Fluid operated damper with nonreleasable cover unit for electromagnetic value

A fluid oscillation damper is provided with an electromagnetically controlled valve for varying the damping force of the oscillation damper. The electromagnetically controlled valve is housed within a compartment confined by two housing parts. A first housing part is fastened to a container of the oscillation damper. A second housing part is fastened to the first housing part. Both housing parts are nonreleasably interconnected.

BACKGROUND OF THE INVENTION 
In modern motor cars hydraulic oscillation dampers are provided which 
permit variation of the damping behaviour. Such hydraulic oscillation 
dampers are provided with an electromagnetically controlled valve unit. 
This valve unit is provided in a flow path connecting two working chambers 
the volume of which is altered in opposite senses during movement of a 
piston rod with respect to the container of the respective oscillation 
damper. This flow path is in parallel with a continuously open throttled 
flow path. By variation of the cross-sectional area of the flow path 
through the electromagnetically controlled valve unit, the damping 
behaviour of the oscillation damper can be varied. The variation of the 
damping behaviour may be a continuous or a step-wise variation. The 
electromagnetically controlled valve unit is preferably fastened to the 
outer side of a container of the oscillation damper. Electromagnetic and 
fluidic components of the valve unit are accommodated within a compartment 
attached to the outer side of the container. 
STATEMENT OF THE PRIOR ART 
According to German patent publication DE-OS 40 24 920 a tubular basic 
housing unit is mounted to the external side of the container of an 
oscillation damper. A cover unit is fastened to the free end of the basic 
housing unit. For the connection of the cover unit an interconnecting 
sleeve is used. This interconnecting sleeve is axially movable along the 
tubular basic housing unit against an abutment ring fixed in a 
circumferential groove of the tubular basic housing unit. The 
interconnecting sleeve is provided with internal thread means which can be 
screwed onto external thread means of the cover unit until the 
interconnecting sleeve abuts the abutment ring. Such, the cover unit may 
be pressed into sealing engagement with the basic housing unit. 
It is to be noted that the German publication DE-OS 40 24 920 is commonly 
owned with the present application. 
The above-mentioned older construction has two drawbacks: 
On the one hand, the interconnecting sleeve can be released by any 
hobbyist, and it cannot be expected that the necessary torque is applied 
when reassembling the cover unit and the basic housing unit by screwing 
the interconnecting sleeve with respect to the cover unit. Such, the 
expected tightness cannot be guaranteed after reassembling. Inadequate 
tightness may lead to a reduction in damping power owing to the loss of 
the damping medium within the valve unit. 
A further drawback comes up, when pressurized gas is contained within the 
oscillation damper. In this case, the gas pressure may be reduced when 
dissembling the cover unit and the housing unit. A reduction of the gas 
pressure leads to the risk of foaming of a liquid within the oscillation 
damper during operation. For the hobbyist or other unauthorized person it 
is scarcely possibly to establish gas pressure again within the 
oscillation damper after reassembling the cover unit and the basic housing 
unit. 
A further disadvantage may occur with the above-mentioned construction, 
when by the connection of the cover unit and the basic housing unit a 
ferromagnetic flange portion is located inside the compartment confined by 
the basic housing unit and the cover unit. In such a construction the 
loosening of the connection between the basic housing unit and the cover 
unit and the reassembling of these units after a preceding disassembling 
can lead to a wrong positioning of components within the compartment. E. 
g. the abutment faces for biasing springs may be wrongly located so that 
the respective biasing forces are wrongly adjusted and the damping power 
is different from the expected damping power. So it may occur that the 
expected hardest damping characteristic cannot be selected. 
OBJECT OF THE INVENTION 
It is an object of the present invention to provide an electromagnetically 
controlled valve unit for a fluid operated oscillation damper, in which 
the safety level is increased by making a disassembly of the housing units 
confining the electro-magnetic and fluidic components impossible or at 
least very difficult so that misadjustment of the housing units and of the 
electromagnetic and fluidic components contained therein is avoided. 
A further object is to obtain a simplified design and to allow simple 
assembling methods. 
A further object of the invention is to warrant the tightness of the 
compartment confining the electromagnetic and fluidic components. 
A further object is to prevent hobbyists, amateurs and other unauthorized 
people from access to the electromagnetic and fluidic components inside 
the compartment, such as to prevent unauthorized modification of the 
damping characteristics of the oscillation damper. 
SUMMARY OF THE INVENTION 
In consideration of at least a part of the above-mentioned objects the 
invention provides a fluid operated oscillation damper with an 
electromagnetically controlled valve unit for varying the damping force of 
the oscillation damper. The valve unit comprises a plurality of fluidic 
and electromagnetic valve unit components. At least a part of these 
fluidic and electromagnetic valve unit components are accommodated within 
a valve unit compartment of the oscillation damper. The valve unit 
compartment is confined by compartment confining means. These compartment 
confining means comprise at least two housing units. One of the housing 
units is a basic housing unit attached to a part of the oscillation 
damper. A further one of the housing units is a cover unit attached to the 
basic housing unit. The cover unit is nonreleasably connected by 
nonreleasable connection means to the basic housing unit. 
By the term "fluid operated oscillation damper" hydraulic, pneumatic and 
hydropneumatic oscillation dampers are included. Preferably, the damping 
force is generated by a hydraulic medium flowing through throttled 
passages. Correspondingly, the term "fluidic valve unit components" is to 
comprise all valve components which control flow of hydraulic or pneumatic 
medium. 
By the nonreleasable connection of the housing units a nonauthorized person 
is prevented to disassemble the housing units and the electromagnetic and 
fluidic valve unit components accommodated therein. Moreover, the sealing 
measures provided by the manufacturer cannot be damaged by unauthorized 
persons. Moreover, a damping power adjustment can no longer be manipulated 
by unauthorized persons. 
The cover unit may be connected to the basic housing unit by positively 
interengaging locking means. These positively interengaging locking means 
can be obtained by plastic deformation of the respective materials of the 
housing unit at the location of engagement. These materials may comprise 
combinations of metal-metal, plastics material-plastics material or 
metal-plastics material. 
According to a first embodiment the basic housing unit and the cover unit 
have respective sleeve-shaped portions overlapping each other in an axial 
direction along a common axis. These sleeve-shaped portions are connected 
with each other. One of these sleeve-shaped portions is a radially inner 
sleeve-shaped portion, and the other one of these sleeve-shaped portions 
is a radially outer sleeve-shaped portion. 
In case of such an arrangement of a radially inner sleeve-shaped portion 
and a radially outer sleeve-shaped portion the radially inner 
sleeve-shaped portion may be provided with a circumferential groove within 
a radially outer surface thereof, and the radially outer sleeve-shaped 
portion may be provided with a radially inward displaced circumferential 
bead engaged into said circumferential groove. The circumferential groove 
may be preshaped before combining the sleeve-shaped portions such that the 
material of the radially outer sleeve-shaped portion may then be 
dislocated radially inwards into the preshaped groove such as to form the 
circumferential bead. Alternatively, it is also possible to preassemble 
the sleeves before shaping the circumferential groove and to thereafter 
provide the circumferential groove simultaneously with shaping the 
circumferential bead. When talking of a circumferential groove, this term 
should include a continuous circumferential groove as well as a circular 
series of individual depressions. Moreover, the term "circumferential 
bead" should also cover both a continuous bead and a circular arrangement 
of individual, radially inwardly directed projections obtained by 
deformation of the radially outer sleeve at the respective locations. 
It is also possible that the radially inner sleeve-shaped portion is 
provided with radially outward directed locking flange means and that the 
radially outer sleeve-shaped portion is provided with radially inward 
directed locking flange means bent behind the radially outward directed 
locking flange means. At least one of the radially outward directed 
locking flange means and the radially inward directed locking flange means 
may be circumferentially continuous locking flange means. Alternatively, 
one or both flange means may be provided by respective series of flange 
forming sections separated from each other in circumferential direction by 
respective gaps. 
It is further possible that the radially inner sleeve-shaped portion and 
the radially outer sleeve-shaped portion are locked to each other by a 
locking ring located radially between a radially outer circumferential 
face of the radially inner sleeve-shaped portion and a radially inner 
circumferential face of the radially outer sleeve-shaped portion. The 
locking ring may be embossed into both the radially inner and the radially 
outer circumferential face. During the connecting phase one may position 
the locking ring between a smooth radially outer circumferential face and 
a smooth radially inner circumferential face and exert radial pressure 
onto the radially outer sleeve portion such as to simultaneously emboss 
the locking ring into both adjacent circumferential faces. Alternatively, 
it is also possible to preshape a groove in the radially outer face,to 
insert the locking ring therein, to assemble the radially inner and the 
radially outer sleeve portion with the locking ring being located between 
the respective radially outer and radially inner circumferential faces and 
to thereafter urge the material of the radially outer sleeve portion 
towards the radially inner sleeve portion on both axial sides of the 
locking ring. 
Preferably, the radially inner sleeve-shaped portion is a part of the basic 
housing unit, while the radially outer sleeve-shaped portion is a part of 
the cover unit. This is due to the fact that normally the materially of 
the basic housing unit is a relatively thick metallic tube material which 
can easily resist the pressure for obtaining the connection. 
According to a still further embodiment the basic housing unit and the 
cover unit have respective radially outer circumferential faces 
circumferentially extending about a substantially common axis and axially 
adjacent each other and both said circumferential faces of the basic 
housing unit and of the cover unit are axially overlapped by an 
interconnecting sleeve. This interconnecting sleeve is in locking 
engagement with both circumferential faces of the basic housing unit and 
the cover unit, respectively. In such case, the interconnecting sleeve may 
be locked to at least one of the radially outer circumferential faces by a 
ring member effecting a locking engagement in at least one axial 
direction. Locking engagement "in at least one axial direction" means that 
the interconnecting sleeve is movable with respect to said one 
circumferential face in axial direction unit1 abutting a respective 
abutment face provided on said on circumferential face. 
Further, the interconnecting sleeve may be locked to at least one of the 
radially outer circumferential faces by a circumferential radially inward 
directed locking bead engaging into a circumferential locking groove 
provided in said radially outer circumferential surface. 
Preferably, one may combine the two alternatives such that the 
interconnecting sleeve is shaped for entering into the abutting engagement 
with abutment means of a first one of the circumferential faces when being 
brought in overlapping condition with respect to the other one of the 
radially outer circumferential faces during an assembling phase and that 
hereupon, the locking bead is generated on the interconnecting sleeve such 
as to enter into the locking groove. The above-mentioned alternatives for 
providing the locking groove (preshaping or simultaneous shaping with the 
shaping of the locking bead) may again be applied. Both the locking groove 
and the locking bead may again be continuous or constituted by individual 
depressions and projections, respectively, in circular arrangement. 
Sealing means may be provided between the basic housing unit and the cover 
unit. These sealing means may be maintained under sealing pressure by the 
nonreleasable connection means. 
The basic housing unit may have a tubular shape and may be fastened by one 
of its ends to a container tube member of the oscillation damper. The 
other end of the tubular basic housing unit may then be connected to the 
cover unit. The tubular basic housing unit may e. g. be fastened to the 
outer circumferential face of the container tube member by welding, such 
as to have its axis intersecting the axis of the container tube member 
with a substantially 90.degree. angle. Preferably, the basic housing unit 
is connected to the container tube member before being assembled with and 
connected to the cover unit. After connecting the basic housing unit to 
the container tube member the cover unit is connected thereto. The 
electromagnetic and fluidic components as defined above may be inserted 
into the basic housing unit or/and into the cover unit before assembling 
the cover unit and the basic housing unit. 
The cover unit may be partially made of metallic material or ferromagnetic 
material and partially made of plastics material. The nonreleasable 
connecting means are preferably provided between the basic housing unit 
and metallic material of the cover unit. The cover unit may be obtained by 
a injection moulding process in which the preshaped metallic material is 
inserted into an injection mould during the injection phase. 
If the basic housing unit and the cover unit have a common axis, one may 
accommodate within the cover unit an annular electromagnetic coil around 
the axis and an axially movable armature member inside a central space 
surrounded by the annular electromagnetic coil. 
For providing a strong magnetic field acting onto the armature and 
concentrating the field in the area of the armature with the field lines 
being directed in axial direction at the location of the armature, one may 
provide ferromagnetic core means toroidally extending around the annular 
electromagnetic coil. These ferromagnetic core means may comprise a 
ferromagnetic flange portion provided axially between the annular 
electromagnetic coil and the basic housing unit. This ferromagnetic flange 
portion may be an iron-made flange portion. The electromagnetic flange 
portion represents a relatively rigid structural part which may also be 
used for stiffening at least one of the basic housing unit and the cover 
unit in radial direction. This is particularly true, if the ferromagnetic 
flange portion fully fills the respective internal cross-sectional area of 
the basic housing unit or/and the cover unit. It is, therefore, most 
desirable that the nonreleasable connecting means or at least part of them 
are provided at or axially adjacent the ferromagnetic flange portion. 
Thus, reshaping operations by radial pressure onto the radially outer side 
of the cover unit or/and the basic housing unit may be made in areas 
stiffened by the ferromagnetic flange portion, and undesirable 
deformations of the cover unit or/and the basic housing unit are avoided. 
The ferromagnetic core means may further comprise a ferromagnetic jacket 
surrounding the annular electromagnetic coil and integral with a 
ferromagnetic end wall adjacent an end face of the annular electromagnetic 
coil remote from the ferromagnetic flange portion. This ferromagnetic 
jacket may provide a portion of the cover unit nonreleasably connected to 
the basic housing unit. 
Preferably, the ferromagnetic end wall has a central opening axially 
aligned with the central space of the annular coil. Then, a central 
ferromagnetic core member may be located inside the central opening and 
extend into the central space. The central opening may be closed by a 
plastics material layer of the cover unit. This plastics material layer 
may cover the ferromagnetic end wall and part of the ferromagnetic jacket. 
The plastics material layer of the cover unit may extend through openings 
of the ferromagnetic jacket and be integral with a plastics material 
jacket surrounding the annular electromagnetic coil on a radially outer 
circumferential side thereof. In case of injection moulding the 
ferromagnetic jacket and the electromagnetic coil are inserted into the 
injection mould, possibly in combination with further internal components. 
The ferromagnetic flange portion may be in axial engagement with a 
substantially axially directed engagement face of the ferromagnetic 
jacket. Thus, a correct relative positioning of the ferromagnetic flange 
portion and the ferromagnetic jacket is obtained and simultaneously, the 
subassembly comprising the ferromagnetic flange portion and the 
ferromagnetic jacket may be radially or/and axially positioned with 
respect to one of the basic housing unit and the cover unit. Moreover, the 
cover unit may be correctly positioned with respect to the basic housing 
unit through the ferromagnetic flange portion or/and the ferromagnetic 
jacket. 
The ferromagnetic flange portion may be maintained in axial engagement with 
the engagement face by the nonreleasable connecting means. Such, the 
magnetic circuit is positively closed at the interface between the 
ferromagnetic flange portion and the ferromagnetic jacket. 
The ferromagnetic flange portion may further be axially supported by a 
valve components housing which as again axially supported by and inside 
the basic housing unit and open towards the central space such as to 
expose the valve components inside the valve components housing to the 
armature member. 
Sealing means may be provided for sealing the valve components housing with 
respect to the ferromagnetic flange portion and the basic housing unit. 
These sealing means may be maintained under sealing pressure by the 
non-releasable connection means. 
The plastics material jacket may form together with a radially outward open 
coil carrier a coil housing for the annular electromagnetic coil. 
The cover unit may be provided with pretension application means permitting 
pretensioning of the cover unit towards the basic housing unit before and 
during connecting the cover unit to the basic housing unit. Such, a 
pretensioning device may be applied to the cover member, on the one hand, 
and to the oscillation damper, on the other hand, for pretensioning the 
cover unit and the basic housing unit toward each other. 
Moreover, the basic housing unit may be combined with further pretension 
application means. In this case, the pretension may be applied to the 
basic housing unit and to the cover unit without loading the container 
member of the oscillation damper by pretensioning forces. 
Both the cover unit and the interconnecting sleeve may be provided with 
pretension application means permitting pretensioning of the cover unit 
towards the basic housing unit after having locked said interconnecting 
sleeve to the radially outer face of the basic housing unit and before 
locking it to the radially outer surface of the cover unit. This is a 
preferred embodiment because no reshaping forces act onto the basic 
housing unit when making the nonreleasable connection. 
The invention further concerns a method for assembling a fluid operated 
oscillation damper with an electromagnetically controlled valve unit of 
the above described type. 
This method comprises fastening the basic housing unit to a part of the 
oscillation damper, inserting the electromagnetic and fluidic valve unit 
components into at least one of the basic housing unit and the cover unit, 
pretensioning the cover unit towards the basic housing unit and 
nonreleasably connecting the cover unit to the basic housing unit while 
maintaining pretension between them. The radial deformation of the 
respective housing portions for providing the connection means may be 
obtained by conventional rolling or caulking. 
The fluid pressure forces occurring within the compartment may be 
positively transmitted to the basic housing unit. E. g., fluid pressure 
forces may be transmitted to the ferromagnetic flange portion, from the 
ferromagnetic flange portion to the cover unit and from the cover unit to 
the basic housing unit through the connection means. The connection means 
are such that they can be easily obtained in the manufacturing plants. 
They cannot be opened and reclosed by an unauthorized person. In case of 
need of repair the manufacturer or other authorized persons can, 
nevertheless, easily release the connection means and apply them again 
after repair such that no damaging of the internal electromagnetic and 
fluidic components is to be expected, more particularly, damaging to the 
magnetic coil, the casing thereof and the armature is avoided. 
The various features of novelty which characterize the invention are 
pointed out with particularity in the claims annexed to and forming a part 
of the disclosure. For a better understanding of the invention, its 
operating advantages and specific objects attained by its use, reference 
should be had to the accompanying drawings and descriptive matter in which 
there are illustrated and described preferred embodiments of the invention 
.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
FIG. 1 shows a complete oscillation damper 1, a detailed illustration of 
the valve unit 3 being omitted for the sake of clarity. The oscillation 
damper 1 consists essentially of a pressure pipe 5 in which a piston 7 on 
a piston rod 9 divides a working space 11 into an upper or piston-rod-side 
working chamber 11a and a lower or piston-rod-remote working chamber 11b. 
A bottom valve unit 15 closes the pressure pipe 5 at the lower end 
thereof. A fluid path 19 is formed between the pressure pipe 5 and an 
intermediate pipe 17, said intermediate pipe 17 being arranged 
concentrically with respect to the pressure pipe 5. A connecting orifice 
21 in the pressure pipe 5 connects the upper working chamber 11a with the 
fluid path 19. A compensating chamber 25 is confined between the 
intermediate pipe 17 and a portion of the pressure pipe 5, on the one 
hand, and a container pipe 23, on the other hand. This compensating 
chamber 25 is axially limited by a base member 27 and a piston rod guiding 
and sealing unit 29. The working space 11 is separated by the piston 7 
into the upper working chamber 11a and the lower working chamber 11b. Both 
the upper and the lower working chamber are filled with a liquid. The 
compensating chamber 25 is also filled with damping liquid up to the level 
L and contains a possibly pressurized gas above the level L. The bottom 
valve unit 15 provides communication between the working chamber 11b and 
the compensating chamber 25. The piston 7 provides communication between 
the lower working chamber 11b and the upper working chamber 11a. According 
to an illustrative example the oscillation damper works as follows: When 
the piston rod 9 moves upwards, a high flow resistance occurs across the 
piston 7 and a high pressure is generated in the upper working chamber 
11a. Liquid from the upper working chamber 11a flows through said high 
flow resistance into the lower working chamber 11b. As the piston rod 9 
moves outward of the working space 11, the available volume within the 
working space 11 is increased. Therefore, liquid can flow from the 
compensating chamber 25 through the bottom valve unit 15 into the lower 
working chamber 11b. The flow resistance through the bottom valve unit 15 
is small in this phase of operation. The movement of the piston rod 9 with 
respect to the pressure pipe 5 is damped. 
On inward movement of the piston rod 9 fluid flows from the lower working 
chamber 11b through the piston 7 into the upper working chamber 11a. The 
flow resistance across the piston 7 is relatively small and the flow 
resistance across the bottom valve unit 15 is relatively large. Therefore, 
a considerable pressure exists even within the upper working chamber 11a. 
The volume within the working space 11 is reduced by the piston rod 9 
entering into the working space 11. Thus, damping liquid must flow from 
the lower working chamber 11b through the bottom valve unit 15 into the 
compensating chamber 25. In this phase of operation the flow resistance 
through the bottom valve unit 15 is high such that a high pressure occurs 
within the lower working chamber 11b and also within the upper working 
chamber 11a. 
By the connecting orifice 21 and the fluid path 19 the upper working 
chamber 11a is connected with the compensating chamber 25 via the valve 
unit 3. This is shown in more detail in FIG. 2, which will be described 
later. As long as the valve unit 3 is closed, the bypass established by 
the connecting orifice 21, the fluid path 19 and the valve unit 3 is also 
closed. This is the hardest mode of operation of the oscillation damper. 
When, however, the valve unit 3 is more or less opened, the bypass is also 
open. As a result thereof the following behaviour exists: On upward 
movement of the piston rod 9 liquid can flow from the highly pressurized 
upper working chamber 11a not only across the piston 7 providing a high 
flow resistance but also from the working chamber 11a through the bypass 
21,19,3 to the compensating chamber 25. Such, the damping force is 
reduced. 
When the piston rod 9 moves downwards, there exists again a high pressure 
within the upper working chamber 11a, as described above. Therefore, 
damping liquid can flow from the upper working chamber 11a through the 
bypass 21,19,3 to the compensating chamber 25. This means that the damping 
liquid which must be expelled from the working space 11 as a result of the 
reduced volume therein does not only escape through the bottom valve unit 
15 to the compensating chamber 25 but can also partially escape through 
the bypass 21,19,3 to the compensating chamber 25. Such, the damping force 
is again reduced by the open bypass 21,19,3. It is to be noted that the 
direction of flow of the damping liquid through the bypass 21,19,3 is the 
same, both on upward movement and downward movement of the piston rod 9 
with respect to the pressure pipe 5. By increasingly closing the flow 
resistance through the valve unit 3 the damping force can be increased 
both for upward and downward movement of the piston rod 9, and by 
increasingly opening the valve unit 3 the damping force can be reduced 
both for upward movement and downward movement of the piston rod 9. It is 
possible to selectively open and close the valve unit or to continuously 
vary the flow resistance through the valve unit 3. 
In FIG. 2 one can again see the fluid path 19 and the compensating chamber 
25, which are interconnectable through the valve unit 3 with cable 39b. 
The fluid path 19 is connected to the upper working chamber 11a as shown 
in FIG. 1. The flow direction from the fluid path 19 to the compensating 
chamber 25 across the valve unit 3 is indicated in FIG. 2 by the dotted 
line D provided with arrows indicating the flow direction both for inward 
movement and outward movement of the piston rod 9 with respect to the 
pressure pipe 5. One can see in FIG. 2 a valve member V which can be 
lifted with respect to a valve seat S, such as to open the flow path D 
from the fluid path 19 to the compensating chamber 25 For more details as 
to the function of the valve unit 3 it is referred to the above-mentioned 
German publication DE-OS 40 24 920A1 published on 13 Feb. 1992, to the 
corresponding U.S. patent application 07/738 155 filed on 30 Jul. 1991, 
from which the following U.S. patent applications were continuations: Ser. 
No. 08/071,994 now abandoned; Ser. No. 08/157,837now abandoned; and Ser. 
No. 08/238,806. 
Reference is also made to the corresponding British Publication GB 22 47 
933A published on 18 March 1992. For explaining the principles of the 
present invention it is sufficient to say that the valve member V is urged 
downward in the closing sense towards the valve seat S by a helical 
compression spring H and that the valve member V can be lifted in response 
to upward movement of an electromagnetic armature member A. This armature 
member A is biased in downward direction by a helical compression spring G 
and can be lifted by energization of a magnetic coil 39 which is energized 
through a current supply cable 39b. Further details of the construction 
and operation can be taken from the above-mentioned specifications. 
The valve unit 3 comprises a housing 70. This housing 70 is composed by a 
basic housing tube 31 and a cover unit 71. The basic housing tube 31 is 
welded at 72 to the container pipe 23. The cover unit 71 is fastened to 
the basic housing tube 31. 
A pot-shaped valve components housing 33 is inserted into the basic housing 
tube 31 and is axially located on a shoulder face 51 inside the basic 
housing tube 31. Various valve components are located inside the valve 
components housing 33. The lower end of the valve components housing 33 is 
shaped as a tube section 33a, which provides the valve seat S and is 
sealingly connected to the fluid path 19. 
The cover unit 71 comprises an iron jacket 43 integral with an iron end 
wall 43a. The iron jacket 43 and the iron end wall 43a are coated with a 
plastic layer 41. An annular electromagnetic coil 39 is housed within the 
iron jacket 43. This electromagnetic coil 39 is carried by a coil carrier 
39a, which is annular about an axis X and is open in radial outward 
direction. The coil carrier 39a is closed in radially outward direction by 
a plastics material 41a integral with the plastic layer 41 through 
openings 43b of the iron jacket The plastics layer 41 and the plastics 
material 41a are integrally moulded by injection moulding with the iron 
jacket 43, the iron end wall 43a integral therewith and the 
electromagnetic coil 39 and the coil carrier 39a being inserted into the 
injection mould. 
A ferromagnetic core 44 is inserted into a central opening of the iron end 
wall 43a and covered by the plastics layer 41. An iron flange portion 37 
is provided at the lower side of the electromagnetic coil 39 and is 
engaged with a shoulder face 47 of the iron jacket 43. A pole tube 42 is 
seated within an annular recess 42a of the iron flange portion 37. The 
pole tube 42 is sealingly connected to the iron flange portion 37 and to 
the ferromagnetic core 44. The armature A is guided within the pole tube 
42. The pole tube 42 is made of nonmagnetic material so that the magnetic 
field lines are deflected by the lower end of the pole tube 42. The iron 
jacket 43, the iron end wall 43a, the ferromagnetic core 44 and the iron 
flance portion 37 form a ferromagnetic core arrangement which toroidally 
surrounds the electromagnetic coil 39. 
The cover unit 71 is fastened to the basic housing tube 31 by a 
sleeve-shaped extension 43c of the iron jacket This sleeve-shaped 
extension 43c axially overlaps the basic housing tube 31. The 
sleeve-shaped extension 43c is fastened to the basic housing tube 31 by a 
circumferential bead 55 being embossed into a circumferential groove 49 on 
the radially outer face of the basic housing tube 31. The iron jacket 43 
is provided with a pretensioning flange 45. The pretensioning flance 45 
offers a pretension face 53. The cover unit 71 can be pretensioned in 
downward direction as shown in FIG. 2 toward the basic housing tube 31 by 
a pretensioning tool engaging the container pipe 23, on the one hand, and 
the pretensioning face 53, on the other hand. Such, the iron flange 
portion 37 is pressed against the upper end of the valve components 
housing 33, the valve components housing 33 is engaged with the shoulder 
face 51 of the basic housing tube 31, and the iron flange portion 37 is 
engaged with the shoulder face 47 of the iron jacket 43. The helical 
compression spring H is compressed between the iron flange portion 37 and 
the valve member V, which is seated on the valve seat S. 
While maintaining this pretension of the cover unit 71 against the basic 
housing tube 31, the bead 55 is rolled or caulked into the circumferential 
groove of the basic housing tube 31 so that after removing the 
pretensioning tool an internal pretension is maintained. A sealing ring 76 
is, therefore, maintained in sealing engagement with the valve components 
housing 33, the iron flange portion 37 and the basic housing tube 31. 
Such, the compartment C confined by the basic housing tube 31 and the 
cover unit 71 is sealed against atmosphere. All components of the valve 
unit 3 are positioned with respect to each other, and the helical 
compression spring H as well as the helical compression spring G and 
further springs are biased to the desired degree. 
It is to be noted that the upper end of the basic housing tube 31 is 
radially engaged at 77 with the iron flange portion 37 such that when 
rolling or caulking the bead 55 into the groove 49, no deformation of the 
basic housing tube 31 and of the iron jacket 43 can occur. 
The electromagnetic coil 39 is completely separated from the liquid within 
the compartment C by the iron flange portion 37. The pretension during 
connecting the cover unit 71 and the basic housing tube 32 is selected 
such that no play can occur 
The embodiment of FIG. 3 is very similar to the embodiment of FIG. 2. 
Analogous parts are designated by the same reference numerals as in FIG. 2 
increased by 100. The only difference between the embodiment of FIG. 3 and 
FIG. 2 lies in the connection between the cover unit 171 and the basic 
housing tube 131. The basic housing tube 131 is provided with a radially 
outwardly directed flange 178. The extension 143c of the iron jacket 143 
is radially inwardly flanged below the radially outwardly directed flange 
178 for providing the connection between the cover unit 171 and the basic 
housing tube 131. The radially outwardly directed flange 178 is obtained 
by providing an external circumferential groove 179 into the outer 
circumferential face of the basic housing tube 131. The inward flanging of 
the flange 143d is again made by rolling or caulking, while the cover unit 
171 is pretensioned against the basic housing tube 131. It is to be noted 
that during this flanging operation at 143d, the upper end of the basic 
housing tube 131 is again radially supported at 177 by the iron flange 
portion 137. It is further to be noted that the radially inner end 157 of 
the flange 143d is spaced from the base surface 159 of the groove 179 for 
avoiding any misalignment. 
In all other details the construction and the assembling corresponds to the 
embodiment of FIG. 2. 
A third embodiment is shown in FIG. 4. This embodiment is again very 
similar to the embodiment of FIGS. 1 and 2. Analogous parts are designated 
by the same reference numbers increased by 200. In the embodiment of FIG. 
4 the iron jacket 243 is again provided with an extension 243c extending 
around the basic housing tube 231. A groove 249 is provided in the 
radially outer face of the basic housing tube 231. A locking ring 261 is 
inserted into the groove 249. The extension 243c of the iron jacket 243 is 
rolled or caulked onto the locking ring 261 for nonreleasably connecting 
the cover unit 241 to the basic housing tube 231. This is again made 
during maintaining a pretension between the cover unit 271 and the basic 
housing tube 231. The interengagement of the iron flange portion 237 with 
the iron jacket 243 again supports the extension 243c during the rolling 
or caulking operation. 
In the embodiment of FIG. 5 which is again similar to the embodiment of 
FIG. 2, analogous parts are designated by the same reference numbers 
increased by 300. In this embodiment an interconnecting sleeve 382 is 
provided by connecting the cover unit 371 with the basic housing tube 331. 
The interconnecting sleeve 382 is axially fixed in upward direction by an 
abutment ring 361, which is engaged by an upwardly open groove 383 of the 
interconnecting sleeve 382. The abutment ring 361 is inserted into a 
groove 349 provided in the external circumferential face of the basic 
housing tube 331. The interconnecting sleeve 382 overlaps the iron jacket 
343. The connection between the interconnecting sleeve 382 and the iron 
jacket 343 is obtained by shaping a circumferential bead 384 into a groove 
385 of the iron jacket 343 while maintaining an axial pretension between 
the pretension surface 353 and a further pretension surface 353' of the 
interconnecting sleeve 382. The basic housing tube 331 is free of radial 
and axial forces during assembling. The iron jacket 343 and the 
interconnecting sleeve 382 are supported by the iron flange portion 337, 
when the bead 384 is made by rolling or caulking. One can see in all 
embodiments that a tight engagement is provided between the ferromagnetic 
core 44, the iron end wall 43a, the iron jacket 43 and the iron flange 
portion 37, such as to obtain a closed magnetic circuit around the 
electromagnetic coil 39. The pole tube may be soldered to the 
ferromagnetic core 44 and to the iron flange portion 37. A separation of 
the cover unit 71 from the basic housing tube 31 results in the destroying 
of the valve unit 3. 
While specific embodiments of the invention have been shown and described 
in detail to illustrate the application of the inventive principles, it 
will be understood that the invention may be embodied otherwise without 
departing from such principles. 
The reference numerals in the claims are only used for facilitating the 
understanding and are by no means restrictive. 
The invention as described hereinabove in the context of the preferred 
embodiments is not to be taken as limited to all of the provided details 
thereof, since modifications and variations thereof may be made without 
departing from the spirit and scope of the invention.