U.S. patent application number 14/125134 was filed with the patent office on 2014-04-24 for pump assembly.
This patent application is currently assigned to DELPHI TECHNOLOGIES HOLDING S.A.R.L.. The applicant listed for this patent is Keith E. Wright. Invention is credited to Keith E. Wright.
Application Number | 20140112806 14/125134 |
Document ID | / |
Family ID | 44358148 |
Filed Date | 2014-04-24 |
United States Patent
Application |
20140112806 |
Kind Code |
A1 |
Wright; Keith E. |
April 24, 2014 |
PUMP ASSEMBLY
Abstract
A pump assembly for use in a selective catalytic reduction
system, the pump assembly comprising: a pump sub-assembly defining
a pump axis; and a housing sub-assembly including a cavity for
receiving the pump sub-assembly and comprising an inlet port for
receiving a reagent for supply to the pump sub-assembly via a flow
path; wherein at least one seal member is provided to seal the pump
sub-assembly within the housing sub-assembly, the seal member being
provided in a groove in an outer face of the pump sub-assembly, the
seal member providing a fluid tight seal.
Inventors: |
Wright; Keith E.; (Kent,
GB) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Wright; Keith E. |
Kent |
|
GB |
|
|
Assignee: |
DELPHI TECHNOLOGIES HOLDING
S.A.R.L.
BASCHARAGE
LU
|
Family ID: |
44358148 |
Appl. No.: |
14/125134 |
Filed: |
June 20, 2012 |
PCT Filed: |
June 20, 2012 |
PCT NO: |
PCT/EP2012/061853 |
371 Date: |
December 10, 2013 |
Current U.S.
Class: |
417/415 ;
29/888.02 |
Current CPC
Class: |
Y02T 10/24 20130101;
Y10T 29/49236 20150115; F01N 3/2066 20130101; Y02T 10/12 20130101;
F04B 17/04 20130101; F01N 2610/1433 20130101 |
Class at
Publication: |
417/415 ;
29/888.02 |
International
Class: |
F04B 17/04 20060101
F04B017/04 |
Foreign Application Data
Date |
Code |
Application Number |
Jun 28, 2011 |
EP |
11171730.2 |
Claims
1. A pump assembly for use in a selective catalytic reduction
system, the pump assembly comprising: a pump sub-assembly defining
a pump axis; and a housing sub-assembly including a cavity for
receiving the pump sub-assembly and comprising an inlet port for
receiving a reagent for supply to the pump sub-assembly via a flow
path; wherein at least one seal member is provided to seal the pump
sub-assembly within the housing sub-assembly, the seal member being
provided in a groove in an outer face of the pump sub-assembly, the
seal member providing a fluid tight seal and wherein the pump
sub-assembly comprises a pump core, an outer pole member and a
solenoid coil, the core, pole member and coil being provided within
a coil over-moulding member.
2. A pump assembly as claimed in claim 1, further comprising a
compartment defined in part by the pump and housing sub-assemblies
wherein the at least one seal member comprises a compartment seal
member arranged to separate the compartment and flow path, the
compartment seal member being provided in a groove in an outer face
of the pump sub-assembly, the compartment seal member providing a
fluid tight seal between the compartment and the flow path.
3. A pump assembly as claimed in claim 1, wherein the housing
sub-assembly comprises a drilling having an opening in an outer
surface of the housing sub-assembly, and the pump sub-assembly
comprises a neck portion of substantially complementary shape to
the drilling wherein the at least one seal member comprises a
drilling seal member arranged to seal the neck portion in the
drilling, the drilling seal member being provided in a groove in an
outer face of the neck portion of the pump sub-assembly and
providing a fluid tight seal between the opening of the drilling
and the flow path.
4. A pump assembly as claimed in claim 3, wherein the neck portion
is disposed about the pump axis and defines a bore arranged to
receive electrical connector means for connection to a solenoid
coil.
5. A pump assembly as claimed in claim 1, wherein the over-moulding
member is formed from plastic.
6. A pump assembly as claimed in claim 1, wherein the flow path
comprises one or more flow ports provided through the body of the
over-moulding member.
7. A pump assembly as claimed in claim 6, wherein a reagent gallery
is defined between the housing and pump sub-assemblies, the one or
more flow ports being arranged to open into the gallery and the
gallery being in fluid communication with the inlet port.
8. A pump assembly as claimed in claim 7, wherein the housing
sub-assembly defines a reagent passage from the inlet port to the
gallery, the flow path being provided by the reagent passage, the
gallery and the one or more flow ports.
9. A pump assembly as claimed in claim 6, wherein the body of the
over-moulding member comprises a plurality of flow ports.
10. A pump assembly as claimed in claim 9, wherein the pump
sub-assembly comprises a metallic back plate having one or more
drillings, each flow port being arranged to align with a
drilling.
11. A pump assembly as claimed in claim 9, wherein a solenoid coil
cable from an electrical connector means for connection to a
solenoid coil is routed through the over-moulding member between
reagent flow ports to the solenoid coil.
12. A method of manufacturing a pump assembly comprising
manufacturing a pump sub assembly by: providing a blank disk member
of a material having a relatively high magnetic permeability; deep
drawing the blank disk member to form an outer pole piece, the
outer pole piece defining an internal volume with an opening;
providing a coil former, the coil former defining an internal
volume; winding coil wire onto the coil former to form a solenoid
coil; inserting the solenoid coil into the internal volume of the
outer pole piece; pressing a back stop plate into the outer pole
piece, the back stop plate having at least one drilling through the
plate; injection moulding an over-mould member to encapsulate the
outer pole piece and solenoid coil; forming at least one flow port
through the over-moulding member, the at least one flow port
aligning with the at least one drilling in the back stop plate;
forming at least one groove in the outer face of the over-mould
member.
13. A method as claimed in claim 12, further comprising inserting
an actuator pump core into the internal volume of the coil
former.
14. A method as claimed in claim 12 comprising placing an O ring
sealing member into the at least one groove in the outer face of
the over-mould member and inserting the pump sub-assembly into a
housing sub-assembly.
Description
FIELD OF THE INVENTION
[0001] The present invention relates to a pump assembly. More
particularly, but not exclusively, the invention relates to a
dosing pump for a selective catalytic reduction system.
BACKGROUND TO THE INVENTION
[0002] It is known that exhaust gases from internal combustion
engines contain substances which are harmful to the environment and
which can pose a threat to public health. For many years, a
sustained effort has been made within the automotive industry to
reduce the release to the atmosphere of harmful substances carried
in exhaust gases, both by modifying the combustion process itself
to give a reduced yield of harmful combustion products, and by
treating the exhaust gases before their emission into the
atmosphere, for example by providing a catalyst to induce chemical
breakdown of the harmful constituents, particularly the oxides of
nitrogen (NO.sub.x), into benign compounds.
[0003] One strategy for reducing NO.sub.x emissions, known as
selective catalytic reduction or SCR, involves the introduction of
a reagent comprising a reducing agent, typically a liquid ammonia
source such as an aqueous urea solution, into the exhaust gas
stream. The reducing agent is injected into the exhaust gas
upstream of an exhaust gas catalyst, known as an SCR catalyst,
typically comprising a mixture of catalyst powders such as titanium
oxide, vanadium oxide and tungsten oxide immobilised on a ceramic
honeycomb structure. Nitrogen oxides in the exhaust gas undergo a
catalysed reduction reaction with the ammonia source on the SCR
catalyst, forming gaseous nitrogen and water. An example of an SCR
system is described in the Applicant's European Patent Application
Publication No. EP-A-2131020, which corresponds to U.S. Patent
Application Publication No. 2009/0301067A1.
[0004] SCR systems typically include a reagent dosing pump for
delivering reagent to the exhaust gas stream.
[0005] In one known reagent dosing pump, a solenoid-actuated
pumping arrangement is provided to increase the pressure of the
reagent, and the pump includes an atomising nozzle that receives
the reagent from the pumping arrangement and delivers it from an
outlet end into the exhaust gas stream. The nozzle is close-coupled
to the pumping arrangement, so that the nozzle and the pumping
arrangement form a single unit. The outlet end of the nozzle may be
positioned directly in the exhaust gas stream, so that the pumping
arrangement is located close to the outside of the exhaust pipe
that conveys the exhaust gases.
[0006] Examples of such pumps are described in the Applicant's
European Patent Application Publication No. EP-A-1878920, which
corresponds to U.S. Patent Application Publication No.
2008/0014103A1.
[0007] The pumping work conducted by the dosing arrangement of such
solenoid actuated pumps is created by a solenoid coil acting on the
magnetic armature of a plunger armature assembly.
[0008] The maximum temperature at which urea-based reducing agents
can be used is somewhat limited. Urea crystals tend to precipitate
when the temperature of the solution is greater than approximately
70.degree. C. Precipitation is undesirable because the precipitates
can cause blockages in the delivery system, for example in the
small-diameter outlets typically provided in the outlet end of the
atomising nozzle. In addition, the formation of precipitates alters
the concentration of the remaining solution, so that the effective
quantity of ammonia delivered to the exhaust flow becomes
uncertain. This could lead to inefficient catalysis and an
insufficient reduction in NO.sub.x emissions.
[0009] It is therefore desirable, in many cases, to provide cooling
means to cool the reagent in an SCR system and, in particular, in
the reagent dosing pump, to prevent overheating of the reagent.
Furthermore, when solenoid-actuated pumping arrangements are used,
it is also desirable to cool the solenoid coil since the
performance of solenoid actuators can decrease at high
temperatures. Many known pump assembly arrangements therefore
include a water cooling system, e.g. by means of the provision of a
water jacket around the solenoid actuator and the provision of
water input and output ports to the jacket in order to provide a
flow of cooling water.
[0010] In designing and optimising pump assemblies there are a
number of requirements that need to be considered. Firstly,
packaging of the pump assembly within the engine system is
increasingly challenging. The mass of such an assembly is also
important in ensuring the product is robust in its attachment to a
thin walled exhaust section, and subsequent vibrations seen in use.
And finally, one further issue which is important to the
integration of a new water cooled product in such an environment is
the heat input in to the water cooling system.
[0011] One area which drives opportunities to improve all of the
above points is size and arrangement of the solenoid coil. On the
design described in EP1878920, a terminal block is provided to
interface between the coil windings of the solenoid coil of the
actuator and an electrical supply cable (the solenoid cable).
However, this approach increases the packaging size of the coil,
and hence the water jacket required to house it. There is therefore
a knock on effect which impacts the size, mass and surface area of
the doser exposed to the high ambient temperature environment.
[0012] It is therefore an object of the present invention to
provide a pump assembly for use in an engine system that
substantially overcomes or mitigates the above mentioned
problems.
SUMMARY OF THE INVENTION
[0013] According to a first aspect of the present invention there
is provided a pump assembly for use in a selective catalytic
reduction system, the pump assembly comprising: a pump sub-assembly
defining a pump axis (A); and a housing sub-assembly including a
cavity for receiving the pump sub-assembly and comprising an inlet
port for receiving a reagent for supply to the pumping sub-assembly
via a flow path; wherein at least one seal member is provided to
seal the pump sub-assembly within the housing sub-assembly, the
seal member being provided in a groove in an outer face of the pump
sub-assembly, the seal member providing a fluid tight seal and
wherein the pump sub-assembly comprises a pump core, an outer pole
member and a solenoid coil, the core, pole member and coil being
provided within a coil over-moulding member.
[0014] The present invention provides a pump assembly which seeks
to simplify assembly by substantially moving the complexity to one
outsourced subassembly. In particular, the invention provides a
pump assembly comprising housing and pump sub-assemblies in which
an outer surface of the pump sub-assembly is provided with grooves
for receiving seal member(s) to provide fluid tight seals within
the pump assembly. By providing the seal members within grooves
located on one component (the pump sub-assembly) the level of
machining necessary in the housing sub-assembly (which would
generally be made of a cast metal) is reduced which reduces the
complexity of the housing sub-assembly and also saves costs on
producing the housing.
[0015] The pump assembly may conveniently comprise seal member(s)
between internal sections of the pump assembly to provide fluid
tight seals between the reagent and, for example, a cooling fluid
such as water. In such an arrangement therefore the pump assembly
conveniently further comprises a compartment defined in part by the
pump and housing sub-assemblies wherein the at least one seal
member comprises a compartment seal member arranged to separate the
compartment and flow path, the compartment seal member being
provided in a groove in an outer face of the pump sub-assembly, the
compartment seal member providing a fluid tight seal between the
compartment and the flow path.
[0016] The pump assembly may also conveniently comprise seal
member(s) between an internal section of the pump assembly and an
opening in the housing sub-assembly. In such an arrangement
therefore the housing sub-assembly may conveniently comprise a
drilling having an opening in an outer surface of the housing
sub-assembly, and the pump sub-assembly comprises a neck portion of
substantially complementary shape to the drilling wherein the at
least one seal member comprises a drilling seal member arranged to
seal the neck portion in the drilling, the drilling seal member
being provided in a groove in an outer face of the neck portion of
the pump sub-assembly and providing a fluid tight seal between the
opening of the drilling and the flow path.
[0017] The neck portion may be disposed about axis A and define a
bore arranged to receive electrical connector means for connection
to a solenoid coil. The axis of the bore may be coincident with
axis A.
[0018] Preferably the over-moulding member may be formed from
plastic. It is noted that the plastic over-moulding member may be
processed more easily than the housing sub-assembly to provide the
grooves required to receive the seal members.
[0019] Conveniently the flow path comprises one or more flow ports
provided through the body of the over-moulding member.
[0020] Conveniently a reagent gallery may be defined between the
housing and pump sub-assemblies, the one or more flow ports being
arranged to open into the gallery and the gallery being in fluid
communication with the inlet port.
[0021] Conveniently the housing sub-assembly may define a reagent
passage from the inlet port to the gallery, the flow path being
provided by the reagent passage, the gallery and the one or more
flow ports.
[0022] In order to improve reagent flow into the pump assembly the
body of the over-moulding member may comprise a plurality of flow
ports.
[0023] Where the pump sub-assembly comprises a metallic back plate,
the back plate preferably comprises one or more drillings arranged
such that each flow port aligns with a drilling.
[0024] Where the pump assembly is connected to an electrical
connector member the electrical connections provided by the member
(the solenoid coil cable) may conveniently be routed through the
over-moulding member in between the reagent flow ports leading to
the solenoid coil.
[0025] According to a second aspect of the present invention there
is provided a method of manufacturing a pump assembly comprising
manufacturing a pump sub assembly by: providing a blank disk member
of a material having a relatively high magnetic permeability; deep
drawing the blank disk member to form an outer pole piece, the
outer pole piece defining an internal volume with an opening;
providing a coil former, the coil former defining an internal
volume; winding coil wire onto the coil former to form a solenoid
coil; inserting the solenoid coil into the internal volume of the
outer pole piece; pressing a back stop plate into the outer pole
piece, the back stop plate having at least one drilling through the
plate; injection moulding an over-mould member to encapsulate the
outer pole piece and solenoid coil; forming at least one flow port
through the over-moulding member, the at least one flow port
aligning with the at least one drilling in the back stop plate;
forming at least one groove in the outer face of the over-mould
member.
[0026] The method may further comprise inserting an actuator pump
core into the internal volume of the coil former.
[0027] The method may further comprise placing an O ring sealing
member into the at least one groove in the outer face of the
over-mould member and inserting the pump sub-assembly into a
housing sub-assembly.
[0028] Preferred and/or optional features of each aspect of the
invention may be used, alone or in appropriate combination, in the
other aspects also.
BRIEF DESCRIPTION OF THE DRAWINGS
[0029] Embodiments of the present invention will now be described,
by way of example only, with reference to the accompanying
drawings, in which like reference numerals are used for like parts,
and in which:
[0030] FIG. 1 shows a known pump assembly;
[0031] FIG. 2 shows a pump assembly according to an embodiment of
the present invention.
DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION
[0032] A known pump assembly 10 is shown in FIG. 1.
[0033] Referring FIG. 1, the pump assembly 10 includes a reagent
dosing unit with an integrated pump and nozzle arrangement,
referred to hereafter as a reagent dosing pump sub-assembly 12. The
pump sub-assembly 12 is a reagent dosing pump of any suitable type,
for example as described in EP-A-1878920, to which reference can be
made for further details of the pump sub-assembly 12.
[0034] The pump sub-assembly 12 comprises a pump housing 14 having
a generally cylindrical pump body portion 16 that defines a pump
axis (axis A in FIG. 1), and a generally cylindrical nozzle portion
18 that extends from a first face 20 of the body portion 16 along
the pump axis A. The nozzle portion 18 has a relatively small
diameter compared to the body portion 16.
[0035] The body portion 16 of the pump housing 14 houses a pumping
mechanism (not shown), such as a solenoid-actuated pumping
mechanism. In use, the pumping mechanism receives reagent through a
reagent inlet 22 provided on a second face 24 of the body portion
16, opposite the first face 20. An electrical connection point 26
is also located on the second face 24 of the body portion 16, to
provide an operating current to the solenoid actuator of the
pumping mechanism. As is known from EP-A-1878920, the pumping
mechanism includes a reciprocating pumping element, such as a
plunger or piston, and is arranged to increase the pressure of a
pre-defined quantity of reagent on each cycle of the pumping
element.
[0036] The nozzle portion 18 of the pump housing 14 houses a
delivery passage (not shown) that, in use, receives the pressurised
reagent from the pumping mechanism, and conveys it to a
reduced-diameter outlet end 28 of the nozzle portion 18. The outlet
end 28 houses an atomising nozzle that atomises the reagent as it
exits the pump sub-assembly 12.
[0037] The pump assembly 10 also includes a housing sub-assembly 30
having an internal cavity 32 in which the pump 12 is received. The
cavity 32 is defined by an internal wall 34 of the housing
sub-assembly 30. In general terms, the shape of the cavity 32 is an
enlarged version of the shape defined by the pump housing 14. In
this way, the internal wall 34 of the cavity 32 is spaced from the
pump housing 14 to define a volume/compartment 36 for cooling fluid
therebetween.
[0038] The housing sub-assembly 30 is generally made from cast
stainless steel.
[0039] In a region of the housing sub-assembly 30 remote from the
outlet end 18 of the pump, a projection or land 40 extends axially
from the internal wall 34 of the cavity 32 towards the outlet end
18 of the pump, to meet the inlet port 22 on the second face 24 of
the housing pump body portion 16. A collar 42 is provided on the
second face 24 of the pump body portion 16 that receives the land
40. An O-ring 44 is provided to create a fluid-tight seal between
the collar 42 and the land 40. The O-ring 44 is received in an
annular ring 46 machined into the body of the housing sub-assembly
30.
[0040] The seal provided by the O-ring 44 prevents leakage of
reagent into the compartment 36 between the land 40 of the housing
sub-assembly 30 and the collar 42 of the pump housing 14.
[0041] The end of the housing sub-assembly 30 remote from the
outlet end 18 comprises a connection block 50 of generally cuboidal
shape. A top face of the connection block 50 is provided with a
reagent inlet port 52 that receives a tubular reagent inlet
connector 54. The inlet connector 54 extends radially with respect
to the pump axis A and is connected to a reagent supply line (not
shown) in use.
[0042] A filter 55 is located in the flow path between the inlet
connector 54 and the reagent inlet 22 of the pump 12. In this
embodiment, the filter 55 is received in the inlet port 54. The
filter 55 is conveniently a disc filter, arranged to prevent
particulate contaminants in the reagent, such as urea crystals,
from entering the pump 12.
[0043] The connection block 50 is also provided with a drilling 56
to admit an electrical connector 58. The electrical connector 58
connects with the electrical connection point 26 of the pump 12. A
further O-ring 60 is provided to seal the electrical connector 58
in the drilling 56. The O-ring 60 is again provided in an annular
groove 62 provided in the body of the housing sub-assembly.
[0044] FIG. 2 shows a pump assembly 100 in accordance with an
embodiment of the present invention. Like features between FIGS. 1
and 2 are referred to with reference to the same reference
numerals
[0045] The pump assembly 100 of FIG. 2 comprises a pump
sub-assembly 12 contained within a water cooled housing
sub-assembly 30.
[0046] The pump sub-assembly 12 comprises an over-moulding member
102 and a solenoid actuator 103, the solenoid actuator 103
comprising: an actuator core (also referred to as pump core or
inner pole piece) 104, an outer pole piece 106, a magnetic sleeve
107, a bobbin 108 and a solenoid coil 110, the solenoid coil being
carried on the bobbin. The components of the actuator are, in turn,
supported by the over-moulding member. A pumping region 112 within
the pump sub-assembly 12 is provided by a volume defined by the
outer pole piece 106, a back plate member 114 and a top face 115 of
the actuator core 104. A bore 116 is provided within the actuator
core 104. At the end of the bore remote from the pumping region 112
is a pumping chamber region 118.
[0047] The housing sub-assembly 30 comprises a cavity 120 for
receiving the pump sub-assembly 12, the cavity being dimensioned
such that a compartment 122 is defined between the housing 30 and
pump 12 sub-assemblies in the general region of the solenoid
actuator 103. In use, a coolant, e.g. water, is supplied via a
hydraulic connector (not shown in FIG. 2) to the compartment 3 to
provide water cooling of the actuator.
[0048] The housing sub-assembly 12 comprises a reagent inlet port
52 wherein a reagent connector (not shown) can be interfaced with
the housing sub-assembly 30 in order to supply a reagent, e.g.
Adblue reagent.
[0049] The pump sub-assembly 12 further comprises a neck portion
124 remote from the solenoid actuator, the neck portion being
dimensioned to be received within a drilling 126 in the body of
housing sub-assembly 30. The neck portion 124 in turn comprises a
bore 128 that is coincident with the pump assembly axis A. In use,
the bore 128 receives an electrical connector cable 58 for
connection to terminals of the solenoid coil wire 110.
[0050] The reagent flows from the inlet port 52 through a second
drilling 130 in the housing sub-assembly 30 to a radial gallery 132
defined between the housing sub-assembly 30 and the neck portion
124 of the pump sub-assembly 12. The gallery 132 permits assembly
of the pump sub-assembly into the housing sub-assembly and also
allows orientation of the pump sub-assembly relative to the housing
sub-assembly during this process.
[0051] The reagent gallery 132 is sealed from the outside
environment in the region of the neck portion 124 by two O ring
seals (134, 136) and sealed from the main housing water chamber 122
via a third O ring seal 138, all of which are retained by suitable
O Ring grooves 140 moulded as part of the coil over-moulding member
102. Although, two O rings are shown (134, 136) in the neck portion
124 of the pump sub-assembly, it is noted that a single O ring seal
would be sufficient for this primary function.
[0052] From the gallery 132, reagent is then routed through the
coil over-moulding member 102 via a number of flow ports 142, one
of which is visible in FIG. 2. It is however noted that three or
four ports could be provided equispaced around the axis A to
provide efficient fluid communication between the gallery 132 and
the internal pumping region 112 of the pump sub-assembly 12.
[0053] As reagent exits the flow port 142 it then passes through a
drilling 144 in the non magnetic plunger back stop plate 114 before
entering the pumping region 112. With the reagent delivered to the
pumping zone 112, the flow path resumes the route as described in
EP1878920. Note that the drilling 144 may be a port that is drilled
or manufactured by other means (e.g. produced by stamping/fine
blanking etc.).
[0054] It is noted that the drilling 144 in the back plate 114 is
arranged during assembly to line up with the port 142 in the
over-moulding member 102. In the event of multiple ports 142 the
back stop plate would comprise an equal number of drillings 144 in
the same orientation as the ports 142.
[0055] The over-moulding member 102 is formed via an injection
moulding method. One potential method for manufacturing the ports
and aligning them with the drillings 144 of the back stop plate 114
would be to align the drillings 144 of the back plate 114 with the
removable cores of a mould tool when injection moulding the
over-moulding member 102. Alignment is important as it permits the
routing of the solenoid coil cable 58 to the coil wire terminals
(not shown) which would need to pass within (in between) the gaps
of the reagent ports 142.
[0056] To allow the assembly of the plunger back stop accurately
and for the solenoid to operate correctly the magnetic outer pole
piece 106 and magnetic outer sleeve 107 are formed from one deep
drawn component, which also incorporates a locating face 146 and
crimp feature 148 for the pump core 104. Forming the outer pole
piece 106 and magnetic outer sleeve 107 via a deep draw process
reduces material waste compared to a process where the components
are formed by machining.
[0057] The pump sub-assembly 12 may therefore be assembled by
winding the coil wire 110 around the coil former or bobbin 108. The
wound coil former (110, 108) can then be slid into the magnetic
drawn component 107, which will have a slot (not shown in this
view) to receive the bobbin terminals. Then with the back plate 114
in place, and flow port 142 cores aligned to the back plate ports
144 over moulding will take place over the whole pump sub-assembly
12. Holes 150 in the magnetic outer sleeve 107 permit filling of
the volume 152 between the coil windings 110 and the outer sleeve
inside face 107.
[0058] The axial positioning of the coil wire 58 allows the water
cooled cavity 122 within the housing to be optimized and sized
primarily for the purposes of cooling. The overall outside diameter
of the housing sub-assembly 30 may therefore be reduced.
[0059] As noted above, the pumping mechanism of the pump
sub-assembly is known from, for example EP-A-1878920. Briefly
however, a supply passage 154 is defined by an annular cavity
between the coil former 108 and the actuator core 104. A plurality
of filling ports 156 (of which one is shown in FIG. 2) comprising a
radial through bore, extend from the axial bore 116 to the supply
passage 154.
[0060] A reciprocating pumping element, such as a plunger or piston
(not shown in FIG. 2) is slidably accommodated within the bore 116.
A disc-shaped armature (also not shown in FIG. 2) is attached to
the plunger.
[0061] In order to dispense reagent, a current is passed through
the solenoid coil 110 to energise the coil and induce a magnetic
field around the coil. The resulting magnetic field exerts a force
on the armature which, in turn, drives a pumping stroke of the
plunger. By means of the reciprocating plunger reagent is pumped
from the internal pumping region 112 via the passage 154 and ports
156 to the pumping chamber 118 and then out to an adjoining nozzle
tube (not shown in FIG. 2). A further seal member 158 is provided
between the coil former 108 and actuator core 104.
[0062] Further variations and modifications not explicitly
described above may also be contemplated without departing from the
scope of the invention as defined in the appended claims.
* * * * *