U.S. patent application number 12/110893 was filed with the patent office on 2008-10-30 for solenoid pump.
This patent application is currently assigned to Johnson Electric S.A.. Invention is credited to Bao Ting Liu, Guo Ji Zhang.
Application Number | 20080267798 12/110893 |
Document ID | / |
Family ID | 39591763 |
Filed Date | 2008-10-30 |
United States Patent
Application |
20080267798 |
Kind Code |
A1 |
Liu; Bao Ting ; et
al. |
October 30, 2008 |
SOLENOID PUMP
Abstract
A method of reducing or eliminating vibration in a linear
reciprocating solenoid pump 10, the method comprising the steps of
providing a solenoid pump 10 having a linear reciprocating plunger
14 and providing an electric circuit 48 to energize electro-motion
means 16 of the solenoid pump 10, the electric circuit 48
energizing the electro-motion means 16 with an increased frequency
of n times the frequency of normal mains electricity.
Inventors: |
Liu; Bao Ting; (Shenzhen,
CN) ; Zhang; Guo Ji; (Shenzhen, CN) |
Correspondence
Address: |
Muncy, Geissler, Olds & Lowe, PLLC
P.O. BOX 1364
FAIRFAX
VA
22038-1364
US
|
Assignee: |
Johnson Electric S.A.
|
Family ID: |
39591763 |
Appl. No.: |
12/110893 |
Filed: |
April 28, 2008 |
Current U.S.
Class: |
417/416 |
Current CPC
Class: |
F04B 49/06 20130101;
F04B 49/20 20130101; F04B 35/045 20130101; F04B 2203/0404 20130101;
F04B 39/0027 20130101; F04B 2203/0406 20130101 |
Class at
Publication: |
417/416 |
International
Class: |
F04B 17/04 20060101
F04B017/04 |
Foreign Application Data
Date |
Code |
Application Number |
Apr 28, 2007 |
CN |
200710100946.5 |
Claims
1. A method of reducing or eliminating vibration in a linear
reciprocating solenoid pump, the method comprising the steps of:
providing a solenoid pump having a linear reciprocating plunger;
and providing an electric circuit to energize electro-motion means
of the solenoid pump, the electric circuit energizing the
electro-motion means with an increased frequency of n times normal
mains electricity frequency.
2. The method of claim 1, wherein n is a whole number greater than
1.
3. The method of claim 1, wherein the electric circuit includes a
full bridge rectifier and a MOSFET to provide the increased
frequency.
4. The method of claim 1 comprising providing the electric circuit
with a bidirectional thyristor connected in series with the
electro-motion means.
5. The method of claim 1, further comprising selecting n to avoid
operating the pump at its natural resonance frequency.
6. A solenoid pump comprising: a pump housing having a liquid
inlet, a liquid outlet, and a plunger chamber; a plunger received
for linear reciprocating movement in the plunger chamber;
electro-motion means for electromagnetically moving the plunger;
and an electric circuit for energizing the electro-motion means
with a frequency n times greater than normal mains electricity
frequency, where n is a number greater than 1.
7. The solenoid pump of claim 6, wherein the plunger is hollow and
includes a plunger head which is slidably received in the plunger
chamber and an elongate plunger rod which is slidably received in a
pump chamber.
8. The solenoid pump of claim 6, wherein the electric circuit
includes a full bridge rectifier and a MOSFET for providing the
increased frequency.
9. The solenoid pump of claim 6, wherein the electric circuit
includes a bidirectional thyristor in series with a coil of the
electro-motion means.
10. The solenoid pump of claim 6, wherein n is a whole number
greater than 1.
11. The solenoid pump of claim 10, wherein the increased frequency
is different to the natural resonance frequency of the pump.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This non-provisional patent application claims priority
under 35 U.S.C. .sctn.119(a) from Patent Application No.
200710100946.5 filed in China on 28 Apr. 2007.
BACKGROUND OF THE INVENTION
[0002] This invention relates to solenoid pumps and more
particularly to reducing or eliminating vibration and/or noise
caused during operation.
[0003] Solenoid pumps are well known, and typically comprise a pump
housing and a linear reciprocating plunger slidable therein to pump
liquid between an inlet and an outlet.
[0004] However, vibration caused by the unbalanced movement of the
mass of the plunger, and consequently noise associated therewith,
is undesirable and can result in premature fatigue, wear and
failure of the pump.
[0005] The present invention seeks to overcome or mitigate this
problem.
SUMMARY OF THE INVENTION
[0006] According to a first aspect of the invention, there is
provided a method of reducing or eliminating vibration in a linear
reciprocating solenoid pump, the method comprising the steps of:
[0007] providing a solenoid pump having a linear reciprocating
plunger; and [0008] providing an electric circuit to energize
electro-motion means of the solenoid pump, the electric circuit
energizing the electro-motion means with an increased frequency of
n times normal mains electricity frequency.
[0009] Preferably, n is chosen to avoid operating the pump at its
natural resonance frequency.
[0010] Preferably, n is a whole number greater than 1.
[0011] Preferably, the electric circuit includes a full bridge
rectifier and a MOSFET to provide the increased frequency.
[0012] Alternatively, the electric circuit includes a bidirectional
thyristor connected in series with the electro-motion means.
[0013] According to a second aspect of the invention, there is
provided a solenoid pump comprising: a pump housing having a liquid
inlet, a liquid outlet, and a plunger chamber; a plunger received
for linear reciprocating movement in the plunger chamber;
electro-motion means for electromagnetically moving the plunger;
and an electric circuit for energizing the electro-motion means
with a frequency n times greater than normal mains electricity
frequency, where n is a number greater than
[0014] Preferably, the plunger is hollow and includes a plunger
head which is slidably received in the plunger chamber and an
elongate plunger rod which is slidably received in a pump
chamber.
[0015] Preferably, the electric circuit includes a full bridge
rectifier and a MOSFET for providing the increased frequency.
[0016] Alternatively, the electric circuit includes a bidirectional
thyristor in series with a coil of the electro-motion means.
[0017] Preferably, the increased frequency is different to the
natural resonance frequency of the pump.
[0018] Preferably, n is a whole number greater than 1.
BRIEF DESCRIPTION OF THE DRAWINGS
[0019] Embodiments of the present invention will now be more
particularly described, by way of example only, with reference to
the accompanying drawings, in which:
[0020] FIG. 1 shows a cross-sectional plan view of one embodiment
of a solenoid pump, in accordance with the second aspect of the
invention;
[0021] FIG. 2 shows a first electric circuit used to energize the
solenoid pump;
[0022] FIG. 3 illustrates time graphs of various parts of the
circuit of FIG. 2;
[0023] FIG. 4 shows a second electric circuit used to energize the
solenoid pump; and
[0024] FIG. 5 illustrates time graphs of various parts of the
circuit of FIG. 4.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0025] Referring firstly to FIG. 1 of the drawings, there is shown
a solenoid pump 10 which comprises a pump housing 12, a linear
reciprocatable plunger 14, and electro-motion means 16 for moving
the plunger 14 in a reciprocating manner. The electro-motion means
is preferably, in the form of a solenoid.
[0026] The pump housing 12 includes a hollow housing body 18 having
two open ends 20 and a stepped-bore 22 therethrough. A plunger
chamber 24 is provided within the housing body 18 and is defined
primarily by the stepped-bore 22. A first one of the open ends 20
of the housing body 18 forms a liquid inlet port 26 for liquid flow
into the plunger chamber 24, and an end cap 28 is fastened,
typically by bolts, to the housing body 18 to close a second one of
the open ends 20.
[0027] The end cap 28 includes a central rectilinear liquid-outlet
passage 30 therethrough. The liquid-outlet passage defines a pump
chamber 32 leading from the plunger chamber 24. The plunger chamber
24 is cylindrical and the pump chamber 32 is coaxially aligned with
the cylinder axis of the plunger chamber 24. The liquid outlet port
26 is shown as also being coaxially aligned.
[0028] The plunger 14 is hollow and comprises a plunger head 34 and
an elongate hollow plunger rod 36 rigidly fixed to the plunger head
34. The plunger head 34 includes a recess 35 with an opening in a
base of the recess. The plunger rod 36 includes an axially
extending uniform through-bore 37, with one end being received in
the opening in the base of the recess 15. A lateral cross-section
of the through-bore of the plunger rod 36 is smaller than a lateral
cross-section of the recess of the plunger head 34. In this way, a
stepped through-bore through the plunger 14 is formed by the recess
of the plunger head 34 and the through-bore of the plunger rod 36.
The plunger head 34 is a sliding fit within the plunger chamber 24.
Holes 41 are provided to equalize fluid pressure within the plunger
chamber on either side of the plunger head.
[0029] A coiled return spring 38 is included within the plunger
chamber 24. The return spring 38 extends from the plunger head 34
to contact the first open end 20 adjacent to the liquid inlet port
26. A step in the stepped base 22, provides a seal for the return
spring 38. The return spring 38 biases the plunger head 34 towards
the pump chamber 32.
[0030] A coiled buffer spring 40 is also included within the
plunger chamber 24, interposed between the plunger head 34 and the
end cap 28. The plunger rod 36 extends coaxially within the buffer
spring 40. The in use buffer spring 40 prevents the plunger head 34
from contacting the associated end cap 28. A plate or disc 54
provides a seat for the buffer spring 40. Disc 54 may be of a
rubber based material to further dampen vibrations from the plunger
14 and buffer spring 40 being transferred to the end cap and
housing.
[0031] The plunger rod 36 is dimensioned to be a clearance sliding
fit within the pump chamber 32. A seal 33, preferably in the form
of a rubber O-ring, seals the plunger rod 36 to the pump chamber 32
while allowing the plunger rod to slide with respect to the pump
chamber 32 along the plunger axis. The seal 33 is held on a step in
the pump chamber 32 by a seal retainer 43. In this way, the seal 33
also acts as a plunger guide, stabilising the plunger 14 during
use.
[0032] The plunger rod 36 thus has an open end disposed within the
pump chamber 32. The open end is closed by a non-return valve 56
formed by a seal body 58 which is pressed against the open end of
the plunger rod by a valve spring 60. The non-return valve 56
allows fluid to enter the pump chamber 32 through the hollow
plunger rod 36 but cannot exit the pump chamber via the plunger
rod.
[0033] A restriction in the bore of the pump chamber 32 forms an
outlet port which is fitted with a non-return valve 62 having a
spring 60 and a seal body 58, which is pressed against the outlet
port to prevent liquid entering the pump chamber 32 through the
outlet port. Spring 60 is held in the outlet passage 30 by a
retaining tube pressed into the outlet passage 30.
[0034] In operation, sliding movement of the plunger rod causes
fluid to be pumped through the pump chamber. As the plunge rod is
withdrawn partially from the pump chamber, liquid enters the pump
chamber through the plunger rod to fill up the space left by the
withdrawing plunger rod. When the plunger rod is moved in the
opposite direction, to be inserted further into the pump chamber,
the displaced liquid is expelled through the outlet port with the
non-return valve preventing liquid movement in the opposite
direction.
[0035] The electro-motion means 16 includes an electromagnetic
stator 42 comprised of an annular electromagnet 44 supported by and
surrounding the housing body 18 of the solenoid pump 10 on an
exterior surface thereof, an armature 46 comprised of the plunger
head 34 and formed of an electromagnetic material, and an electric
circuit 48 for energizing the electromagnetic stator 42.
[0036] In use, the electromagnet 44 is energized with electrical
current in a pulsating manner. This current, when flowing through
the coil of the electromagnet, causes a magnetic field to be
generated which, due to the electromagnetic stator, causes the
plunger to be drawn to the right (as shown in FIG. 1) against the
urgings of the return spring 38 to align the plunger head,
functioning as the armature, into the gap 45 formed in the magnetic
path of the stator. When the current through the coil is turned
off, the armature is released and the plunger is moved to the left
(as shown in FIG. 1) under the resilient urgings of the return
spring and as buffered by the buffer spring 40. Movement of the
plunger head causes movement of the plunger rod as discussed above
to pump liquid through the pump chamber.
[0037] Traditionally, the coil is connected to mains supply via a
diode providing a half wave rectified waveform giving a simple
pulse for each cycle of the mains power, thus also providing a half
cycle rest period for the return spring to pump the liquid out of
the pump chamber.
[0038] The present invention modifies the input wave form so as to
increase the number of pulses per cycle of mains frequency while
still giving sufficient rest time between pulses for the return
spring to move the plunger when the electromagnet relaxes so as to
do useful work. Vibration is reduced by having a lower stroke
length of the plunger but pump volume (capacity) is not sacrificed
due to the higher pumping frequency.
[0039] Although many complex circuits are available for modifying
voltage waveforms and changing the frequency of mains power, two
simple circuits will be discussed which each provide a doubling of
the operating frequency of the solenoid pump.
[0040] FIG. 2 illustrates a first preferred circuit 48. Mains power
is connected across a full wave bridge rectifier 50 to generate the
typical rectified waveform of FIG. 3(a). The output of the bridge
rectifier 50 is applied to a series connected circuit of the
solenoid 10 and a MOSFET 51. A flywheel diode 72 and resistor 73
are placed across the solenoid. A voltage divider resistor network,
resistors 70, 71 are connected across the bridge output to provide
a reduced voltage to the Gate terminal of the MOSFET 51. Thus, when
the voltage of the divider circuit is higher than the open voltage
of the Gate terminal, the MOSFET turns ON and the solenoid is
energized. Otherwise, the MOSFET is OFF and the solenoid id
de-energized. The ON/OFF time of the MOSFET is shown in FIG. 3(b)
and the solenoid current wave form is shown in FIG. 3(c) where the
decay current through the flywheel diode is noted.
[0041] The ON/OFF time of the MOSFET can be adjusted by changing
the values of the divider resisters 70, 71. Thus, the pump operates
at 2 times the inputted mains power frequency.
[0042] The circuit of FIG. 4 illustrates another preferred circuit
48a. AC mains frequency power is applied across a series circuit of
the solenoid coil 10 and a bidirectional thyristor 52. The input
voltage waveform is shown in FIG. 5(a). Two resistors 74, 75 and a
capacitor 76 are arranged to form a delay trigger circuit to the
Gate terminal of the thyristor. When the voltage across the
thyristor is close to the maximum value, the thyristor is turned ON
and the solenoid is energized. The thyristor once triggered stays
on until the current through it becomes zero (as occurs when the
voltage changes polarity). The ON/OFF time of the thyristor 52 is
shown in FIG. 5(b) and the current through the solenoid is shown in
FIG. 5(c). The solenoid is, of course, de-energized when the
thyristor 52 turns OFF.
[0043] Once the solenoid is energized, whether by positive or
negative current, it will induce a magnetic field attracting the
plunger, thus compressing the return spring. During the OFF time,
the spring relaxes pushing the plunger into the pump chamber to
pump the liquid. Thus again, the pump operates at twice mains
frequency.
[0044] Although the drive circuits can be, in theory, applied to a
standard solenoid pump, in practice, the plunger and springs are
configured to operate at a desired frequency and the mass of the
plunger is chosen to have a natural resonance frequency greater
than the operating frequency but not significantly greater to give
the plunger a certain momentum during operation. By simply changing
the operating frequency, there is a possibility that the pump will
not work or will go into natural resonance and generate
uncontrolled vibrations.
[0045] As resonance frequency is proportional to the square root of
the reciprocal of mass, it may be desirable, as a rough
calculation, to reduce the mass of the plunger by a factor of n 1/m
where n=the number of times the mains frequency is increased, i.e.
f.sub.o=nf.sub.m where f.sub.o=operating frequency, f.sub.m=mains
frequency, n=integer, so as to maintain the natural frequency
higher than the operating frequency.
[0046] However, as most pump designs are not so finely tuned, for a
doubling of input frequency, a halving of plunger mass and plunger
stroke length will produce a pump with similar output and
significantly reduced vibrations making this design a good solution
for improving solenoid pump designs.
[0047] The plunger stroke length can be modified by changing the
spring force and the electro-magnetic power of the solenoid.
[0048] It has been determined that, when vibration occurs in a
normal standard solenoid pump 10 having a single linear
reciprocating plunger 14, the vibration and thus generated noise
can be eliminated, or at the very least significantly reduced, by
reducing the mass of the plunger 14 by 1/n times, by then reducing
the amplitude of movement of the plunger 14 by 1/n times, and
finally by increasing the frequency of the electricity applied to
the electromagnetic stator 42 to n times normal mains
frequency.
[0049] This inter-relationship provides for markedly reduced, or
elimination of, vibration and consequently noise.
[0050] The mass of the plunger can be easily altered by standard
manufacturing or workshop techniques, for example by altering the
material of manufacture or by removing material via machining.
[0051] Although the mass of the plunger and its operating amplitude
are reduced, the pumping rate is not significantly impacted.
Consequently, the reduced or eliminated vibration, resulting in
improved reliability and longevity, is preferred.
[0052] Although n has been suggested above as being 2, n can be any
number which is greater than 1. Also, preferably, n is a whole
number. Ideally, n can be chosen to avoid the natural resonance
frequency of the pump.
[0053] An actual optimum value of n for a particular series of
solenoid pumps can be derived by monitoring the pump, and then
making appropriate changes to the mass of the plunger and the
associated energizing circuitry. As such, it may be found that, for
a particular series of pumps, n may be 3 or even 4.
[0054] It will also be appreciated that any circuit means can be
provided for energizing the electromagnetic stator of the
electro-motion means, providing the amplitude of the plunger and
the frequency of the electrical energization can be controlled and
set.
[0055] The embodiments described above are given by way of example
only, and various other modifications will be apparent to persons
skilled in the art without departing from the scope of the
invention, as defined by the appended claims.
* * * * *