Title of Invention

FLOAT FOR A FILL LEVEL SENSOR

Abstract The invention relates to a float (5) for a fill level sensor, comprised of a fuel-resistant plastic (7), an expanding means (8) and/or filler (9), whereby the expanding means consists of gas-filled plastic balls (11) that are provided in the form of microspheres (8), and the filler consists of micro-hollow balls (9). The microspheres (8) and the micro-hollow balls (9) are surrounded by fuel-resistant plastic (7).
Full Text PCT/EP2004/050810 - 1-
2003P08555WOUS
Description
Float for a fill level sensor
The subject of the invention is a float for a fill level
sensor, comprising a fuel-resistant plastic, an expanding means
and/or a filler. Floats of this type are used in fill level
sensors in fuel tanks of motor vehicles.
Floats made of fuel-resistant material are generally known. On
account of the low density of fuel, floats must have a
particularly low density. An additional difficulty is that,
for the most part, lever-type sensors are used as fill level
sensors. In the case of a fill level sensor formed as a lever-
type sensor, the float is fastened to a lever wire. Also
arranged on the lever wire is a sliding contact, which slides
over a resistor network. The float must consequently have a
much lower density than the fuel, since it has to compensate
not only for its own weight but also for the weight of the
lever wire. In the case of a fuel density of approximately
0.7 g/cm3, floats of this type must therefore have a density of
less than 0.5 g/cm3.
A material which is both fuel-resistant and has an adequately
low density is nitrophyl. Nitrophyl is a plastic containing
sulfur. The disadvantage of nitrophyl is its complex
production, which necessitates stringent requirements with
regard to environmental protection because of the sulfur
content.
Other known fuel-resistant materials are POM (polyoxymethylene)
and PA (polyamide). However, the production of foamed floats
from these materials is extremely complex. A further
disadvantage is that foaming produces an open-cell foam, the
cells of which are interconnected and therefore become flooded

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with fuel if the outer layer of the float is damaged. As a
result, the float loses its buoyancy, which leads to failure of
the fill level sensor.
It is also known to produce floats as hollow bodies from POM or
PA. These floats have the disadvantage that, when they are
used in a motor vehicle, the shell of the float can be damaged
as a result of the dynamics of the vehicle movement.The
leakage causes the float to be flooded, whereby it loses its
buoyancy, which leads to failure of the fill level sensor.
Floats comprising hollow bodies have therefore been unable to
become widely adopted as fill level sensors in motor vehicles.
The object of the invention is to provide a float for use in
fuels, with the intention that the float does not contain any
sulfur, is easy to produce and is resistant to dynamic loads.
The object is achieved according to the invention by the float
containing microspheres as an expanding agent, the microspheres
being gas-filled plastic balls.
Adding microspheres as an expanding agent allows a much smaller
amount to be admixed than in the case of other expanding
agents. The heating during production causes the plastic shell
to soften, so that the gas can make the plastic shell expand
and the volume of the microsphere increases by a factor of 40.
The plastic shell of the microspheres remains intact after the
expansion. The shells of the microspheres have the effect that
each cavity is self-contained, so that, even in the event of
the float becoming damaged, the cavities that are not affected
remain and ensure the buoyancy of the float.
The fuel-resistant plastic surrounds the microspheres and
reliably protects them from being attacked by the fuel. At the
same time, it has the necessary strength to be durable in
withstanding dynamic loads.

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On account of the high expansion factor of the microspheres,
more expensive starting materials can also be used both for the
fuel-resistant plastic and for the microspheres, since the
proportion of material contained in the float that is made up
by the microspheres and the fuel-resistant plastic is small on
account of the low density achieved. The float according to
the invention is therefore particularly inexpensive.
On account of the great expansion of the microspheres,
particularly low admixed amounts are sufficient to achieve a
low density of the float. It has been found that, to obtain a
proportion of approximately 85% of microspheres in the float,
it is sufficient for amounts of the order of 10% to be admixed
in the production process. Floats of this type have a density
of approximately 0.2 g/cm3. They are consequently ideally
suited for use in fuels. Depending on the place where they are
to be used, the density can be varied by the proportion of
microspheres in the float. Admixed amounts of microspheres
from 3% to 20% in the production process have been found to be
advantageous.
A low density of the float is achieved if the microspheres have
an average sphere diameter of from 3 0 m to 40 m, in
particular from 34 m to 38 m. In this case, the microspheres
retain their closed shell, so that the float is interspersed
with cavities that are self-contained and consequently
separated from one another.
The object is also achieved by the float containing micro
hollow balls as a filler. The micro hollow balls, based on
glass, likewise lead to a significant reduction in the density
on account of the cavities. Since micro hollow balls are much
less expensive than microspheres, particularly inexpensive
floats can be produced by using them.

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For a sufficiently low density of the float, micro hollow balls
with an apparent density of from 0.09 g/cm3 to 0.1 g/cm3 have
proven successful. The proportion of micro hollow balls may be
up to 98%. Float densities of less than 0.5 g/cm3 are achieved
with a proportion of micro hollow balls of over 70% in the
float.
Furthermore, the object is achieved by a float which contains
micro hollow balls and microspheres. The use of micro hollow
balls already leads to a reduction in the density, so that the
proportion of microspheres to achieve lower float densities can
be lowered. A float of this type can be produced particularly
inexpensively with a particularly low density.
The proportions of microspheres and micro hollow balls are
variable within wide limits, depending on the place where the
float is to be used. For instance, on account of the higher
density of diesel fuel of 0.4 g/cm3, floats for diesel fuel may
have a greater density than floats for gasoline. The amounts
of micro hollow balls that are admixed may vary between 3% and
60%, while the microspheres are added in a proportion of
between 3% and 20% during the production process. Good
processing of the starting materials by means of injection
molding, casting or extrusion is achieved with a proportion of
micro hollow balls in the float of up to 50%.
On account of the low density of the float according to the
invention, virtually all fuel-resistant plastics can be used.
Thermoplastic materials that have proven successful in
particular are POM, PA, PPS (polyphenylene sulfide), PEEK
(polyaryletherketone), HDPE (high-density polyethylene), PBT
(polybutylene terephthalate), PET (polyethylene terephthalate)
and. PPA (polyphthalamide) . In the case of thermosetting
materials, casting resins based on phenolic resins and epoxy
resins are particularly suitable.

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The production of the float from a thermoplastic material as
the plastic-resistant plastic takes place by means of injection
molding, extrusion or compression molding. If thermosetting
materials are used as the fuel-resistant plastic, the float can
be produced by casting, extrusion or compression molding.
By deliberately selecting whether to admix microspheres and/or
micro ho11ow bal1s, the density of the float can be
specifically set in a wide range from 0.15 g/cm3 to 0.5 g/cm3.
While a density of 0.4 g/cm3 is already sufficient for use of
the float in diesel fuel, floats that are used in gasoline have
a density of from 0.25 g/cm3 to 0.15 g/cm3.
In order to connect the float to the lever wire of the fuel
level sensor, the float has a receptacle for the lever wire. A
receptacle that can be produced particularly easily is achieved
with a receptacle in the float that is formed as a bore. A
bore of this type can be produced inexpensively during the
production of the float, for example by placing a core in the
float mold.
The invention is explained in more detail on the basis of an
exemplary embodiment. In the drawing:
Figure 1 shows a float according to the invention and
Figure 2 shows a detail of an enlarged representation of a
section through the float as shown in Figure 1.
Figure 1 shows a fill level sensor 1 for a feeding unit in a
fuel tank of a motor vehicle. The fill level sensor 1
comprises a thick-film resistor 2 and a lever wire 3. Fastened
in the lever wire 3 is a sliding contact 4, which slides over
the thick-film resistor 2. Arranged at the end of the lever
wire 3 is a float 5, the float 5 having a receptacle formed as
a bore 6, in which the lever wire 3 is arranged in such a way
that

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the float 3 is mounted freely rotatably on the lever wire 3.
The float has a length of 64 mm, a width of 32 mm and a height.
of 16 mm, so that the volume of the float 5 is 32.77 cm3.
Figure 2 shows a section through the float in Figure 1. 12.6%
of the float consists of POM 7, in which the microspheres 8 and
the micro hollow balls 9 are embedded. The microspheres 8 are
plastic balls 11 filled with a gas 10, as are offered by the
company AKZO NOBEL under the trade name Expancel. The
microspheres 8 have a diameter of 36 m. The proportion of the
microspheres 8 is 81.9%. The micro hollow balls 9, based on
glass, have a greater diameter than the microspheres 8. For
better representation, the microspheres 8 are drawn larger.
The proportion of the micro hollow balls 9 is 5.5%. The
density of the float 5 is 0.2 g/cm3.
The following table shows the achievable densities and the
proportions of the constituents for the float 5 in the case of
admixing 10% of Expancel 8 into the starting materials for
various mixing ratios of POM 7 to micro hollow balls 9.
POM Micro Density Proportion Proportion Proportion
hollow of float of POM of of micro
balls Expancel hollow
balls
90% 10% 0.21 13.50% 85.00% 1.50%
g/cm3
70% 3 0% 0.20 12.60% 81.9 0% 5.50%
g/cm3
50% 50% 0.19 11.50% 77.00% 11.50%
g/cm3
30% 70% 0.17 9.40% 68.70% 21.90%
g/cm3
10% 9 0% 0.13 4.9 0% 50.7 0% 44.7 0%
g/cm3
The second table shows the density and the proportions of POM 7
and Expancel 8 for various admixed amounts of Expancel 8 in the
starting materials for a float 5, comprising POM 7 and Expancel
8.

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The third table shows the density of the float 5 for various
proportions of POM 7 and micro hollow balls 9.


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Patent claims .
1. A float for a fill level sensor, comprising a fuel-
resistant plastic and an expanding means, characterized in
that the expanding means are gas-filled plastic balls (11)
as microspheres (8), and in that the fuel-resistant plastic
(7) surrounds the microspheres (8).
2. The float as claimed in claim 1, characterized in that the
proportion of microspheres (8) is between 87% and 70%.
3. The float as claimed in claims 1 and 2, characterized in
that the microspheres (8) have an average sphere diameter
of from 30 urn to 40 m.
4. The float as claimed in claim 3, characterized in that the
microspheres (8) have an average sphere diameter of from
34 m to 38 m.
5. The float as claimed in one of the preceding claims,
characterized in that the float (5) has a density of less
than 0.37 g/cm3.
6. A float with a fill level sensor, comprising a fuel-
resistant plastic and a filler, characterized in that the
filler comprises micro hollow balls (9) and in that the
fuel-resistant plastic (7) surrounds the micro hollow balls
(9) .
7. The float as claimed in claim 6, characterized in that the
micro hollow balls (9) consist of glass.
8. The float as claimed in claims 6 and 7, characterized in
that the micro hollow balls (9) have an apparent density of
from 0.09 g/cm3 to 0.1 g/cm3.

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9. The float as claimed in one of the preceding claims 6 to 8,
characterized in that the proportion of the micro hollow
balls (9) is 3% to 98%.
10. The float as claimed in claim 9, characterized in that the
proportion of the micro hollow balls (9) is over 70%.
11. The float as claimed in at least one of claims 6 to 10,
characterized in that the float (90) has a density of less
than 0.5 g/cm3.
12. A float for a fill level sensor, comprising a fuel-
resistant plastic, an expanding agent and a filler,
characterized in that the expanding agent comprises gas-
filled plastic balls (11) as microspheres (8), in that the
filler comprises micro hollow balls (9) and in that the
fuel-resistant plastic (7) surrounds the microspheres (8)
and the micro hollow balls (9).
13. The float as claimed in claim 12, characterized in that the
microspheres (8) account for a proportion of the float (5)
of from 20% to 87%.
14. The float as claimed in claims 12 and 13, characterized in
that the micro hollow balls (9) account for a proportion of
the float (5) of from 1.5% to 60%.
15. The float as claimed in claims 12 to 14, characterized in
that the float (5) contains fuel-resistant plastic (7) in a
proportion of from 5% to 14%.
16. The float as claimed in claims 12 to 15, characterized in
that the float (5) has a density of from 0.5 g/cm3 to
0.1 g/cm3.

PCT/EP2004/050810 - - 10-
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17. The float as claimed in one of the preceding claims,
characterized in that the fuel-resistant plastic (7) is
POM, PA, PPS, PEEK, PBT, HDPE, PET or PPA.
18. The float as claimed in one of the preceding claims 1 to
16, characterized in that the fuel-resistant plastic (7) is
a phenolic resin or an epoxy resin.
19. The float as claimed in one of the preceding claims,
characterized in that the float (5) has a receptacle
(6) for a lever wire (3).
20. The float as claimed in claim 19, characterized in that the
receptacle is a bore (6) in the float (5).
Dated the 7th Day of December, 2005


The invention relates to a float (5) for a fill level sensor, comprised of a fuel-resistant plastic (7), an expanding means (8) and/or filler (9), whereby the expanding means consists of gas-filled plastic balls (11) that are provided in the form of microspheres (8), and the filler consists of micro-hollow balls (9). The microspheres (8) and the micro-hollow balls (9) are surrounded by fuel-resistant plastic (7).


Documents:

02524-kolnp-2005-abstract.pdf

02524-kolnp-2005-claims.pdf

02524-kolnp-2005-description complete.pdf

02524-kolnp-2005-drawings.pdf

02524-kolnp-2005-form 1.pdf

02524-kolnp-2005-form 2.pdf

02524-kolnp-2005-form 3.pdf

02524-kolnp-2005-form 5.pdf

02524-kolnp-2005-international publication.pdf

02524-kolnp-2005-others.pdf

2524-KOLNP-2005-ASSIGNMENT.pdf

2524-KOLNP-2005-CORRESPONDENCE 1.1.pdf

2524-KOLNP-2005-CORRESPONDENCE 1.2.pdf

2524-KOLNP-2005-FOR ALTERATION OF ENTRY.pdf

2524-KOLNP-2005-FORM 27.pdf

2524-kolnp-2005-granted-abstract.pdf

2524-kolnp-2005-granted-claims.pdf

2524-kolnp-2005-granted-correspondence.pdf

2524-kolnp-2005-granted-description (complete).pdf

2524-kolnp-2005-granted-drawings.pdf

2524-kolnp-2005-granted-examination report.pdf

2524-kolnp-2005-granted-form 1.pdf

2524-kolnp-2005-granted-form 18.pdf

2524-kolnp-2005-granted-form 2.pdf

2524-kolnp-2005-granted-form 3.pdf

2524-kolnp-2005-granted-form 5.pdf

2524-kolnp-2005-granted-gpa.pdf

2524-kolnp-2005-granted-reply to examination report.pdf

2524-kolnp-2005-granted-specification.pdf

abstract-02524-kolnp-2005.jpg


Patent Number 235603
Indian Patent Application Number 2524/KOLNP/2005
PG Journal Number 28/2009
Publication Date 10-Jul-2009
Grant Date 08-Jul-2009
Date of Filing 07-Dec-2005
Name of Patentee SIEMENS AKTIENGESELLSCHAFT
Applicant Address WITTELSBACHERPLATZ 2, 80333 MUNCHEN, GERMANY
Inventors:
# Inventor's Name Inventor's Address
1 SIGRID HEIMANN TIEFER WEG 7 65817 EPPSTEIN
2 BETTINA SEIBERT PLATANENSTR. 1 65468 TREBUR
3 RAINER MOSER AM BORNGRABEN 5 65510 IDSTEIN
4 BERND PAUER WIESENSTR. 7 65817 EPPSTEIN
5 DIETER KELLER HINDEMITHSTR. 7 63743 ASCHAFFENBURG
6 DIETER KELLER HINDEMITHSTR. 7 63743 ASCHAFFENBURG
7 SIGRID HEIMANN TIEFER WEG 7 65817 EPPSTEIN
8 BETTINA SEIBERT PLATANENSTR. 1 65468 TREBUR
9 RAINER MOSER AM BORNGRABEN 5 65510 IDSTEIN
10 BERND PAUER WIESENSTR. 7 65817 EPPSTEIN
PCT International Classification Number G01F 23/76
PCT International Application Number PCT/EP2004/050810
PCT International Filing date 2004-05-14
PCT Conventions:
# PCT Application Number Date of Convention Priority Country
1 103 26 982.7 2004-06-12 Germany