a pump housing with a
chamber having an open end. The membrane pump also includes a
membrane element having a first area arranged to cover the open end
of the chamber. The magnetic circuit is arranged and adapted to
transfer a force by a stroke motion on the membrane.
[0025] In some examples of the membrane pump, the membrane element
comprises a central section with a second area surrounded by a
periphery section. The central section is thicker than the
periphery section, and the second area of the central section is
smaller than a third area of the open end of the chamber of which
the central section is arranged over.
[0026] The advantages with this disclosed configuration is that it
prevents the stroke from hitting the bottom of the chamber since a
pump stroke is decelerated in a progressive way which not only
makes the stop silent but also reduces the mechanical vibrations
and keep them to a minimum. Further, the deceleration reduces the
effective pump area of the membrane closer to the end of a stroke.
Since the force of the stroke is constant, the pump becomes
stronger closer to the end of the stroke.
[0027] In some further examples, the chamber may have bevelled
inner walls. The central section of the membrane element is
centrally arranged over the open end and the first area of the
membrane element is larger than the third area of the open end.
[0028] Also, in some examples the pump housing may have an enlarged
surface surrounding the open end of the chamber with a total area
having at least the same size as the membrane element.
[0029] In some further examples of the disclosure, the membrane
element is slidably clamped between the elongated surface of the
pump housing and a second member of the pump housing.
[0030] The advantages with this configuration are that by holding a
membrane element slidably fixed at a larger diameter than the
actual working diameter (area) is that the membrane if free to move
radial and stretch. Hence a longer pump stroke may be achieved
(i.e. more volume can be pumped per stroke). Also a longer life of
the membrane due to lower fatigue stress levels and more effective
use of the available pump force may be obtained.
[0031] According to a further aspect of the disclosure, a method
for assembling part to a magnetic circuit is disclosed. The method
comprises, utilizing a conical design of the parts and a magnetic
force of the magnetic circuit to allow different parts to
self-orient.
[0032] The conical shape allows for a much easier assembly
operation since the shape makes the parts self-orienting.
[0033] In this disclosure the word "conical" is defined both as
strictly conical but also as a truncated cone.
[0034] It should be emphasized that the term "comprises/comprising"
when used in this specification is taken to specify the presence of
stated features, integers, steps or components but does not
preclude the presence or addition of one or more other features,
integers, steps, components or groups thereof.
BRIEF DESCRIPTION OF THE DRAWINGS
[0035] These and other aspects, features and advantages of which
examples of the disclosure are capable of will be apparent and
elucidated from the following description of embodiments of the
present disclosure, reference being made to the accompanying
drawings, in which
[0036] FIGS. 1A and 1B are illustrating cross-sectional schematic
overviews of examples of a magnetic circuit;
[0037] FIGS. 2A and 2B are illustrating cross-sectional schematic
overviews of flux distribution in a prior art circuit and an
example of the disclosed circuit;
[0038] FIGS. 3A and B are illustrating cross-sectional schematic
overviews of simulated flux distribution in a prior art circuit and
an example of the disclosed circuit; and
[0039] FIG. 4 is illustrating a cross-sectional schematic overview
of a membrane pump.
DESCRIPTION OF EMBODIMENTS
[0040] Specific examples of the disclosure now will be described
with reference to the accompanying drawings. This disclosure may,
however, be embodied in many different forms and should not be
construed as limited to the embodiments set forth herein; rather,
these embodiments are provided so that this disclosure will be
thorough and complete, and will fully convey the scope of the
disclosure to those skilled in the art. The terminology used in the
detailed description of the embodiments illustrated in the
accompanying drawings is not intended to be limiting of the
disclosure. In the drawings, like numbers refer to like
elements.
[0041] The following description focuses on an embodiment of the
present disclosure applicable to a magnetic circuit and to a voice
coil. The voice coil is to be used as an actuator. For example, the
voice coil may be used as an actuator for a membrane pump, such as
a sampling pump in devices for patient monitoring, breath
monitoring, anaesthesia monitoring, especially medical ventilation
monitoring and gas analyzers for monitoring gas composition in
patient's breathing. However, it will be appreciated that the
description is not limited to this application but may be applied
to many other systems where a fluid pump is required.
[0042] FIG. 1A is a magnetic circuit 100. The magnetic circuit
comprises a magnet cup 7 which have a one sided open cylindrical
shape with a base. The base is partially conical and the cone is
directed inward the cylinder. The cone shape is located at a
central portion of the base of the cylinder. The magnetic circuit
100 also comprises a conical magnet 8 and a pole shoe 9. The pole
shoe 9 has one side which has a conical shape being directed
inwards. These three components are stacked so that the conical
magnet 8 is arranged on the base, inside the magnet cup 7. The pole
shoe 9 is then arranged on the conical magnet 8.
[0043] Additionally, when arranged in this fashion an airgap 11 is
obtained between an inner surface area 20 of the cylinder and one
side of the parts stacked inside the magnetic cup 7.
[0044] In this airgap, a coil (not seen in the figure) may be
arranged. In some examples of the magnetic circuit, the coil is
entwined by self-adhesive lining. This design may take advantage of
the limit space of the airgap. Hence a smaller design of the
magnetic circuit is possible.
[0045] Alternatively to the illustration in FIG. 1A, only the
interface between pole shoe 9 and the conical magnet 8 may be
conical.
[0046] By using a pole shoe 9 in the magnetic circuit 100 wherein
the pole shoe 9 having a recessed conical shape in contact with a
corresponding conical shape of an conical magnet, the magnetic flux
inside the conicla magnet 8 is purely axial. Thus all of the flux
is transferred into the pole shoe 9 and the magnet cup 7. Since the
flux inside the pole shoe 9 is redirected towards the magnetic cup
7 the flux density is lower closer to the cylindrical centre than
at the outer side. It is therefore an advantage to make the design
conical since this also allows for a larger sized magnet, if
desirable.
[0047] As illustrated in FIG. 1B the magnetic cup 7 does not need
to have a conical recess on an outer surface of the base.
[0048] On the other side, if also the magnets 8 other side (the one
facing the magnet cup 7) is made conical and the base of the cup
shape 7 too (like in FIG. 1), a small conical space is created
which is suited to host a good flexible support for the oscillating
free voice coil shaft without requiring any extra space for this
necessary feature.
[0049] Some examples of magnetic materials, from which the conical
magnet 8 may be made of, are neodymium, samarium-cobalt, or alnico.
The pole shoe 9 and the magnetic cup 7 may be made of ferromagnetic
metals and/or alloys.
[0050] Additionally, in some examples of the magnetic circuit 100
in FIGS. 1A and 1B, the angle 10 of the conical shapes span the
range from 10 to 45 degrees.
[0051] Additionally and/or alternatively if also the interface
between the conical magnet 8 and the inner surface of the base of
the magnetic cup is conical, such as illustrated in FIG. 1A and 1B,
the angle 15 may also be from 10 to 45 degrees.
[0052] The angles 10 and 15 may have the same gradient or the
angles 10 and 15 may have different gradients.
[0053] The thickness proportions of between different part such as
the wall of the magnetic cup 7 and the pole shoe 9 in regard to
magnetic flux, depends on the grad and strength of the magnet. But
it also depends on the function of the magnetic circuit and the
cylindrical section area.
[0054] In some examples of the magnetic circuit 100, the stack of
parts may have a bore 6 going at least partially through. The bore
6 is arranged at the centre of the stack. A shaft connected to the
coil in the airgap 11 may be arranged in the bore 6. When driving a
voltage or current through the coil shaft will move linear in a
reciprocating stroke motion. This can be utilised as a pump head to
exert a force on a membrane of a membrane pump.
[0055] Also, assembling a voice coil magnetic circuit requires much
carefulness. It is absolutely necessary to assemble the magnet and
the pole shoe concentric to make it work. This can be very tricky
since the magnet forces always pulls the magnet and pole shoe
towards the cylindrical wall of the magnet cup. By using the
conical design of the parts, the magnetic circuit becomes
self-oriented. The magnetic force will pull the conical parts
together at the centre of the cup as intended. Hence this effect
may be improved if all three parts have conical shapes.
[0056] FIGS. 2A and 2B are schematically illustrating the magnetic
flux distribution in a prior art (FIG. 2A) magnetic circuit 200 and
in an example of the disclosed (FIG. 2B) magnetic circuit 100.
[0057] FIGS. 3A and 3B are simulations to schematically illustrate
the magnetic flux distribution in a prior art (FIG. 3A) magnetic
circuit 200 and in an example of the disclosed (FIG. 3B) magnetic
circuit 100. The scales of the simulations are not the same so
FIGS. 3A and 3B are only used for the purpose of illustrating the
differences in magnetic flux distribution.
[0058] FIG. 4 illustrates a cross-sectional view of an example of a
membrane pump 300. The membrane pump 300 comprises a membrane
element 33 a pump housing 1, and optional second housing member 5
(e.g. membrane fixing plate) and a pump chamber 21. In this
example, the pump chamber 21 has bevelled walls for abutting an
area where the membrane element 33 becomes thicker. Hence
decelerate the pump stroke in a progressive way.
[0059] A portion of the membrane may be slidably clamped between
the second member 5 and the pump housing 1. This allows the
membrane to move radial and stretch when a force is applied.
[0060] The advantages with this configuration are that by holding a
membrane element slidably fixed at a larger diameter than the
actual working diameter (area), the membrane is free to move radial
and stretch. Hence a longer pump stroke may be achieved (i.e. more
volume can be pumped per stroke). Also, due to the radial movement,
the same pump volume can be maintained with less stretching which
will increase the life of the membrane due to lower fatigue stress
levels and more effective use of the available pump force may be
obtained.
[0061] Additionally and/or alternatively, by designing the edge of
the second pump housing member 5 (i.e. membrane fixing plate) to be
conical or with one or more radii positioned in the area where the
membrane element 32 becomes stiffer (thicker) it may also be
possible to decelerate the pump stroke in a progressive way. This
will make the stops, when the membrane element is in its turning
point silent and also reduces the mechanical vibrations due to the
progressive motion deceleration.
[0062] The pump further comprises a pump head 12. In this example,
the pump head 12 is abutting the central section of the membrane
element 33. Alternatively, in some examples, the pump head may be
mechanically attached to the top of central section, such as
inserted into the central section or a screw could be used to
secure them together. When using a pump head 12 abutting the top of
the central section an adhesive may be used between the top of the
central section and the abutting area of the pump head 12 to affix
the two members. Examples of adhesives may be, glue, sticky tape,
etc.
[0063] In this example depicted in FIG. 4, the actuator exerting a
force on the membrane element 33 is a voice coil. The voice coil is
used to transmit a reciprocating stroke motions by the pump head 12
to the membrane element 33. Specifically, the voice coil may be a
cylindrical voice coil.
[0064] In one example, the coil 13 is a circular cylinder
structure, which is fixed on the pump head 12 and placed in an air
gap. The air gap is enclosed by a magnetic cup with conical bottom
7, a conical magnet 8, such as a permanent magnet, and a one side
conical pole shoe 9.
[0065] Additionally, in order to maximize the utilization of the
magnetic field in the air gap and reduce the size of the pump 300,
the coil 13 may be a skeletonless coil, entwined by self-adhesive
lining. This design may take advantage of the limit space of the
air gap, hence it's possible to design smaller membrane pumps
300.
[0066] In the example illustrated in FIG. 4, the magnet cup with a
conical bottom 7 is positioned as an inverted M-shape. The contact
surface between the conical pole shoe 9, the conical magnet 8 and
the contact surface between the conical magnet and conical bottom
of the magnet cup 7 are all tapered. The tapered surfaces are
tapered in the same direction. Such structure increases the side
area of the conical pole shoe 9, making the magnetic field in the
air gap distribute evenly radially.
[0067] This design allows for a larger magnet, better distribution
of the magnetic flux inside the pole shoe 9. Further, the conical
shape provides better support for the free shaft of the pump head
12 without adding any volume outside of the cylinder volume. Thus
the magnetic field is as large as possible when the coil 13 works
in the air gap.
[0068] In FIG. 4, the working principle of the membrane pump 300
is: the coil 13 positioned in the magnetic field formed by the one
side conical pole shoe 9, the conical magnet 8 and the magnet cup
with conical bottom 7. When an alternating voltage is transmitted
to the coil 13, the coil 13 will produce an alternating ampere
force to drive the pump head 12 in reciprocating linear motion.
[0069] The pump cycle will produce a cycle of positive and negative
pressure in the pump chamber 21. When pressure in the sealed room
is negative, fluid will move through a pump inlet into the chamber
21. When pressure in the sealed room is positive, the pump 300 will
move fluid out through an outlet.
[0070] In the example illustrated in FIG. 4, a small voice coil is
adopted to drive membrane to do linear motion so that large
transmission mechanisms are eliminated. Thus the size of the
membrane pump 300 is reduced. The voice coil does not affect the
working life of the pump 300, because the voice coil does not
comprise structures that are easily worn out. The voice coil drives
the membrane element 33 directly without the process of
transforming motion to another; hence no intermediate energy is
consumed. Further, there is no starting torque problem; hence the
pump 300 may start almost instantly by applying a small voltage.
The voice coil therefore also output a force or a displacement of
the pump head 12 to collect a small volume of fluid even at small
driving voltage or current.
[0071] Also, the reciprocating motion of the pump head 12 is
controlled by controlling the frequency of the voltage. Because the
magnitude of reciprocating motion is dependent to the amplitude of
the current, the collected flow size may be easily controlled by
adjusting the amplitude of the voltage to the voice coil.
[0072] While several embodiments of the present disclosure have
been described and illustrated herein, those of ordinary skill in
the art will readily envision a variety of other means and/or
structures for performing the functions and/or obtaining the
results and/or one or more of the advantages described herein, and
each of such variations and/or modifications is deemed to be within
the scope of the present disclosure. More generally, those skilled
in the art will readily appreciate that all parameters, dimensions,
materials, and configurations described herein are meant to be
exemplary and that the actual parameters, dimensions, materials,
and/or configurations will depend upon the specific application or
applications for which the teachings of the present disclosure
is/are used. Also, different method steps than those described
above, performing the method by hardware, may be provided within
the scope of the disclosure. The different features and steps of
the disclosure may be combined in other combinations than those
described. The scope of the invention is only limited by the
appended patent claims
* * * * *