Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
The present invention relates to an apparatus for indicating
the liquid level in a receptacle, more particularly the oil level
in the crank'case Or an internal combustion engine, said apparatus
comprising a measure tube extending downwards into the crankcase
below the lower~ost design oil level and an indicating member
connected to the measure tube by means of a slender ~lexible tube,
said member being operable manually to open and close by means
o~ pump and valve members connections between the ambient air,
an air chamber in the indicating member, a liquid chamber in the
indicatin~, member and the measure tube in such seauence that the
liquid q~antity trapped in the liquid chamber is raised in an
indicating tube with a transparent wall to a height corresponding
to the oil level in the crankcase.
The invention has for its chier object to provide a simple
and easily controlled improved apparatus for the said purpose
having a minimum number of moving parts and being ca~able Or
giving correct indications o~ the oil level in the crankcase,
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This object is attained according to the invention therbby
that the air chamber of the indicating member which communi-
cates through the flexible tube with the measure tube, is
provided with a pump member in the shape of a wall which is
formed at least partly of a resilient diaphragm isolating
the air chamber from the ambient air on being pushed inwards,
that further the air chamber communicates with the liquid
chamber of the indicating member through a narrow passage
which is closed as the diaphragm wall is beginning to be
pushed inwards, and that a normally closed valve member is
operable on pushing the diaphragm fully home to open commun-
ication between the measure tube and the liquid chamber to
enable indicating liquid to rise in the indicating tube to
a height corresponding to the oil level in the crankcase
by the air pressure transmitted to the liquid chamber.
The apparatus according to the invention can be construc-
ted very compact and robust by virtue of its uncomplicated
design having a minimum of moving parts. This is of the
greatest value when handling, despatching and mounting the
device. According to a further feature the apparatus can
be made leak-proof with simple means, i._. with the indicat-
ing liquid contained therein always safely trapped in any
position of the apparatus.
An ~mbodiment of the apparatus according to the inven-
tion will be described hereinafter, reference being had to
the drawings. Figs. la, 2a, and 3a illustrate in vertical
section views the measure tube of the apparatus in its oper-
ative position in the crankcase of an engine, different steps
of the operation of the device being illustrated. Figs. lb
2b, and 3b illustrate, also in vertical section views, the
indicating member of the apparatus during the corresponding
operation steps.
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Fig. la is a fragmentary section of the crankcase of an
automobile engine. The crankcase wall 1 encloses an oil
sump 2, wherein the level of the oil 3 is permitted to vary
between a highest level 4 and a lowest level 5. In the
upper part 6 of the crankcase wall there is a passage hole
7, and a slender measure tube 8 is ~ -
inserted therei~ to such a depth ~ f.~
that its open bottom end 9 reaches below the lowermost
permissible oil level 5. The measure tube 8 has its bottom
portion 10 enlarged to such a diameter, for example 5 mm,
that will still pass through the hole 7. The enlarged tube
portion 10 is of such a length that the permissible upper
oil level 4 does not reach the tube restriction 13 forming
a transition between the enlarged tube portion 10 and the
slender tube 8. The latter preferably extends somewhat
into the enlarged tube portion 10. The measure tube 8 is
held stationary in its position relative to the oil levels
4 and 5 by means of an adjustable abutment collar 15. By
means of this collar the measure tube can be adapted to
different engines of different sizes and manufacture.
The measure tube 8 is provided with a lifting member 16 for
mounting it in the crankcase and removing it therefrom,
respectively.
The measure tube 8 is connected by means of a slender
flexible tube 17 to an indicating member, Fig. lb, that is
mounted facing the driver's seat. The tube 17 should be of
the least possible dimension (1 to 2 mm internal diameter).
The housing 18 OI the indicating member is shaped at the
base with a bottom 19 and walls~ 20 defining a chamber 21
the front wall of which is formed by a diaphragm 22. 1he
chamber 21 communicates through a passage 23 with the flex-
ible tube 17 the opposite end
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of which is connected to the measure tube 8 in the engine
crankcase. The wall 20 of the chamber which is preferably
of frusto-conical shape defines together with the diaphragm
22 in its non-actuated state a very narrow (of the order
of a tenth of a millimeter) annular passage 24 forming a
connection between the chamber 21 and a circumferential annu-
lar groove 25. The annular groove 25 communicates through
a passage 26 with a conduit 27 opening at its lower end into
a valve chamber 28 and at its upper end through a neckshaped
projection 29 into a liquid chamber 30. The valve chamber
28 accomodates a valve member 31 shutting off the valve
chamber from the air chamber 21 by the action of a spring 32.
The diaphragm 22 is passed through centrally by a hole 33
connecting the air chamber 21 with the ambient air. The
central portion 35 of diaphragm 22 is reinforced by a rigid
washer or plate 34 to prevent deformation of that portion,
whereas the peripheral diaphragm portion 36 of thin rubber
is resiliently deformable and permits pushing the diaphragm
towards the chamber bottom l9.
Bèt~een the passage 23 and the valve chamber 28 there is
provided an open shallow channel 37 which forms an air pass-
age between the valve chamber 28 and the passage 23 even
when the diaphragm is pushed fully home against the chamber
bottom l9.
A check valve 38 at the chamber bottom l9 preventsta~r
from flowing away from chamber 21 when it i~ pressurized
whereas it will open immediately to admit air at vacuum in
the chamber. The valve member 31 is shaped with a projection
39 extending some tenths of a millimeter beyond the chamber
bottom l9. Thereby the valve member 31 will open when the
diaphragm 22 is pushed so as to abut the chamber bottom l9.
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The liquid chamber 30 of the indicator housing communi-
cates through a hole 40 at its base with the indicating tube
41 the outer wall of which is a sight glass 42. The indicat-
ing tube 41 opens at the top into a safety chamber 43 commun-
icating with the ambient air through a hole 44.
The indicator liquid 45 held in the chamber 30 is of
such volume that liquid can rise on pressure increase in
chamber 30 the whole length of the tube 41 without the air
held in chamber 30 reaching the communication hole 40.
The both passages 27 and 44 open into their respective
chambers 30 and ~3 within necks 29 and 46, respectively, ex-
tending into the chambers. The height of these necks is
such that the passages terminate at the centre of the respec-
tive chambers, to prevent liquid leakage during shipmen,tt and
handling when the position of the indiaator housing will be
indeterminate,
The functioning of the apparatus will now be described,
Figs. la and lb illustrate how the indicator apparatus
mounted at an automobile engine functions during operation
of the vehicle. The oil 50 held in the crankcase, Fig. la
has a normal operation level 51 which oscillates somewhat
upwards and downwards. The movements of the vehicle and
engine cause the oil upper surface to become rather agitated.
The oil level 52 of the oil within the measure tube lO will
pulsate accordingly and will press and aspire air held in the
measure tube 8. There will never bé any build-up of pressure,
however, since the measure tube and the flexible tube com-
municate directly with the ambient air through passage 23,
chamber 21 and the central diaphragm hole 33. This is shown
in Fig. lb with arrow 53. A pressure increase caused by
temperature rise is prevented by the same means. The arrows
55 in Fig. lb show how the pressure chamber 30 of the indica-
ting member communicates with the ambient air in a
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Similar manner through passages 27 and 26 and the annular
passage 24, chamber 21 and the hole 33. When the engine
is running -the whole indicating system is uncharged and does
not give any indication in the shape of a liquid column in
the tube 41.
When the oil level shall be checked,for example when
filling petrol, the engine is stopped. The driverapplies
a finger 60 against the indicator diaphragm 22 as shown in
Fig. 2b. The finger by pushing the diaphragm will close
the diaphragm hole 33 in the first place. This will suspend
communication with the ambient air of the tube assembly 18,
8 and 10, on one side, and of the passage system with the
indicator liquid chamber 30, on the other. When the dia-
phragm is pushed inwards according to arrow 61 the annular
pàssage 24 is closed immediately. This results in isolating
the liquid indicator completely from the air chamber 21 as
well as from the tube assembly connected to the oil sump.
The diaphragm is pushed further by the finger to engage the
bottom 19 of the air chamber 21. Thereby the air held by the
chamber 21 must escape. This air will flow through passage
23 to the flexible tube 17 and further downwards through
measure tube 8. Oil which may stand within tubes 8 and 10
will be evacuated in that operation. The oil surface 52 is
forced downwards to the bottom edge 9 of tube 10, and the
air will rise as bubbles 62 through the crankcase oil. By
reason of the narrowness of the tubes the air volume 21 will
be sufficient, in spite of its relatively small magnitude,
for an efficient scavenging of the whole tube assembly. In
order not to be subjected to pressure shocks causing faulty
readings the liquid indicator 30 with its internal system of
passages is completely shut off during the whole scavenging
sequence by the closing of the annular passage 24.
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Since the diaphragm 22 has a resilient portion adJacent
its periphery only the outer diaphragm portion is deformed
while the flat central portion is pushed against the chamber
bottom 19. Any influence of different finger sizes or the
like is eliminated thereby. The valve member 31 (Fig. 3b)
is pushed against its projection 39 by the diaphragm immed-
iately before the latter reaches the chamber bottom 19. The
valve member 31 then will open, and communication is estab-
lished between the liquid indicator chamber 30, the passage
27, the valve passage, channel 37 and the assembly 23, 18,
8 and lO (Figs. 3b and 3a). Oil outside tube lO then will
be forced up through the tube. Air within this assembly
will be compressed somewhat and will thus transfer the oil
pressure within the crankcase to liquid chamber 30. The
indicator liquid 45 sinks and simultaneously the liquid in
the indicator tube 41 will rise. The resulting liquid column
is directly proportional to the oil level in the crankcase.
A suitable graduation at the indicator permits a direct
and swift reading of the oil level in the crankcase, without
taking any special steps.
When reading has been effected the finger pressure on
the diaphragm is released a~d the latter resumes at once its
flat initial shape. Thereby the valve member 31 will close
in the first place. The indicator is now again completely
shut off, but the liquid level can still be read. Ambient
air enters on return of the diaphragm through the diaphragm
hole 33 to prevent a vacuum to form in tube system lO, 8,17
and 23. It is not desirable that oil is aspired into the
system, and by that reason the check valve 38 is provided in
the chamber bottom 19. This valve prevents
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pressure to escape from chamber 21 the wrong way during
pressure build-up but permits, if necessary, air to enter
during the return to initial~` position of the diaphragm 22.
Shortly before this position is reached the passage 24 is
opened. Thereby the liquid indicator is zeroized, and
complete apparatus resumes the neutral state illustrated
in Figs. la and lb. Now as before the measuring member~
is insensible to temperature and pressure variations.
