Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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The present invention relates to a housing for a
valve actuating push rod in an internal combustion engine, with
a protective tube enclosing the push rod from the crankcase to
the cylinder head, rocker arm housing, or the like, one end of
said tube being adapted to be inserted into an aperture in the
crankcase and the other end into an aperture in the cylinder
head or rocker arm housing, the tube being adapted to be sealed
in the apertures by means of 0-rings, each arranged in a groove,
a machined channel or the like.
Valve mechanisms in internal combustion engines
having underhead camshafts and, in particular, overhead valves,
require, among other things, push rods. Since in the case of
air-cooled engines, for example, the push rods pass through the
cooling air space between the cylinder head or rocker arm
housing and the cran]ccase, they must be sealed off air-tight,
to prevent the cooling ribs from being contaminated with
leakage oil. This is usually accomplished by means of a push
rod housing-
Various designs of push rod housings are disclosed
in "Die Konstruction schnellaufender Verbrennungsmotoren"
(The Design of High-speed Internal-Combustion Engines), Hermann
Mettig, Walter De Gryterverlag, Berlin, New York, 1973, Fig.
162 on page 244. The third example of embodiment is a push
rod housing of this kind in which the protective tube joints
in the cylinder head and crankcase are in the form of plug-in
connections, sealed with toroidal or 0-rings. The crankcase
end of the protective tube is formed by a stop element pro-
vided with a machined groove for accommodating a standard 0-
ring and bearing, in the assembled condition, externally upon
the crankcase. This limits the ability of the protective
tube to move axially, but an additional retaining element isneeded for safe retention of the protective tube, and this
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element is screwed to the crankcase- Such design is expensive
due to many parts being required, notwithstanding difficult
assembly being involved, all of which is of considerable
importance especially in the case of mass-produced internal
combustion engines-
It is therefore a main aim of the present inventionto provide a simplified valve actuating push rod housing o~ the
type mentioned at the beginning hereof, from the point of view
of the components used to ensure reliable sealing of the said
housing, while retaining the plug-in joints between the pro-
tective tube and the cylinder head or rocker arm housing and,
at the same time, minimi~ing production costs and assembly-
According to the present invention, this purposeis accomplished in that the O-ring at one end oE the pro-
tective tube is arranged in a space formed by a groove pro-
vided in the protective tube and a groove provided in the
aperture in the crankcase or in the rocker arm housing, the
grooves uniting to form an O-ring groove of standard depth.
These characteristics, according -to the present
invention, offer substantial advantage in that they make it
possible to dispense with the need for additional components
for securing the protective tube axially, since such location
is effected within the common space accommodating the one
O-ring, whereby this space and O-ring perform a double func-
tion and are thus important. The common space is essentially
adapted to O-ring standards, i.e., depending upon the thick-
ness of the O-ring to be used, the width of the groove may
be taken from standard O-ring tables, whereas the overall
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depth of the groove, which is also given in such tables, is
divided between the two grooves forming the space accomm-
odating the O-ring. This ensures that the housing is
comp]etely sealed. Production costs are substantially
reduced and assembly of the push rod housing is considerably
simplified, since the only assembly work involved is the
fitting of the O-rings and the insertion of the protective
tube. The push rod housing according to the present
invention provides the same advantages in both air-coo]ed
and water-cooled internal combustion engines.
One o, the grooves of the common space preferably
comprises a rounded-off inlet, or lead-in, the radius of
which is between 0.5 and 1.0 of the diameter oE the O-ring
to be used. The groove of the common O-ring accommodating
space which has the rounded-off lead-in is preferably pro-
vided in the aperture in -the crankcase or in the cylinder
head or in the rocker arm housing. The groove in the
protective tube preferabl~ comprises 80% of the entire
space, and ~his provides additional advantages from a
production point of view. According to one particularly
favourable configuration of the protective tube plug-in
connection designed with the common O-ring accommodating
space, the diameter of the aperture is bet~een 1.6 and 2.05%
smaller than the maximal diameter of the groove provided in
the aperture, while the maximal diameter of the end of the
tube adapted to be inserted into this aperture is between 2
and 3% smaller than the corresponding diameter of the
aperture in the crankcase, the cylinder head, or the rocker
arm housing. This configuration, according to the inven-
tion, of the pluy-in connection for the valve-actuating
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push-rod housing has the advantage of making it possible to
take optimal account of the dual function of the accommodat-
ing space, namely sealing and axial location of the
protective tube, while at the same time facilitating
assembly.
Further advantageous configurations and develop-
ments OL the invention appear in the disclosure hereinafter.
The invention is exp]ained hereinafter in greater
detail, in conjunction with the examples of embodiment
thereof illustra-ted in the drawings a~tached hereto,
wherein:
YIGVRE 1 is a diagrammatical cross-sectional
representation of an example of embodi-
ment of a valve-actuating push rod hous-
ing in accordance with the present
invention;
FIGURE 2 is a further example of embodiment of a
valve-ac-tua-ting push rod housing in
accordance with the present invention;
and
FIGURE 3 is a cross-sectional representation, to
an enlarged scale, of detail III in
Figure 2.
In Figures 1 to 3, parts having basically similar
functions, bear the same reference numbers and in order to
simplify matters, only parts needed for an understanding of
the invention are shown in detail. In the Figures, 1 is a
crankcase, 2 is a rocker arm housing, and 3 the camshaft, of
an internal combustion engine. The valve designated 4 ls
controlled by the camshaft 3 -through a rocker arm 5 and a
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push rod 6. Push rod 6 runs from camshaft 3, through an
aperture in the crankcase, an aperture in the rocker arm
housing, and a space not shown in detail, to rocker arm S.
Between crankcase 1 and rocker arm housing 2, the said push
rod is enclosed in a protective tube. The ends of the
latter are adapted to be inserted in~o apertures 8 and 9 and
are sealed by means toroidal or O-rings. According to the
invention, O-ring 11 in crankcase aperture 8 is arranged in
a space 12 formed jointly by a groove 13 provided in protec-
tive tube 10 and a groove 14 provided in the crankcaseaperture 8. Although not specifically so illustrated in the
drawings, a groove equivalent to the groove 14 can also be
provided in either the cyli.nder head or the rocker arm hous-
ing as above-discussed. Radii R and widths B of grooves
13,].4 are in accordance with standard O-ring tables, but
dep-th T, which is also given in standard O-ring tables, is
formed by the addition of depths T13 and T14 of grooves
13,14. Protective tube 10 is therefore not only sealed but
is also secured axially by O-ring 11 arranged in crankcase
aperture 8 in the common O-ring accommodating space. in
addition to this axial location, a step 15 is provided to
restrict axial movement into the interior of the crankcase.
A similar step may be provided in the cylinder head or
rocker arm housing. O-ring 11, at the end of protective
tube 10 which is adapted to be i.nserted into aperture 9 in
the rocker arm housing, is arranged exclusively in a -trape-
zoidal or rectangular groove 16 in the protective tube.
This groove 16 comprises standard O-rinq dimensions.
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In the example of embodiment according to Figure 2,
aperture 8 in the crankcase, for insertion of protective tube lO,
is in the form of a retaining element 17 adapted to be secured
to the crankcase by means of bolts, for example. The said
retaining element again comprises a step 15 restricting the
movement of the protective tube in the one direction. Further-
more, in this example of embodiment, the ends of protective tube
lO, adapted to be inserted into apertures 8 and 9, have an
expanded cross-section, which allows the protective tube to fit
more closely to the push rod between the two ends of the tube.
Apart from thisg this example of embodiment is similar to that
illustrated in Figure 1.
Figure 3 is a greatly enlarged representation of
detail III in Figure 2, showing the common O-ring accommodating
space, and clarifying the dimensions o~ the two grooves 13 and
14. Shown here is an O-ring in its assembled, i.e. deformed,
condition, with its original diameter DR shown in broken line-
If the diameter DR o the O-ring is known, width B, radii R
and overall groove-depth T of common space 12 may be obtained
from standard O-ring tables- The overall groove depth T is
the sum of depth T13 of groove 13 in protective tube lO and
depth T14 in groove 14 running from aperture 8. Since overall
groove depth T is designed to provide optimal sealing, ~hereas
the joint must also be designed as an easily assembled plug-in
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connection, groove-depths T13 and T14, and thus diameter D14
of aperture 8 and outside diameter D13 of protective tube 10,
adapted to be inserted into aperture 8, are optimized, according
to the invention~ Diameter D14 of aperture 8 is 1.6 to 2.0%
smaller than diameter DT14 of groove 14, and maximal outside
diameter D13 of the end of protective tube 10 to be inserted
into aperture 8 is 2 to 3% smaller than diameter D14 of aperture
8. At the same time, this provides proportional groove depths
T13 and T14 The radius of the rounded off inlet or lead-in to
groove 14 is designed with a radius R14 of 0.5 to 1.0 of the
diameter DR of O~ring 11.
