Note: Descriptions are shown in the official language in which they were submitted.
75~8
INTRODUCTION ANI~ BA~K~.~OUND OF Tl~ I~VENTIO~
The present invention relates -to improvements in rocking-piston
machines~ i.e. rrlotors, compressors and pumps and particularly to combustion
engines. This app]ication is a division of Application Serial No. 272,845,
filed February 28, 1977.
The drawbacks of the existing trunk piston machines are the well-
known, comparatively rough and noisy running due to their heavy pistons with
piston slap, high oil drag due to their piston skirt and in general their
complicated, heavy and expensive construction.
These drawbacks can be overcome in rocking-piston machines, for
example as disclosed in Canadian Patent No. 927697 or the corresponding
United States Patent No. 3,695,150 and United Kingdom Patents Nos. 1316775
and 1388904. However, the guiding of rocking pistons in their waisted
cylinders is not without problems.
Accordingly one object of the present invention is to improve the
guiding of rocking pistons and to improve the machines in other respects.
BRIEF SUMMARY OF THE_ NVENTION
The invention provides a rocking-piston machine, for example an
engine or compressor or pump, with at least one cylinder, wherein a skirtless
rocking piston reciprocates, this rocking piston being provided with periph-
eral sealing means pressed hydraulically against the waisted cylinder wall,
the piston also being connected rigidly to a connecting rod which is artic-
ulated to a crankshaft or eccentric shaft. The cylinder may have a circular,
oval, square, rectangular or any other suitable cross-section and is waisted
according to the rocking movement of the periphery of the rocking piston.
Such rocking-piston machines have a piston without skirt and
gudgeon pin, forming one piece with the connecting rod running in a short,
waisted cylinder. The rocking movement causes the gas pressure to act
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alwa~s dircctly ;llong the ax;s of the conllecting rod, so that there is no
latcral compollcllt of this load to callse piston slap and thercfore noise and
wear.
Because the piston, as it moves between top and bottom dead
centres, rocks back and forth in the cylinder, highly advantageous, asymmet-
ric port timing can be readily adopted for two-stroke petrol or diesel
engines, and the compressed gas is transferred from side to side of the
combustion chamber, thus encouraging soft and complete combustion and low
exhaust pollution in either two- or four-stroke engines. With a short rock-
ing piston of very light weight, the primary and secondary vibration forcesare less than half as severe as those of a conventional engine, so fewer
cylinders can be used without exceeding acceptable levels of vibration. The
skirtless rocking piston causes low friction losses, because the oil drag is
very low. This means higher mechanical efficiency and much easier cold
starting than with the conventional piston. Experimental rocking-piston
engines on test beds and in vehicles have confirmed these facts, but showed
that in particular the longevity of the piston-guiding device was inadequate.
The object of this invention is to create a rocking-piston machine of the
kind described above but which runs perfectly as an engine, compressor or
pump over a long period of time.
According to the invention there is provided a rocking-piston
machine, as an engine or a compressor or a pump, of the kind comprising a
skirtless piston, a waisted cylinder in which said piston reciprocates, a
connecting rod rigidly secured to the piston, and a crankshaft to which the
connecting rod is articulated, characterised by the provision of guiding
means on the piston to slidingly engage with variable guiding pressure
against the internal boundary surface of the cylinder, said guiding means
being responsive to variable fluid pressure for varying said variable
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guicling l~ress11re, i111d pu~ ir1g mea11s for creating sc1ic1 var:iable fluid
pressure, the pl1mpi11g me.ll1s 1-eing s~1c11 th.lt the speed of operation thereof
a11cd the variable fluic11~rc?ssure anc1 the var;able guidi.ng pressure increase
and decrease in depen(1ence upon the speed of the machine.
Brief Description of the Drawing
The following explanation describes a few simplified examples of
execution, which have by no means optimal dimensions and whose individual
features are interchangeable. In all these examples of execution the piston
surface as well as the piston stroke is the same. Further details necessary
for optimum running of the rocking-piston machine are briefly described and
illustrated in the drawing:
The drawing shows in:
Figure l a cross-section of the middle part of an engine or
compressor according to the invention,
Figure 2 a horizontal section of its circular rocking piston,
Figures 3 to 7 enlarged cross-sections of various piston edges,
Figure 8 a cross-section of an engine or compressor with a
rectangular cylinder,
Figure 9 a horizontal section of this cylinder and rocking piston,
Figures lO and ll a rocking-piston slide-valve engine in cross and
longitudinal section,
Figure 12 a plan view of the rectangular cylinder with horizontal
section of the rocking-piston,
Figures 13 and 14 a variation of this rocking-piston in half
longitudinal and in half cross-section,
Figure 15 an enlargement of the piston-guiding device of Figure 13,
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5'6~
F`;~ures1~ to l9 enlar~red var ations o~ the piston edge in longi-
-tuAinal section,
Figure~20 and 21 an application Or an engine approximately accord-
ing to Figure 10 to 12 in a vehicle in elevation and plan view.
Detailed Description of the Preferred Embodiments
Figure 1 shows a conventional engine or compressor equipped with
a waisted cylinder and rockingj-piston 1 according to the invention. This is
the first generation of the rocking-piston machine, where the lower part of
the original cylinder is eliminated and thereby shortened cylinder 2 is
~ e rAp~A/~ ~R~ S~6~o~ Q~ 6 ~j~
1 ~ machined not cylindrically, as usual, but in a waisted shape\according to the
rocking movement of the piston edge 3. This machining is more complicated,
but less costly, because the length of the original cylinder is reduced by
one-third or even a half and much greater tolerances are admissable. For
this machining, a kinematic inversion can be used, whereby the boring tool
is rotated in a fixed plane, and the cylinder block is fed up and down
relative to it and, at the same time, rocked by means of a crank-and-cam
mechanism. However, it is simpler to fix the cylinder block and machine it
by means of a special boring spindle whose tool is fed radially, cyclically
and automatically. This can be achieved by a three-dimensional cam or by
numerical control. By this means the simultaneous machining of the top and
bottom parts of the cylinder, i.e. cone 4, is possible. This cone 4 serves
to fit and remove the rocking_piston 1 from below, which is normally pos-
sible, sometimes even without having to dismantle the crankshaft. The con-
version is even simpler in the case of exchangeable cylinder liners, for
instance dry liners 5, wet liners or air-cooled individual cylinders, whose
waisted surfaces can be machined for instance on a special lathe. Further-
more~ tubes can be cold formed, i.e. waisted by lateral pressing and then
cast in~ which makes for low costs. As is known from conventional cylinders
~_ - 4 _
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and Wankel trochoids, t~le walls of the waisted cylinders can, if necessary,
be coated wear-resi~tantly and ground, or honed by flexible tools like
"Flexhone" reg. The geometrical shape of the waisted cylinders can be cal-
culated very accurately, as explained in Figure 8.
The rocking_piston 1 of an Otto engine according to Figure 1 is
welded to the connecting rod 6. The light construction reduces the primary
inertia forces to about half those of a conventional trunk piston; the sec-
ondary inertia forces are even mor~ reduced by the long connecting rod 6 with
its upper rotating point 7 slightly under the piston crown 8. This is a very
important feature for four-cylinder four-stroke in-line engines. These low
inertia forces make it possible to use a light connecting rod cover ~ as well
as a light counter-weight 10. The rotating point 7 travels not on the longi-
tudinal axis of the cylinder, but preferably on an elongated loop 11. With
the usual parallel valves, the rocking movement of the piston crown 8 after
the top dead centre causes a violent intake swirl, provided that with clock-
wise rotation of the crankshaft the inlet comes from the right. Super-
imposed on this inlet swirl is a uniflow transfer 12 of the charge, which is
generated by the rocking movement of the piston crown 8 on the region of the
firing top dead centre. This causes a very intense mixing of the charge.
The sealing ring 13, which mainly takes up the combustion pressure, has a
cambered edge, is fitted under radial prestress and has a considerable radial
slide. The gas force acts in the centre of the sealing ring 13 and at right
angles to its sealing plane, i.e. always in the direction of the crank pin
1~. Thereby, no notable lateral component of the gas force and therefore no
piston slap is created. It is just this fact which makes it possible to
dispense with the piston skirt and therefore to render the rocking-piston
possible.
However, due to the inertia of the rocking-piston 1 and of the
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connecting rod 6, dynamic lateral forces are generated by the rocking move-
ment and the figure-of-eight loop 11. These dynamic forces increase to the
square of the increasing rotational speed and are zero at the stroke dead
centres. The guiding ring 15, acting as a second sealing ring, has an edge
cambered either uniformly or according to the rocking movement and is pre-
stressed against the base 29 of its groove, in order to guide the rocking-
piston 1 in the bore of the cylinder 2 without any play. This prestress
has to be sufficient to take up the dynamic lateral forces mentioned above
as well as the superimposed reactions of the friction forces due to the
radial slide of the sealing ring 13 and the rotation of the crank pin.
According to the invention, the prestress is achieved by hydraulic means,
for example by heat-resistant, oil-filled pressure tubes 16, 16', for example
of P.T.F.E. material, arranged at the base 29 of the groove. According to
Figure 2, each of the pressure tubes 16, 16' is on a different side of the
cylinder plane 2 A and is for example bonded in the bore 17 located near the
cylinder plane, while their free ends are closed in such a way that the
opposite pressure tube 16' is locally supported and that the pressure tube
16, 16' seals the whole circumference of the guiding ring 15. Each bore 17
leads to a longitudinal duct 19 formed by the profile 20 of the connecting
rod 6 and via a non-return valve 22 in the connecting rod big end to a pref-
erably non-loaded zone of the big end bearing.
This system works as follows: after starting the engine, both oil
columns in the ducts 19 are put under pressure in the region of the top dead
centre by inertia. This pressure is transmitted to the pressure tubes 16,
16' and prestresses the rocking_piston via the guiding ring 15 against the
wall of the cylinder 2. The height of the guiding ring 15, i.e. its interior
surface, has to be such that the prestressing force is more or less the same
as the dynamic lateral forces mentioned above. The oil pressure and with it
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the prestressing force rises to the square of the increase of the rotating
speed and therefore in the ss;me proportion as the dynam;c lateral forces. As
a result, the machine can run at any speed furthermore, it always works with
a minimum of friction and wear, because the prestressing force behind the
guiding ring 15 is never stronger than is necessary for a safe guiding of the
rocking-piston. Furthermore, this prestressing force is independent of the
wear of the guiding ring 15 and of the wall of the cylinder 2, because this
wear is automatically adjusted by the creeping of the material of the oil
tubes 16, 16', i.e. its permanent deformation. The non-return valve 22 hin-
ders the oil from flowing down the ducts 19 under the influence of its inertiain the region of the bottom dead centre, where this force is relatively
small. The sealing element 23 of the non-return valve is preferably conical
and has about the same specific weight as the oil, i.e. may be of plastic
material. This hydraulic piston prestressing device also functions automat-
ically when the machine speed is reduced, whereby a certain untightness of
the sealing element 23 with a soft spring and short stroke is favourable.
An oil scraper ring 24 with sharp edge is arranged in the
third ring groove radially slideable and is radially prestressed. Its
action may be improved by U-shaped oil-catching channels 25 with profile 26
on both sides of the connecting rod 6. The rocking-piston 1 needs very
little lubrication oil, and its surface in contact with the wall of
the cylinder 2 is only a few percent of the surface of a comparable,
conventional trunk piston. This improves the mechanical efficiency and
considerably reduces the oil drag under cold starting conditions,
thereby, enabling the use of a smaller starter and a smaller battery.
Furthermore, this low friction makes for a very low, stable idling
speed. Oil cooling of the rocking-piston 1 can easily be achieved by an oil
flow through the centre 27 of the connecting rod 6, with oil return if nec-
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1~7~
essary.
The hydralllic piston-guiding device described above can be sim-
plified by connecting the right pressure tube 16 to the end 18' of the left
pressure tube 16' instead of to the bore 17. The resulting single tube 16/16'
must be contracted at the point 18' so that the oil cannot flow freely to and
fro between the right and left halves 16 and 16' of the pressure tube; other-
wise, the piston guiding would be affected by interconnected prestressing.
In other words, each half relative to the cylinder middle plane 2 A of the
piston guiding system must have its own prestressing.
There are further possibilities to simplify the hydraulic piston-
guiding device. For instance, the right pressure tube 16, which has mainly
to support the reactions of the friction forces mentioned above, can be
filled with oil and closed at both ends. However, the automatic ad~ustment
of the wear of the guiding ring 15 and the wall of the cylinder 2 takes place
on the left hand side only, i.e. asymmetrically. A further simplification
would be to omit both non-return valves 22, provided it is possible to use
the hydrodynamic pressure differences in the connecting rod big-end bearing
to establish the necessary oil flow and pressure conditions in the pressure
tube 16, 16'. This could be the case with a rocking-piston 1 running at a
constant speed, for e~ample in a compressor.
According to Figure 3, the pressure tube 16 is replaced by an
elastic supporting and sealing ring 30 functioning like the pressure tubes
16, 16'. This variant simplifies the oil supply to the ring 30, which guides
the rocking_piston during starting. Xowever, synthetic elastic materials
have proved to be insufficiently heat-resistant for combustion engines.
As a variant, the pressure tubes 16, 16' can be stiffened, for
instance by undulated steel springs or the like preferably arranged inside
the tubes. These springs produce the necessary prestressing of the rccking_
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piston for starting the machine, i.e. in the absence of oil pressure in the
pressure tubes 16, 16'.
In Figure 4, the guiding ring 15 with covered ~oint is replaced by
two guiding rings 15 a with cambered edges arranged in one groove. The base
of the groove is semi-circular and preferably grour.d, so that t'ne pressure
tube 16 can oscillate in it when the guiding rings 15 a slide radially
against each other due to the rocking movement of the piston 1. Similarly,
~hree or more thin guiding rings can be provided.
In Figure 5, the sealing ring 13 is arranged directly on top of
the guiding ring 15. This causes a reduced radial slide of the sealing ring
13 and has proved to work very well. However, with this arrangement of the
rings 13 and 15 in one groove, aLmost the full gas pressure acts on the pres-
sure tube 16, which is additionally heavily loaded by high temperatures, in
spite of an insulation strip 31.
According to Figure 6, this disadvantage is avoided by arranging
a preferably very thin, flexible partition plate 32 between the sealing ring
13 and the guiding ring 15. This flexible partition plate 32 can extend over
the whole piston surface and is covered by a separate piston crown 33, in the
edge of which the sealing ring 13 is located. A separate feature of the
guiding rings 15 b is -that they have a common camber or dome 34 which, how-
ever, scrapes the oil on the wall of the cylinder 2 very strongly upwards.
Therefore, at least a double oil scraper ring 24 is necessary.
More and different possibilities are presented by rocking-piston
engines of the second generation, which are not adaptations, but new designs.
These machines have circular, oval, square or rectangular cylinders and pref-
erably a lubrication system which renders the oil scraper ring 24 super-
fluous. Circular cylinders can normally be machined and the rocking_pistons
fitted from below, whereby the cylinder and the cylinder head can be made in
~,.
75&8
one piece, possib]y together with half of the or the whole crankcase. This
kind of` machine is, of course, very simple and light, the more so as the
smooth running of the rocking_piston without piston slap and with a minimum
of vibration allows for a very light, thin-wall construction.
Figure 7 shows, as an example of execution, a circular rocking-
piston assembled from a piston crown 33, the partition plate 32 and a base
plate 35 with a downward stepped rim in which the quiding ring 15 and the
pressure tube 16 are located. The components 33, 32 and 35 can be assembled
for instance by spot-welding and bonded to a hollow connecting rod 36 shaped
to give an optimal strength-to-weight ratio and consisting for example of
glass-fibre or carbon-fibre stratified plastics or of magnesium. The circu-
lar cavity 37 may be used for oil-cooling and be connected to the pressure
tube 16, the oil being taken from and returned to an encapsulated forced-
feed lubrication as is shown in Figures 10 and 11. Such rocking-pistons and
connecting rod assemblies are extremely ]ight and therefore need a corre-
spondingly low prestressing.
Figures8 and 9 illustrate a rocking-piston machine as an engine
or compressor with a rectangular cylinder 40 with side proportions of two to
one and the long sides parallel to the crankshaft. This shape of cylinder is
especially suitable for air-cooled machines with air-stream flowing parallel
to the crankshaft, that is for example for compressors, stationary engines
or moped and motorcycle engines installed longitudinally and having one
cylinder or two cylinders in Vee or opposite configuration and preferably
with cardan shaft drive to the rear wheel. Furthermore, this rectangular
shape of the cylinder 40 allows very large, parallel valves 41 and 42, a
central sparking plug 43 and a very short connecting rod 44, which can be
forked if necessary. This shape of cylinder 40 is also particularly suitable
for side valves or for a laterally arranged, long rotary valve with favour-
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ably small dia~neter. The cylinder 40, the crankcase 45 and if possible thecylinder head are cas-t in onepiece of light metal with cooling ribs, its
open and being closed by a cover 46. This layout enables the waisted cylin-
der walls 47 and the flat rear wall 48 to be machined from the open end by
tools guided by cams or m~merical control.
The waisted cylinder walls 47 are parallel to the theoretical
cylinder curve 52 at a distance 51 which is the radius of the camber or
dome of the guiding strip 49. The theoretical cylinder curve 52 is drawn by
the upper ends of a "T" with a width 53 corresponding to the theoretical
piston width and a height 54 corresponding to the length of the connecting
rod 44 when the lower end of the "T" moves a circle 55 with a radius 56 cor-
responding to half of the piston stroke. The theoretical cylinder curve 52
was first empirically and then mathematically researched. This led to the
discovery that for a rocking-piston crank drive symmetrical to the cylinder
axis, mathematically accurate cylinder curves 52 do in fact exist irrespec-
tive of all the ratios of piston width 53, connecting rod length 54 and half
piston stroke 56. However, for extreme ratios, these curves 52 oscillate too
much, whereas for the usual geometric ratios of piston machines they are
normally favourably shaped for waisted cylinders. A particularity of these
theoretical cylinder curves 52 is that, for instance, an enlargement of the
theoretical piston width 53 causes the curves to oscillate, whereas a further
enlargement of the piston width causes these oscillations to disappear. An
advantage of rectangular or square rocking-pistons is thæt they give mathe-
matically accurate waisted cylinder walls 47, provided the crank drive is
symmetrical to the cylinder axis. Circular rocking-pistons have no constant
theoretical piston width 53 and therefore a compromise has to be found to
minimalise the local radial inward and outward movements of the guiding ring
15, these ring movements being easily taken up by the pressure tubes 16. In
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1~7S~B
order to firld the best possible compromise, a programme has been worked out
which comprises about a thousalld punched cards of a big computer.
The waisted cylinder walls 47 and also the wall of a circular,
waisted cylinder may differ slightly from the mathematica] shape to further
improve the rocking piston running. For instance, the cylinder width can be
slightly narrowed at the places where the dynamic lateral forces, due to the
inertia of the rocking_piston 51 and connecting rod 44, are high, in order
to locally increase the prestressing of the rocking-piston against the
cylinder walls 47. Such a reduction of cylinder width can also be provided
in the hotter region of the cylinder in order to compensate for thermal expan-
sion.
The rocking-piston 57, shown in bottom centre position, has sup-
porting ribs 58 and forms one piece with the connecting rod 44, for example
in light metal; the rectangular piston crown 59 with the partition plate 60
is screwed or bonded to it. The piston ring 15 has to be superseded by a
piston rectangle which is composed of two guiding strips 49 with the dome
radius 51 and two sealing strips 50 with flat or domed edges. The strips 49
and 50 can be made in one piece to form identical corners, two of which make
up the piston rectangle, ~these corners 49/50 act as a second piston seal due
20 to their overlapping ends and to the pressure tubes 61 and 62. On a clockwise
rotating rocking_piston 57, preferably the right pressure tube 61 is filled
with a liquid and closed at the ends, whereas the left pressure tube 62 has a
connection 63 bonded to a bore in the rocking-piston. This connection 63
leads to a longitudinal bore 64 in the connecting rod 44 which bore is closed
at both ends. The non-return valve 22 is pressed into the longitudianal bore
64, below which a gas-filled, elastic bubble 6-5 is located. The pressure
tube 62 and the longitudinal bore 64 are filled with liquid which is under
sufficient pressure from the compressed elastic bubble 65 to start the
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machine. ~hen the machine is runni~K, this pressure increases automatically
under the influence of the inertia of the liquid column in the longitudinal
bore 64 in the region of the top dead centre, thereby giving the hydraulic
piston-guiding explained in Figure 1. ~lowever, in the ex&mple of execution
according to Figures 8and 9, the hydraulic system is hermetically sealed and
works without an oil feed from the crankshaft, whereby no forced-feed lubri-
cation is necessary and no air can penetrate. In addition, there is a free
choice of the hydraulic liquid with regard to its specific weight~ boiling
and freezing point, viscosity etc.
To relieve the gas pressure on the guiding and sealing strips 49,
50 separate sealing strips 66 are provided above them ana are laterally
slideable in the s&me way as the sealing ring 13. These separate sealing
strips 66 are preferably constructed more or less in the same way as their
counterparts 49, 50 and may be stamped out of sheet metal. These sealing
corners have to be forced apart by suitable springs which replace the natural
prestressing of the sealing ring 13, these springs being arranged for example
in transverse grooves of the piston crown 59.
The layout of the crankcase 45 is similar to that of small two-
stroke engines with for inst&nce a light-spring automatic inlet valve through
which additional air is sucked in. This additional air is compressed inside
the crankcase 45 and pushed into the cylinder through several transfer chan-
nels 67 arranged at the bottom of the right cylinder wall 47. This occurs in
the region of the bottom dead centre &nd according to the diagr&m 68, 69,
asymmetrically to the dead centre. With compressors anti-clock~se rotation
may be preferable so that less piston stroke is lost. Such compressors may
have guiding and sealing strips 49, 50 made from plastic material, for in-
stance on a P.T.F.E. base and possibly have no sealing strips 66, making them
suitable for dry, unlubricated runnlng. The additional air mentioned above
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serves to cool tl~e connecting rod 44 and the rocking piston 57 and to in-
crease the output o~ compressors and engines. With four-stroke Otto engines,
the additional air is conducted to the exhaust gases at the end of the work-
ing stroke which encourages the scavenging of the combustion chamber and later
on an afterburning of the subsequent eYhaust gases. Furthermore, at the end
of the intake stroke, during which an especially rich fuel-air mixture is
drawn in from the top of the cylinder, additional air is fed in from below
and forms an air layer on top of the rocking-piston, which produces a simple
charge stratification with the rich mixture close to the sparking plug 43.
It is, of course, understood that the transfer channels 67 will be situated
and shaped in the walls of quadrangular or circular cylinders in such way as
to create the best possible conditions for increased output and/or charge
stratification.
Even more promising is a combustion engine of the third generation
as presented in Figures 10 to 12 in the bottom dead centre position. This is
a small Diesel rocking-piston slide-valve engine working with two-stroke cycle
and it uses all the inherent advantages of the rocking-piston, leading to a
very simple, light and compact construction, reduced consumption and air
pollution and particularly low running noise.
The housing of this in-line engine consists of a cylinder head 70,
a cylinder block 71 and a crankcase half 72 in light metal or cast iron and
is assembled with a minimum of parallel screws 73, 74. Here, too, the cylin-
der has a rectangular shape again with the ratio of two to one, for instance,
but unlike Figures 8 and 9, the short sides are parallel to a crankshaft 75.
The waisted running surfaces are now on the short sides of the rectangular
cylinder and consist of separate, waisted cylinder inserts 76 or 77 which are
installed in a rectangular cross-section aperture 78. This aperture is pre-
cast in the cylinder block and broached and then possibly smoothed and cali-
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brated by a conical punch. The waisted cylinder insert 76 is of rigid con-
struction and has a fixing bolt 79 friction welded to it. Simpler is a thin-
wall insert 77, the top of which is bent to form a corner 80 which is clamped
by a cylinder head 81. The waisted cylinder inserts 76 and 77 can be manu-
factured easily by conventional methods of profile production and may be
coated, as known for instance from the Wankel trochoids and ground in a simple
manner, their coated and ground surfaces being, however, three times smaller
than those of a comparable Wankel engine. The long, flat cylinder wall 82
can have a cylinder insert 83 made of flat sheet metal with a bent corner 84
and stamped gas ports 85. In this case, a tooth 86 or the like serves to seal
and fix the corners 80 and 84 against each other until they are clamped by the
cylinder head 81. In order to prevent the thin-wall cylinder inserts 77 and
83 from bending under thermal expansion, they must be bonded to the aperture
78 of the cylinder block 71 or pre-stressed outwards or be very flexible. All
the cylinder inserts 76, 77 and 83 are exchangeable, if necessary, for easy
engine overhaul. The very narrow cylinders give large cylinder interspaces
86 in which the exhaust ducts 87, inlet ducts 88 and transfer channels 89 are
arranged and which allows even air-cooling.
The force-fed lubrication of the crankshaft by a usual oil pump is
encapsulated with respect to the crankcase which requires the sealing of the
crank pin 91 and the journal 92 bearings. The sealing of the crank pin 91
bearing is effected by tapered disc springs 93 which, for assembly, are
diametrically split and run on tapered collars of the crank pin 91 and are
therefore automatically prestressed axially when fitted. As variations, a
C-shaped steel seal 95, preferably with plastic insert, is advantageous,
particularly so if combined with a bearing shell 96. These sealing elements
93 and 95 abut against and seal the big-end of the connecting rod 97. The
oil return from the crank pin
7S68
91 bearing takes place through a number of outwardly inclined bores 9O under
centrifugal force into an annular space 99, into which also the oil from the
~ournal 92 bearing, i.e. the main bearing, escapes. The annular spaces 99
are sealed against the crank discs 100 by sealing rings 101 arranged in cir-
cular grooves of the crank discs 100 and run in large-diameter bores of the
cylinder block 71 and crankcase lower half 72. The big sealing rings 101 are
for instance made from bent spring-steel strips may be for instance
P.T.F.E. coated; their diameter may be considerably reduced by feeding the
oil from the crankpin 91 bearing back through bores 102 inclined inwards.
This encapsulated, force-feed crankshaft lubrication, together
with a tight and close crankcase, if necessary equipped with fillers, makes
it possible to employ a simple two-stroke crankcase pump and thus eliminate
a separate, noisy charger. It also serves to cool the rocking-piston 105
and connecting rod 97 assembly by air. In addition, this lubrication system
largely avoids the pollution of the lubrication oil by combustion gases and
carbon deposits especially with Diesel engines, thereby replacing highly
undesirable oil change by simple and more economic topping-up. Another
advantage of this encapsulated lubrication system is that it dispenses with
oil-scraper rings which, as well known, produce great friction losses and
have a highly varying efficiency. However, this feature cannot be used with
conventional trunk pistons, the skirt of which need oil splash from the
crankshaft.
The rocking-piston 105 and connecting rod 97 are made in one
piece, for example as a light metal casting, the connecting rod cap 104 being
preferably of steel to reduce the danger of big-end seizing at very low tem-
peratures, which danger could of course be avoided by making the heavily
dimensioned crankshaft 91/92/100 out of light metal as well. The rocking-
piston 105 has two integral, asymmetric flat slides 106 which also stiffen
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the long piston sides. The connecting rod 97 has a cross-shaped 108 or
alternatively ~I-shaped profile and is in one piece with one or more horizon-
tal ribs 107 supporting the flat slides 106 and has on each side a vertical
wall 109, all of which makes for a very stiff and easy-to-cast connecting-
rod rocking-piston slide-valve assembly suitable for Diesel operation. The
flat slides 106 dip in and out of local apertures 110 of the crank discs 100,
provided the connecting rod 97 is not lengthened accordingly. The rocking-
piston 105 has a rectangular, continuous groove strengthened, if necessary,
in which guiding strips 111 and sealing strips 112 are located. Each guid-
ing strip 111 and sealing strip 112 forms one piece, i.e. a guiding and
sealing corner 111/112. Two such identical corners 111, 112 are arranged in
one common groove with their ends abutting, forming a pair. Two such pairs
are arranged on top of each other, with the abutting ends of the top pair
diagonally opposite to the abutting ends of the lower pair, making for a very
simple and effective sealing. This system of four identical sealing corners
111/112 has only four joints, all overlapping, whereas the simplest gas seal-
ing of a rotary engine has fifteen partly different dealing elements with
twelve open and six overlapping joints. Furthermore, the sealing length of
a rocking-piston is 2.6 times less than that of a comparable rotary piston,
and the dwell time of the gases is shorter. The guiding and sealing corners
111/112 should be made from convenient, wear resistant material or must be
wear resistantly coated, especially the dome 113 of the guiding strips 111.
Such material and coating are well-known from trunk piston and rotary piston
research.
The sealing strips 112 are prestressed against the flat cylinder
walls 82, 83 for instance by ]ight undulated springs 114, whereas preferably
the right guiding strips 111 are prestressed by a strong undulated spring
115. The opposite guiding strips 111 are prestressed again by oil pressure
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1~756~
varying to the square of tile crankshaft speed, but with a mechanical trans-
mittin6 device. This device consists of a half-moon shaped force-distributor
120 pushed against the rear s;de of the guiding strip 111 by a push rod 121,
the free end of which is cut at an angle to form an oblique end 122 which is
in contact with a small hydraulic piston 123, the end of which is cut at a
corresponding, complementary angle. This piston 123 and the push rod 121 are
cylindrica] and closely fitted in drillings of the rocking_piston 105, their
oblique ends 122 being sliding surfaces and therefore for instance hardened
and ground. The small hydraulic piston 123 can have sealing rings or the
like and is actuated by an oil column in a longitudinal hole 124 of the con-
necting rod 97. This oil column is put under pressure by its inertia in the
region of the top dead centre, this pressure being maintained in the region
of the lower dead centre by the non-return valve 125, as explained in Figure
1. The lower end of a longitudinal hole 124 is connected to the forced-feed
lubrication of the crank pin 91. Alternatively, it may be closed as in Fig-
ure 8. The longitudinal hole 124 is preferably formed by a steel tube 126
cast into the light-metal connecting rod 97, in order to prevent its undue
thermal lengthening which would affect the position of the rocking-piston
relative to the waisted cylinder. The drilling locating the small hydraulic
piston 123 is endwise closed, its oil leakages as well as the gas leakages
of the push rods 121 are evacuated downwards through a small venting port
127. The components 120 to 123 are symmetrically arranged and prestressed by
a coil spring 128.
With this hydromechanic piston guiding system, the prestressing of
the guiding and sealing strips 111 against the cylinder surface can be chosen
at will, independent of the oil pressure, simply by varying the angles of the
oblique ends 122. With a narrow angle of the oblique end 122 of the small
hydraulic piston 123, which however must not be self-locking, high force
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~75~8
multiplications can l)e achieved. As var;arlts, t:he small hydraulic piston
l2a n~ay be lengthened and have several oblique ends 122 to activate several
push rods 121, whereb~T the force distributors 120 can possibly be dispensed
with. Furthermore, the -.trong undulated spring 115 can be omitted, rendering
the prestressing system rigid. The same would be the case with syrnmetrically
oblique ends 122, i.e. Vee-shaped ends acting on push rods 121 on both guid-
ing and sealing strips 111, with the advantage that the automatic adjustment
of all wear takes place on both sides, i.e. sym~.etrically to the longitudinal
axis of the connecting rod 97.
The rocking-Eiston guiding and sealing corners 111, 112 are lubri-
cated by leaks of the encapsulated, forced-feed lubrication of the crankshaft
and/or by fresh-oil supply 130 arranged prefera.bly on the left side of the
waisted cylinder, because the sealing strips 112, due to their rocking move-
ment, always scrape the oil from left to right 5 when the engin~ rotat~s
clockwise.
According to Fig~reslO and 11, the two-stroke rocking-piston slide-
valve engine has an optimal reverse or loop scavenging with asymmetric timing
of inlet 131, transfer 132 and exhaust 133 with considerable aftercharge,
achieved by the rocking movement of the flat slides 106. With the narrow
rocking-piston 105, the area of the interface between the transfer 132 and
exhaust 133 gases is very small, so there is less interchange of heat and
reduced mixing of the gases and therefore more complete scavenging. This
engine is suitable as a petrol engine with carburettor, but a low-pressure
fuel injection, for instance according to the arrow 13~, would be particu-
larly attractive. Due to a comparatively low compression ratio and the
absence of hot valves, low-octane and lead-free petrol can easily be used.
9~ ' J`p ~J6/2 1 ,4~
- However, with a high compression ratio, a ~er1~ combustion
chamber 135, an injection nozzle 136 and a spark plug 137 arranged approx-
R ~ 9 --
75~
imntely as illus-trat,ed, multi-fuel running of the engine is possible. The
in~ection nozzle 136 has for instance three jets at right angles, two of
which are directed across the uniflow air-transfer 13O and one towards the
sparking plug 137. Even with this direct injection, the uniflow air-transfer
138 produces a soft increase of combustion pressure, thanks to the supply of
air continuing after top dead centre, therefore making for silent engine
running. The direct fuel injection can be replaced by a precombustion or
swirl chamber, which is suitable for Diesel or petrol operation with strat-
ified charge and whose communicating holes are again directed across the
uniflow air-transfer 13O.
At any rate, the rocking_piston offers new possibilities for fuel
mixing and combustion, whereby the absence of hot exhaust valves and the
inherent exhaust gas recycling strongly reduce the N0 content of the exhaust
gases. The comparatively hot exhaust, possibly fitted with portliners,
facilitates the afterburning of the CH. A further reduction of the exhaust
pollution can be achieved by adding a turbocharger or pressure wave machine,
which also increases the engine output.
As a variant~ Figures13 to 15 show a rocking_piston and connecting
rod assembly for a thermally highly loaded engine, for instance for mopeds
and motorcycles. Therefore, the rocking_piston 140 is an internally ribbed
steel forging to which a flat slide, preferably sta~.ped from chrome steel,
is spot welded. The connecting rod 142 is a steel forging as well and has
a non-split big end 143 with roller bearing attached to a fabricated crank-
shaft. The rocking-piston 140 is therefore screwed to the connecting rod
142 and can be withdrawn simply by dismantling the cylinder head. The exact
alignment between rocking-piston 140 and connecting rod 142 is assured by
flanges 144, and tight sealing of the flat slides 141 is achieved by pro-
jections 144 of the connecting rod 142 to which they abut.
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~ .
75~8
The double gllidine strips 11 are prestressed against the cylinder
wall through force-distriblltors 120 by two push rods 121 with oblique ends
122, each of which is actuated b~ the corresponding, complementary oblique
end of an actuating mass 1~5 arranged vertically. This actuating mass 145,
due to its inertia in the region of the top dead centre, causes the necessary
prestressing force on the guiding strips 111, which force automatically
increases, as required, to the square of the increasing engine speed. In the
region of the bottom dead centre, the actuating mass 145 is hindered from
falling back by oil pressure built up in the region of the top dead centre
and retained by a non-return valve 146 which is enclosed in a pocket 147
made, for instance, of P.T.F.E. material, as may be the ball 148. The pocket
146 is extended do~mwards through a passage in the housing 149 of the rocking-
piston to form a liguid reservoir 150 and is hermetically sealed at its bot-
tom end. This reservoir serves for re-adjustment of all wear and is put
under light pressure by a surrounding, elastic tube 151. The hydromechanical
rocking-piston prestressing device works in a different way to that in Figures
10 to 12, the prestressing force here being generated mechanically and sus-
tained hydraulically. Furthermore, it is independent of any oil supply and
confined to the rocking-piston, i.e. can easily be fitted and withdrawn with
it. It is completely leak-proof, arranged in comparatively cool zone of the
piston and allows a free choice of the liquid.
According to Figure 16, the guiding strips llla have no common dome
so that they slide against each other due to the rocking movement of the
piston 140. This sliding movement prevents the guiding strips llla and the
sealing strips 112 from sticking in their grooves and is made possible by an
oscillating member 155 being interposed between the guiding strips llla and
push rods 121 or force-distributors 120 shaped accordingly. The oscillating
member 155 is a semi-circular rod, the side of which abuts against the guid-
- 21 -
~s~
75~
ing strips llla and is not flat, but double-Vee shaped as shown in the draw-
ing. Obviously, the opposite groove of the rocking-piston 140 must have a
semi-circular base and an oscillating member 155 as well. Three guiding
strips llla are also possible, but with slightly different prestressing.
This is also the case in Figure 17 where four guiding strips lllb
are arranged in one groove, the intermediate two being actuated by the oscil-
lating member 155 slideable in an outer oscillating member 156 which actuates
the top and bottom guiding strips lllb. Such an arrangement, consisting of
eight identical guiding and sealing angles lllb/112b, with their abutting
ends alternatively arranged in different corners of the rocking-piston,
insures high gas-tightness between the rubbing surfaces of the guiding and
sealing strips lllb, 112b and the cylinder walls.
The variant according to Figure 18 has a solid or hollow guiding
roller 157 or needle located in a case 158 which is again actuated by push
rods 121. The guiding roller 157 or needle rotates at least partially on the
waisted walls of the cylinder inserts 76, 77, thus reducing friction and wear,
especially so when its bearing surface on the case 158 is partially running
on compressed gas.
Two or more guiding rollers 157 or needles may be arranged on top of
each other analogous to Figure 16 and 17. Such an arrangement seems to be
possible for example on the rocking-piston of a big or very big Diesel engine
having square cylinders and heads with four parallel valves and approximately
central fuel-injection and running in two-stroke or four-stroke cycle.
Figure 19 shows a particularly simple and versatile hydromechanical
device for prestressing rocking-pistons aga~`nst their circular, rectangular
or other convenient cylinder walls. This device can be incorporated in any
of the examples of execution mentioned above, but is here explained with
reference to Figures 2, 7 and 9. The piston crown 33, 59 can have a sealing
ring 13 or sealing strip 66 and a flexible partition plate 32, 60. The guid-
;.:
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75~
ing ring 15 or guiding strip 49 is prestressed against the cylinder wall by
the pressure tube 16, 62 which has a more or less cylindrical extension or
pocket 160 preferably central to the cylinder plane 2A and is filled with
liquid and closed at its ends in the region of the cylinder plane 2 A. The
interior diameter o~ the pressure tube 16 diminishes towards these ends in
order to reduce the hydraulic prestressing of the rocking-piston against
the cylinder wall in regions where practically no dynamic forces must be sup-
ported. Analogously, the same is the case with the pressure tube 62 which
has also a central pocket 160 and a small interior diameter on its short
sides with closed ends. The pockets 160 and therefore the pressure tubes
16, 62 are put under pressure by the inertia of a preferably cylindrical
acutating mass 161 of convenient high and specific weight in the region of
the top dead centre. This hydraulic pressure is maintained in the region of
the bottom dead centre by a hydraulic cushion closed by the non-return valve
162, of plastic material, under which again a liquid readjustment reservoir
164 is located, which may be prestressed for instance by a coil spring
located in an extension of the device housing 165 of the rocking-piston base
166. This pressure retaining device is again hermetically sealed in a pocket
167 made for instance in P.T.F.E. One or more of these devices 160 to 167
can be fitted to a rocking-piston and can easily be removed from above, to-
gether with the other wearing parts. By pulling the pocket 167 downwards,
the pressure in the tubes 16, 62 is released, making easy to fit the rocking-
piston 140 from above. The plugs 163, 148 and 23 should be lignt, for exam-
ple hollow or of foamed material, so that they float in the liquid in the non-
return valves.
The elements of the described examples of embodiment are normally
interchangeable with each other and are subject to detail modifications and
refinements, while still remaining within the scope of this invention. The
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5~
inventive rocking-piston prestressing devices are applicable to any type and
size of rocking-pistolltnachines. They may even be indispensible in tiny
rocking-pistons of, for instance, compressed-air motors for hand tools or
household refrigerator compressors, superseding the possible use of elastomer
0-rings behind the guiding and sealing elements, the efficiency of which
inevitably ceases over longer periods of time. Contrary to this, the inven-
tive hydraulic or hydro-mechanical rocking-piston prestressing device has
the unique advantage that the prestressing is reset under the influence of
inertia forces with every revolution of the machine, i.e. is regenerated
10 permanentlY-
As a last variant, especially suitable for tiny rocking_pistons as
mentioned above, the pressure tubes 16 snd 61, 62 can run directly on the
cylinder walls, their outer surface being strengthened and coated according-
ly. Tiny rocking-piston connecting-rod assemblies are provided as one-piece
plastic mouldings with a prestressing device somewhat as shown in Figures 8
and 19.
As already mentioned, for combustion engines, especially Diesel
engines, a layout somewhat according to FigureslO to 12 seems to be most
promising. This rocking-piston slide-valve engine has the same firing
interval, i.e. true running as a four-stroke engine with double the number
of cylinders and is extremely simple in construction and maintenance. Thanks
- to its inherent soft combustion, successive opening of inlet and exhaust
ducts, slap-free rocking-pistons with reduced oscillating masses, the absence
of gears, camshaft and ralves and thanks to a highly compact and rigid engine
housing, this engine may have unprecedentedly silent and smooth running with
low starting friction, low idling speed, low specific fuel and oil consump-
tion and low exhaust pollution. It is applicable as a stationary, boat or
light-aircraft engine as well as a prime mover for any kind of motor and
-- 2~ -
~7568
agricultural vehicle, mak;ng for substantial secondary advantages. For
instance, when fitted longitudinally or transversally to automobiles, it can
normally be arranged horizontally with a luggage comparatment above it ana
then can slide underneath the car in a crash, thus not shortening the crush
zones. According to Figure 10, the direction of rotation is preferably
clockwise, whereby the forces acting on the rocking_piston, i.e. its weight
and the reactions of the connecting rod big end friction and of eccentric
combustion pressure waves, due to an asymmetrically arranged combustion
chamber, all act on the same, lower cylinder wall, which makes for a stable
state, especially when starting.
As a particular example of adaptation, a two-cylinder, 1200 ccm
engine is installed in a safety car and represented in Figures 20and 21 in
elevation and plan view. Because of its extreme simplicity, light weight and
relative freedom from vibration, noise and maintenance, this rocking-piston
slide-valve engine 170 makes it practicable to adopt an underfloor, mid-
engine car layout which is not longer dominated, as hitherto, by the engine
installation, therefore giving spacious passenger and luggage compartments
and 70 cm crush zones at front and rear with an overall length of only 400
cm. After tilting the back seat 171 forwards and the protection shield 172
rearwards, the engine 170 as well as the accessories 173 and the conventional
automatic gearbox 174 are very accessible and can even be checked when the
car is on the move.- A primary gear reduction 175 drives a short, transversal
cardan shaft 176 and a very compact final drive 177 of a consequently light
rear axle 178 which is laterally guided by the transversal cardan shaft 1'76.
By choosing the ratios of the spur gears 175 and 177 and the length of the
trailing links 179 accordingly, the anticlockwise rotating, transversal
cardan shaft 176 produces the desired antidive effect. For dismantling, the
engine 170 can be supported and the right side of the car tilted upwards.
75~
Air-cooling ùirect to the up~er, hotter cylinder side can easily be achieved
by a centrifugal blower fitted to the free end of the crankshaft. A cross-
country reduction 175' and, thanks to the tyre-saving rigid axle 178, twin
tyres loO can be fitted.
Bigger cars, vans trucks and the like have an engine with three or
more cylinders and, if desired, a constant-velocity, sliding transversal
propeller shaft with separate lateral guiding of the axle 178, whereas very
small city-cars with three or four wheels have the back seat directly above
a centrally located engine and perhaps a standard gearbox with direct top
gear; otherwise, a chain-driven primary reduction 175 is necessary.
The rear-axle drive according to Figures 20 and 21 and variants can
be supplemented by a semi-automatic gearbox, a safety differential lock or a
uni~oint elastic axle according to earlier patents of the inventor. However,
this rear, axle drive is also of interest for orthodox, trunk-piston engines,
if necessary with a balance shaft l~l, or for any other type of suitable
motor.
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