Claim
3.
A four-stroke internal combustion engine according
to claim 1 or 2, in which the variably timed transmission includes
three superposed concentric members, i.e. an inner member constituted
by a drive shaft [17], an outer member constituted by a sleeve [28]
supporting a gear [20] for coupling the two crankshafts [4] [5],
and an intermediate member located between said inner and outer
members and constituted by a tube [32] which slides with respect
to said inner and outer members, the sleeve [28] being held in a
bearing plate [15] by means of a double-row angular contact bearing
[16], in which the shaft [18] of the second crankshaft [5] has one
end which abutes one end of the drive shaft [17], said ends having
straight male splines and corresponding female splines, so as to
enable their coupling and self-centering of the three members with
respect to the shaft [18] of the second crankshaft [5] when the
bearing plate [15] is engaged in an opening of the engine unit,
and enable the transmission to be removed without having to remove
the second crankshaft [5], in which a bearing [22] has a mounting
ring [25] which forms the housing of the outer ring [26] of a bearing
[23], the inner ring [27] of which is mounted on the sleeve [28]
so as to hold the drive shaft [17], in which a spacer [29] extends
between the inner ring [27] of the bearing [23] and the inner ring
of the angular contact bearing [16], said spacer serving to take
up the space between said rings and holding axially the ring of
the angular contact bearing [16] against a shoulder of the sleeve
[28], in which a single nut [30] holds the inner rings of the bearing
[23] and of the angular contact bearing [16] and the spacer [29]
on the sleeve [28], in which the drive shaft [17] has, on the side
of the mounting ring [25] , helical or straight splines [31] onto
which the sliding tube [32] is engaged, the inner surface of which
has helical or straight splines [33] so as to enable said tube [32]
to travel helically or linearly along the drive shaft [17], in which
the inner surface of the sleeve [28] has helical splines [35], the
helix of which is contrary to that of the splines of the drive shaft
when the latter are helical, in which the sliding tube [32] has
one end permanently free outside the sleeve [28], said end being
held by an inner ring of a double-row angular contact bearing [36],
the outer ring of said bearing [36] being rigidly connected to a
holding member [37] of the thrustor, and in which the helical splines
are arranged so that when the sliding tube [32] travels out of the
sleeve, said tube reduces the lead angle between the crank of the
second crankshaft [5] and the crank of the first crankshaft [4].
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