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Патент USA US2108890

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Feb. 22, 1938.,
H. JÄNICKE
2,108,890
MOTOR COMPRESSOR OF THE FREE PISTON TYPE
Filed 001'.. 2, 1935
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2 Sheets-Sheet l
Feà. 22, 1938.
2108,89@
H. JÄNICKE
MOTOR COMPRESSOR OF THE FREE PISTON TYPE
Filed 0G12. 2, 1935
2 Sheets-Sheet 2
_Patented Feb. 22, 1938
UNITED sTATi-:sA PATE NT oFFlcE
2,108,890
yMOTOR. COMPRESSOR (ÈF THE FREE PISTOÑ
Y [-Hermann Jänicke,- Dessau (Anhalt), Germany,
assignor to Therese AJunkers, Gauting, near
' Munich, Germany
Application
October 2, ' 1935, serai N». ‘43,1'8'1.
In Germany October 16, 1934 ' 9 claims.
My invention relates to free piston motor com
pressors and more especially to that type. of en
gines of the kind aforesaid, in which the air com
5
(c1. 23o-5s)
driving free piston Imotor compressors, it is ini
portant to reach a predetermined end- tempera
ture of the compressed charging air, which, how
pressed in the compressor is utilized to drivev the ` ever, mainly depends from' the pressure ratio,
motor, forming part lof the mixture of gas and
air, or to scavenge the motor cylinder.
'
It is an object of my invention to improve this
type of motor compressor. In motor compres
sors, in which the pistons of the motor and the
10 compressor are rigidly connected With each-other,
.this possibility of keeping the pressure ratio in
v the motor at least approximately constant, is of .»
decisive importance for thev faultless operation.
of a free piston. motor compressor `of this type
regulatable within wide'limits.
f
The reduction ofthe discharge and delivery 10 "
forming a freely oscillating mass system,'it hasl pressures and in Iconsequence also of the motor
been suggested to regulate the compressor out ,pressures under partial loads at the same time
put at an approximately constant stroke of -the ‘ leads to a considerable reduction of the number
freely moving mass by varying the pressures of cycles of action per’unit of time, i. e. to a
15 (the suction pressure or the exhaust pressure or '
further regulation of output of the engine, so 10
both) prevailing in the compressor. It has also that comparatively small 'variations of pressure
been propose-d to feed the compressed air deliv
will give rise to considerable variations'of the
ered by the compressor, as a whole or partly, to lquantity of driving gasl delivered.
v
the motor as scavenging and charging air under l
-If the compressor piston has a larger diameter
20 a comparatively high pressure, the exhaust gases ' than the motor piston, there is provided on the
(gases of combustion and scavenging air in ex
cess) being fed to a secondary engine, for in
stance a piston engine or a turbine, to driveit.
According to this invention now the suction
5 and the delivery pressures in the compressor of
an engine of this type are varied for the purpose
of regulating the energy developed by the driv
ing gas furnished by the motor, and this in such
manner that the ratio between these two pres
30 -sures (which is hereinafter called the pressure
ratio of the compressor)` remains- at least ap
proximately constant.
This mode of regulation of such motor com
pressors has the effect that the pressure ratio
(scavenging and charging pressure: compression
end pressure) remains also at least approxi
mately constant. If for instance the suction
pressure in the compressor is reduced, while the l
pressure ratio of the compressor remains con
40
stant, the discharge pressure drops also corre
spcndingly. In consequence of the reduced pres
sures the feed-back energy liberated by the ex
pansion of the residual compressed air in the
dead space of the compressor becomes smaller
also during the return stroke; however, since
together with the discharge pressure of the com
pressor also the scavenging and charging pres
sures (and consequently the quantity) of the
motor charge (constant charging volume times
-density of the charge) had been reduced, the
reduced feed-back energy still suiïices to com
press this reduced quantity of motor charge at
about the same pressure ratio as hitherto pre
vailed in the motor. Since in motors with igni
55 tion by compression, as are used‘as a rule for
rear side of the compressor piston a differential
surface equal to the- diiference between the sur
face of the compressor piston and the surface
20
of the motor piston; the pressure acting on thisv
surface results, during the return stroke, in an 25
amount of energy taken up, by which the energy
available during the return stroke for the com
pressioni of the motor> charge is diminished.
Therefore if the amount’of the feed-back energy
liberated in the compressor varies in consequence 30
of regulating operations, the amount of energy
_taken up by the rear face of the compressory
piston must also be varied in the same sense in
order thatl the amount of energy available for Y
the compression of the motor charge enable this 35
compression to be carried through with >the de
sired pressure ratio which shall be kept approxi
mately constant. Therefore, in accordance with
this invention,- I further provide that the suction
pressure of the compressor which shall be regu 40
lated act on the rear face of the compressor
piston. This pressure may either act on the
piston unvariably asa constant load during the
entire stroke or it may form the lower or the
higher end pressure of a compression-expansion 45
line.
~
‘
I will now explain by invention in detail, hav
ing reference to the drawings annexed to this
specification and forming part thereof, which
illustrates in a purely diagrammatic manner an 50
engine embodying my invention by way of ex
ample.
In the drawings
f Fig. 1 shows a diagrammatic longitudinal sec
tion of a free piston motor compressor includ 55
2,108,890
2
ing two reciprocating free pistons, being one em
- bodiment of the present invention, while each
‘ of the Figs. 2 to 5 shows the pressure-volume
diagrams of the several compression spaces for
two regulation conditions.
Fig. 6 is a section of a modified form of a
‘separate control member.
Fig. ’I illustrates diagrammatically a modifica
tion being a free piston motor compressor in
10 cluding one reciprocating freevpiston, while
Fig. 8 is a longitudinal section, drawn to a
larger scale, through the motor cylinder shown
in Fig. 7.
-
Referring to the drawings, I is the motor cylin
15 der, in which operate two pistons 2, 2 moving in
opposite directions; each of these motor pistons,
one of which controls the scavenging ports 3,
the other one the exhaust ports 4, is rigidly con
nected with the compressor piston 5. The com
20 pressor pistons operate in compressor cylinders 6
arranged coaxially to the motor cylinder I and
provided with suction valves 1 and pressure
valves 8.
When the two freely moving masses 2,5 have
4 are fed to a secondary engine, for instance a.
turbine (not shown) to do useful work therein.
For the purpose of regulating the quantity and
amount of energy in the driving gas furnished by
the driving gas generator, the suction pressure p1
and delivery pressure p2 in the compressor are
varied. For the variation of the suction pressure
there is for instance provided at each suction
chamber I8 of the compressor a slide I2, which is
adjustable manually or automatically, for in 10
stance inv dependency from the load on the
secondary engine. 'I'his is shown in Fig. 1, in
which the centrifugal governor 40 of a secondary
engine (not shown) is provided with a sleeve 4I,
to which corresponding to the two slides I2 to
ward both sides two rods 42, 43 are linked. The
other ends of these rods are linked to the free
ends of the legs 44, 45 of the bell cranks arranged
for rotation about the points 46, 41. The free
ends of the legs 48, 49 of the bell cranks are 20
llinked to the rods 50, 5I. These rods 50, 5I are
connected through the fulcrurns 52, 53 with the
rods 56, 51 guided at 54, 55, these rods being .di
rectly connected to the slides I2. The positions
25
25 approached each other and when the quantity * of the governor and the rods, shown in full lines,
of charging air enclosed between- the motor pis
tons 2 is compressed, fuel is injected into the air
through the nozzle 9. Theregulation by means of
a fuel pump of the quantity of fuel to be supplied
30 to the motor may take place e. g. in a well known
manner in dependency of a pressure gas con
tainer, as described in- detail e. g. in the de
scription of Fig. 1 of applicant’s copending U. S.
application Ser. No. 710,483. Such container may
35 be connected to conduitI I0 after the compressor
portion of the free piston engine according to the
present invention in a manner such that from
this container the scavenging air passes into the
motor cylinder. On the other hand, a pressure
gas container might also be connected to the
conduit 30 so that the secondary engine is sup
plied from this container. -The gases of com
bustion generated in the combustion, which now
sets in, force the freely moving masses apart
45 (working stroke). In consequence thereof there
first takes place a compression of the charge en
closed in the compressor cylinders from the pres'
sure pi to pressure p2 along line AB and
thereafter the discharge of the compressed air
along line BC (Fig. 2). After the scavenging and
50
exhaust ports 3, 4 have been uncovered by the
motor pistons 2, the freely moving masses come
to a standstill. The residual compressed air in
the dead spaces of the compressor cylinder 6, on
55 which acts the pressure p2, in expanding along
line CD (Fig. 2) down to the suction pressure p1,
now forces the freely moving masses again to
wards each other (return stroke), while at the
-same time (line DA) fresh air is sucked through
60 the suction valves 1 into the compressor cylin
ders. The compressed air discharged during the
working stroke through the pressure valves 8
flows through the pipe I0,‘after the scavenging
ports 3 have been uncovered by one of the motor
pistons 2, into the motor cylinder I, at the same
time displacing the exhaust gases through the
exhaust ports 4 and filling the motor cylinder
with fresh air under the pressure pz. In the ex
haust gas conduit I I communicating with the ex
haust ports 4 of the motor is provided a pressure
regulating member' 2U, which determines the
scavenging pressure in the motor and conse
quently also the discharge pressure pz in the com
pressor. The waste gases and the scavenging air
75 in excess discharged through the exhaust ports
illustrate the positions with higher numbers of
rotation, i. e. with smaller load on the secondary
engine, while on the left hand side of the gover
nor the dashed lines indicate the positions of the
governor sleeve and the rods with smaller nurn 30
bers of rotation, i. e. with higher load on the
secondary engine. In the latter case e. g. the
fulcrum 52 has been displaced toward 58. About ,
the length of this distance 52-‘58 also the slide
has been lifted. Hereby the throttling of the suc
,
tion air has been reduced in a manner such that
a higher output of the compressorportionand also
of the motor portion of the free piston engine
is effected'. When the inlet is throttled, i. e. when
the suction pressure p’i is low, there is obtained 40
the compressor diagram A'B'C'D’A' drawn with
dash lines in Fig. 2, with the delivery pressure
p'z. The variation of the delivery pressure in
such manner that the pressure ratio inthe com
pressor remains approximately constant, is ef
fected by means of the pressure regulating mem
ber 20 provided in the conduit II, which is illus
trated in section in Fig. 6. The waste gas conduit
II is closed by a slide 22 formed with a passage
.2I, and operated by a piston 23. The gases in
the conduit II pass through a boring 24 below
the lower ring-shaped piston surface 25, so that
this surface is acted upon by the pressure of
the combustion gases escaping from the motor
cylinder and of the scavenging air in excess, i. e. 55
with the pressure pz or p’z, while the upper sur
face 26 of the piston 23 is placed under the suc
tion pressure p1 or p’i, since the space above the
piston 23 is connected through pipes 21, I1 with
the suction chamber I8. The atmospheric pres
60
sure acting on the slide face 28 is counteracted
by the spring 29 acting from above on the piston
23, this spring being so dimensioned that a small
excess of force tends to shift the pressure regu
lating member 22, 23 downwardly into closing 65
position. The surface ratio of the two surfaces
24 and 2S is so chosen that on the pressure p2
being attained, the pressure regulating member is
lifted counter to the pressure p1 on the piston
surface. However, if the suction pressure p1 70
is throttled, for instance down to p'i, the cor
respondingly lower delivery pressure p2 suffices
already to open the pressure regulating member,
so that thus the ratio of the pressures 1712172 re
mains always approximately constant, since the 75
2,108,890
3
surface ratio is approximately in the reversed
between the throttle slide I2 and the suction n
vproportion of these pressures.
valves 1.
The waste gases and the scavenging air, in ‘
Instead of placing on the differential surface
excess, flow through‘the piping 30 to the second
I3 a load which remains equal throughout the>
ary engine, for instance a turbine, (not shown).
stroke, according to line LM or L’M’, I may also
In the diagram according to Fig. 2 the feed rplace thereon a load which changes, according
back energy, which is liberated in the compressor f to certain laws, for instance an alternatingcom
pression and expansion‘of the gas in the. space
cylinder and brings about the return stroke, is
represented at a high suction and delivery pres-y
10 sure of the compressor by the surface CDAFEC
and, in the case of the reduced pressures p'i, p'a,
by the considerably smaller surface C’D’A'FEC'.
According to Fig. 3 the compression in the motor
cylinder begins in the f'lrst‘case (high compressor
15 pressures) at the pressure pz andends at the
pressure 123, the compression work is represented
by the surface GHJKG; in the second case the
compression in the motor cylinder begins at the
lower pressure p'z and endsÀ at the pressure p'a;
20 in correspondence therewith also a lower com
I4 according to Fig. 5 which follows the line LQ
for theñrst, and the line L'Q' for the second 10
of the two regulating instances mentioned above.
To this end there is connected with the com
pressor piston 5 a slide I9 which uncovers an
aperture I6 formed in the cylinder wall, which .
communicates with the suction chamber I8
through the conduit I"I, when the freely mov
.ing mass has reached its extreme'iend positionv
(between the end of the working stroke and the
start for> the return stroke). I thus obtain that
in this end position the same pressure prevails
pression energy corresponding to the surface in the space I4 as inthe space I8; on the aper 20
G'H’JKG’ must be brought _into action.; Thus tures I 6 having been closed, when the return
the compression ratio inthe motor (in the first Astroke begins, there now takes place a compres
case parpz and in the second case p'3:p’2) is at sion in the Vspace I4 according to vline LQ or
25 least approximately equal in both- cases, i. e. it
i o remains practically constant during all variations
of the initial compressor pressure.
When the compressor piston 5 has a larger
diameter than the motor piston 2, so~y that on
30 the rear side‘I3 of the compressor piston 5 there
remains over an effective piston surface equal to
the difference between the compressor piston sur
face and the motor piston surface, this differen
tial surface must, during the return stroke, pro
L’Q’, while during each subsequentv working
stroke an expansion takes place along they-same
line.
-
' In the example just described the suction pres
:ure :v1 in the compressor thus‘forms the lower
end pressure (point L or L’) of the compression 30
expansion line for-the space I4. Instead of this,
also one ofthe regulating pressures (either the v v
suction pressure pi or the delivery pressurepz) ‘
may form the upper end pressure of a compres
sion-expansion line. In that case the aperture 35
tracted from the feed-back energyCDAFEC líb
I6 should be controlled in such manner that the '
erated in the compressor cylinder, in order to space
I4 communicates with the space I8 through
obtain the energy still available for the com-` conduit I'I not, as above, during the outer dead
pression of the motor charge. In order now, that centre position of the piston (between thefend
40 in regulating steps i. e. when varying the pres
of the working stroke and the start of --the return 40
35 duce a displacement energy, which must be sub
sures arising in the compressor and the feed-back _ stroke), but duringtlie inner dead centre posi-energy to be produced by the compressor, the tion (between the end of the return stroke and
` permanently constant pressure ratio in the motor
the start of the working stroke). However, if
be attained, I load also the diil'erential surface the delivery pressure p2 is chosen as end pres
45 with a regulatable pressure, for instance the suc
tion pressure of the compressor.
In the two
instances of regulation here in vview there now
result, according to Fig. 4, different amounts of
displacement energy to be produced by the dif
50 ferential surface, viz. in the first case (loading
with the compressor suction pressure p1) the
amount represented by the surface LMNOL, in
the second casel (loading by the compressor pres- j
sure p’i) the amount corresponding to the sur
55 face L’M’NOL’. There are therefore available as
feed-back energies:
v
In the ñrst case:
surface CDAFEC-surface LMNOL:
surface GHJKG
60
and
In the second case:
-
,
surface C’D’A’FECf-surface L'M’NOL’:
65
'
-
surface G'H'JKG
Since the amounts of energy to be deducted
(LMNOL and L’M’NOL’) vary in thesame pro
portion as the amounts of energy liberated in the
compressor, the pressure ratio in the motor
70 (pztpa) remains at least approximately constant.
In order to realize this mode of operation, it is
only necessary, in the arrangement according to
Fig. l, to bring the spa-ce I4 covered by the dif
ferential surface I3 into permanent communica
v75 tion, by means of a conduit, with» the space I8
sure, then during theinner dead centre position 45
the space I4 must be made to communicate with
the delivery conduit I0 of the compressor.
The quantity of fuel to `be fed per cycle into-
_the motor cylinder through the nozzle 9, should
be chosen in accordance with the `quantity of air, 50
which is regulatable according 'to thisA invention,
in the motor cylinder. 'The Aregulation of _the
quantity of fuel may also be inñuenced‘in a well
known manner in dependency fromthe regulat
ing pressures (suction pressure p1 or delivery 55
pressure p2).
l
Fig. 7 illustrates diagrammatically a free pis
ton motor compressor provided with a single re
ciprocatory free piston, the same reference nu
merals being used as in Fig. 1. According to Fig. 60
’7, a buffer or compensating cushion chamber is
provided, which comprises the piston 35 and the `
cylinder space 36. The space 36 constitutes a
boring in the reciprocatory free piston 2, 5, while
the piston 35 is stationary. The movement of 65.
the free piston 2, 5 causes the content of the
cylinder space 36 to be alternately compressedand expanded. 'I'he amount of energy stored in
this manner in the buffer space 36 during the
working ,(upward) stroke> of the motor piston 2
is again delivered during the return (downward)
stroke of the piston to the free pistons, vin a
manner known in itself, for the purpose of sup
plementing the amount of energy deriving from
the dead space of the compressor.
75
:5,106,890
4
Fig. 8 shows a longitudinal section, drawn to a
larger scale, through the motor cylinder i shown
in Fig. 7. `The reference numerals are the same
as in Fig. 7. Two slots 3 are provided as inlet for
Cî the compressed air, while the combusted gases
are delivered from the motor cylinder space iirst
through the preliminary delivery slots 4' and
subsequently through the main delivery slots 4.
There are shown two of each of these delivery
10 slots. The inlet and delivery slots are controlled,
in a known manner, by means of the motor pis
ton 2. T’ne arrows shown in Fig. 8 represent the
direction of current of the compressed air or the
combusted gases, respectively.
15
I wish it to be understood that I do not desire
to be limited to the exact details of construction
shown and described for obvious modifications
20
pressure prevailing in said compressor to act on
the rear face of said compressor piston, means
for conducting compressed gas from said com
pressor cylinder into said motor cylinder, means
for varying the suction and delivery pressures
in said compressor cylinder, while keeping the
ratio of the two pressures approximately con
stant, and means for causing the pressure pre
vailing in the part of said compressor cylinder
covered by the rear side of said compressor piston 10
to vary according to a compression-expansion
line, the end pressure of which is determined by
one of the pressures prevailing in said compres
SOI'.
5. A free piston motor compressor comprising 15
in combination, a motor cylinder, a compressor
cylinder and free pistons rigidly connected with
will occur to a person skilled in the art.
each other and arranged in said cylinders »for
free reciprocation, said motor cylinder being
1. A free piston motor compressor, iny which
the compressed air produced in the compressor
formed with an exhaust port, an exhaust gas 20
conduit arranged to the rear of said exhaust
ports, a regulating device inserted in said con
serves as scavenging and charging air for the
motor, comprising in combination, a motor cyl
inder, a compressor cylinder, a free piston- in said
25 motor cylinder and a free piston in said compres
sor cylinder, said pistons being rigidly connected
_with each other, means for conducting com
pressed gas from said-compressor cylinder into
said motor cylinder and means for varying the
30 suction and delivery pressures in said compressor
cylinder, while keeping the ratio of the two pres
sures approximately constant.
'
'
2. A free piston motor compressor comprising
in combination, a motor cylinder, a compressor
35 cylinder, a free piston in said motor cylinder and
a free piston in said compressor cylinder, said
pistons being rigidly connected with each other,
said compressor piston having a larger diameter
than said motor piston, means for causing the
40 suction pressure prevailing in said compressor to
act on the rear face of said compressor piston,
means for'conducting compressed gas from said
compressor cylinder into said motor cylinder and
means for varying the suction and delivery pres
45 sures in said compressor cylinder, while keeping
the ratio of the two pressures approximately
constant.
,
~
‘
3. A free piston motor compressor comprising
in combination, a motor cylinder, a compressor
50 cylinder, a free piston in said motor cylinder and
a free piston in said compressor cylinder, said
pistons being rigidly connected with each other,
said compressor piston having a larger diameter
than said motor piston, means for causing the
55 suction pressure prevailing in said compressor to
act on the rear face of said compressor piston,
means for conducting compressed gas from said
compressor cylinder into said motor cylinder,
means for varyingthe suction and delivery pres
60 sures in said compressor cylinder, while keeping
the ratio of the two pressures approximately
constant, and means for causing the pressure
prevailing in the part of said compressor cylin
der covered by the rear side of said compressor
65 piston to vary according to a compression-expan
sion line, the initial pressure of which is deter
mined by one of the pressures prevailing in said
compressor.
4. A free piston motor compressor comprising
in combination, a motor cylinder, a compressor
cylinder, a free piston in said motor cylinder and
a free piston in said compressor cylinder, said pis
tons being rigidly connected with each other, said
'compressor piston having a larger diameter than
75 said me or piston, means for causing the suction
duit, a piston-shaped control member forming
part Iof said device and formed with two piston
surfaces, one surface being adapted to be acted 25
upon by one, the other surface by the other reg
-ulating pressure arising in said engine, these con
trolling surfaces being dimensioned at a ratio
which is approximately the reverse of the ratio of
30
said regulating pressures.
6. A free piston motor compressor comprising
in combination, a motor cylinder, a compressor
cylinder and freel pistons rigidly connected with
each other and arranged in said cylinders for
free reciprocation, said motor cylinder being 35
«formed with an exhaust port, an exhaust gas
conduit arranged to the rear >of said exhaust
ports, a regulating device inserted in said con
duit, a piston-shaped control member forming
part of said device and formed with two piston 40
surfaces, one surface being adapted to be acted
upon by one, the other surface by the other reg- ,
ulating pressure arising in said engine, these con
trolling surfaces being dimensioned at a ratio
which is approximately the reverse of the ratio 45
of said regulating pressures, and means whereby
the space in said compressor cylinder covered
by the rear face of said compressor piston is ar
ranged to be permanently acted upon by the
suction pressure in said compressor.
50
7. A free piston motor compressor comprising
in combination, a motor cylinder, aV compressor
cylinder and free pistons rigidly connected with
each other and arranged in said cylinders for
free reciprocation, said motor cylinder being 55
formed with an exhaust port, an exhaust gas
conduit arranged to the rear of said exhaust
ports, a regulating device inserted in said con
duit, a piston-shaped control member forming
part of said device and formed with tw-o piston 60
surfaces, one surface being adapted to be acted
upon by one, the other surface by the other of
the regulating pressure arising in said engine,
these controlling surfaces being dimensioned at
a ratio which is approximately the reverse of the 65
ratio of said regulating pressures, and a con
trolling member connected with said pistons and
connecting the space in said compressor cylinder
covered by the rear face of said compressor pis
ton during the outer dead centre position of said 70
piston with the suction space of said compressor.
8. A free piston motor compressor comprising
in co-mbination, a motor cylinder, a compressor
cylinder and free pistons rigidly connected with
each other and arranged in said cylinders for 75
2,108,890
free reciprocation, said motor cylinder being
formed with an exhaust port, an exhaust gas
conduit arranged to the rea_.r of said exhaust
ports, a regulating device inserted in said con
duit, a piston-shaped vcontrol member forming
part of said device and formed with two piston
surfaces, one surface being adapted to be acted
upon by one, the other surface by the other
regulating pressure arising in said engine, these
10 controlling surfaces being dimensioned at a ratio
which is approximately the reverse of the ratio
of said regulating pressures, and a control mem
ber, which connects the space in said compres
sor cylinder covered by the rear face of said
15 compressor piston during the inner dead centre
position of said piston with the suction space of
said compressor°
9. A free piston motor compressor comprising
in combination, a motor cylinder, a compressor
20 cylinder' and free pistons rigidly connected with
5
each other and arranged in said cylinders for
free reciprocation, said motor cylinder being
formed with an exhaust port, an exhaust gas
conduit arranged to the rear of said exhaust
ports, a regulating device inserted in said con
duit, a piston-shaped control member forming
part of said device and formed with two piston
surfaces, one surface being adapted to be acted
upon by one, the other surface by the other reg
ulating pressure arising in said engine, these 10
controlling surfaces being dimensioned at a ratio
which is approximately the reverse of the ratio of
said regulating pressures, and a control member,
which connects the space in said compressor
cylinder covered by the rear face of said com 15
pressor piston during the inner dead centre posi
tion of said piston with the delivery conduit of
the compressor.
HERMANN JÄNICKE.
20
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