EP2860346A2 - Motor with pistons moving in a piston guiding channel - Google Patents

Abstract

Proposed is an engine with a fixed, annular and at least partially closed by a piston guide channel wall (3) trained piston guide channel (1) in the piston guide channel (1) in a row with fixed distance to each other moving piston (2.n), wherein between the piston (2.n, 2.n-1) in each case a working space (4) is formed and the volume of the work spaces (4) successively and cyclically when passing through the piston guide channel (1) changed by at least after a section with a continuous volume reduction ( 5.1) is followed by a section of constant or slightly increasing volume (5.2) followed by a section with a continuous increase in volume (5.3) of the respective working space (4) and this volume change cycle starting after a section for expelling (5.4) the expanded gases reconnects with a volume reduction.

Description

In particular, the invention relates to a motor with a piston guide channel and pistons which move in succession in the piston guide channel and which are driven by gas expansion.

The reverse operation, namely an external drive, can also compress gas.

Such motors are known in the embodiment as ring piston machines.

The piston engine after DE 102009 040 270 A1 consists of two piston carrier rings, on which pistons are arranged on the outer edges per piston carrier ring. All pistons move in a cylinder (torus) bent into a circular ring. The piston shape corresponds to the cylinder shape. Each piston carrier ring is provided inwardly with a toothing, which are coupled to each other such that in a total rotating movement, a relative movement of the piston takes place to each other, so that the working spaces between the pistons increase and decrease. This is the clocks of the engine (suction, compression, working, ejection) adapted, with the suction and ejection takes place via slots.

The DE 19 624 257 C2 describes an engine having an annular cylinder formed around an orifice and having a reciprocating piston in the annular cylinder, wherein in the annular cylinder, a partition wall is arranged, the annular cylinder in an air intake and Compression chamber and divides into a combustion chamber, so that as the reciprocation of the arc piston in one of the chambers, the volume expands, while the other chamber reduces its volume. Such engines are commonly referred to as swing piston engines.

Moreover, it is known to change the compression ratio in piston engines by changing the position of the piston to the connecting rod ( DE 10 2011 115 417 A1 ).

What these engines have in common is that they only have a short period of time and a limited volume for gas expansion, so that a lot of energy is lost.

The object of the invention is to propose a motor which makes maximum use of the expansion of the gases. This object is achieved with the features of claim 1. Advantageous embodiments are the subject of the dependent claims.

The engine according to the invention has at least one piston guide channel and in the at least one piston guide channel successively moving piston, which are driven by a gas expansion, wherein the at least one piston guide channel is fixed, annular and at least partially closed by at least one piston guide channel wall formed between the adjacent and in each case a working chamber is formed in each case in the at least one piston guide channel moving piston by the pistons are fixed coupled to each other at a fixed distance and sealingly abut with their piston portions in the region of the work spaces at the at least one closed piston guide channel wall wherein the volume of the work spaces is changed successively and cyclically as it passes through the at least one piston guide channel by at least after a section with a continuous volume reduction is followed by a section of constant or slightly increasing volume, followed by a section with a continuous increase in volume of the respective working space, where most of the gas expansion takes place and this volume cycle reconnects to a section for expelling the expanded gases, beginning with a volume reduction.

In the ejection section, the pistons are at least guided. This can be done by the partially open at least one piston channel wall or by separate guides.

The portions having a volume reduction, a constant or slightly increasing volume and an increasing volume of the working spaces are preferably arranged in a straight portion of the annular piston guide channel or the at least one annular piston guide channel is circular in its longitudinal extent.

As expanding gases are all known fuel gases and fuel-air mixtures in question, which are preferably introduced into the work spaces through slots or produced in the workrooms, for. by injecting fuel into compressed air.

Pistons, as used herein, are bodies on which an expanding gas in a piston guide channel exerts pressure and thereby is set in motion, or vice versa, which are moved from the outside and compress gas when moving through the piston guide channel.

Longitudinal direction follows the piston guide channel. The piston guide channel axis is the axis about which the piston guide channel is disposed. The gas expansion can be made in various ways, for. B. by a heating gas is introduced, a compressed fuel air mixture is ignited, ignited outside the engine ignited gas, etc. In a first embodiment, the piston guide channel circumferentially in the merging sections of the volume change of the working spaces changed or changeable cross-sections, to which the adjust the piston guide channel walls sealingly abutting piston sections of the piston, d. H. the cross section of the pistons changes.

In this case, the cross section of the piston guide channel is formed in its greatest extent by a square or rhomboid surface and in the smallest extent by a rhomboid slot.

The piston guide channel can be made rigid or the cross section of the piston guide channel can be enlarged or reduced by a force from the outside. The latter requires that the piston guide channel walls are assembled like a hinge.

In a preferred embodiment, the portions having a volume reduction, a constant or slightly increasing volume and an increasing volume of the working spaces are arranged in a straight portion of the annular piston guide channel. For the aforementioned piston guide channel suitable pistons are collapsible and have in the unfolded state, the shape of a bottom-open square pyramid with a square or rhomboid bottom cross-section and hingedly connected pyramid edges.

Preferably, the pistons engage at least in the region of a pyramid bottom side corner with a guide element in a guide in the piston guide channel.

In a second embodiment, a piston carrier ring is arranged in the at least one piston guide channel, which is driven by the piston performs a movement in the longitudinal direction of the piston guide channel, wherein the piston relative to the piston carrier ring or vice versa slidably disposed and the volume change of the working spaces by continuously changing distances between the Piston carrier ring and the respective working space final piston guide channel wall section is executable, whereby the piston carrier ring in the region of the working spaces sealingly abuts the piston guide channel wall.

Preferably, the piston guide channel in the closed piston guide channel section on two parallel sections of the piston guide channel wall, which are interconnected by the final piston guide channel wall portion.

The change in distance between the piston carrier ring and the respective working space final piston guide channel wall portion is in the following manner feasible: by an inclination of the final piston guide channel wall portion relative to the piston carrier ring and / or by a change in position of the piston carrier ring in the piston guide channel.

At an inclination of the final piston guide channel wall portion, the pistons are arranged in transverse recesses of the piston side located in the piston guide channel piston carrier ring.

Preferably, the piston guide channel is annular in its longitudinal extension, wherein the axis of rotation of the piston carrier ring coincides with the piston guide channel axis. The piston carrier ring height should be constant.

An advantageous further development provides that the piston channel bottom of at least one piston guide channel has the reverse inclination to the piston carrier ring as the piston piston channel end portion opposite the piston carrier ring, so that "piston guide channels" are formed on both sides of the piston carrier ring, the piston carrier ring being movably supported in a longitudinal guide of the thus formed piston guide channel is and the piston carrier ring has continuous transverse slots, in each of which a piston slidably guided by and sealed to the two opposite piston piston ring the piston guide channel wall sections is arranged so that the pistons form closed working spaces on both sides of the piston carrier ring.

In order to ensure a round motor, the direction of displacement of the piston in the piston carrier ring is preferably parallel to the axis of rotation of the piston carrier ring.

In the variant with the change in position of the piston carrier ring in the piston guide channel, the piston carrier ring consists of mutually coupled plates which at least in the sections with a reduction in volume, a constant or slightly magnifying volume and an increasing volume of the work spaces sealed the piston guide channel in a piston guide channel to form the work spaces and a piston guide channel in which slide the plates penetrating piston supported or unrolled.

The plates are movably supported on or in longitudinal guides of the piston guide channel, the longitudinal guides being arranged to vary the plate spacing from the final piston guide channel wall section for the purposes of volume reduction, a constant or slightly increasing volume and an increasing volume of the working spaces.

A movement of the piston thus takes place substantially only in the longitudinal direction of the piston guide channel, wherein in each case when changing from the reduction in volume to a constant or slightly magnifying volume and an increasing volume of the working spaces and vice versa a slight pivoting movement is performed when the angle of attack of the piston to the plates is not changeable. By appropriate adjustments of the Piston guide channel bottom and / or the rolling or sliding support of the piston and / or the seals of the piston on the piston guide channel wall this can be compensated, so that abut in the region of the working chambers, the piston each sealingly against the piston guide channel wall.

In a preferred embodiment in this variant, the guides for the plates are arranged outside the piston guide channel. They are thus outside of the immediate combustion chamber, which is advantageous for the selection of materials and the specific design of the guides.

Each adjacent plates are sealed to each other and hinged together.

The output of the motors is arranged in an at least partially open portion of the piston guide channel. Preferably, several outputs are provided.

Fig. 1:

eine Prinzipskizze des Motors mit zusammenklappbaren Kolben in einer Draufsicht,

Fig. 2:

den Motor gemäß Fig. 1 im Schnitt,

Fig. 3:

in einer Draufsicht den Motor mit verschiebbaren Kolben in einem kreisringförmigen Kolbenführungskanal,

Fig. 4:

einen Schnitt durch den Motor aus Fig. 3,

Fig. 5:

einen Schnitt durch den Motor aus Fig. 3,

Fig. 6:

eine Motorausführung mit beidseitig eines Kolbenträgerringes vorhandenen Arbeitsräumen,

Fig. 7:

einen Schnitt durch den Motor nach Fig. 6,

Fig. 8:

eine Prinzipskizze der Seitenansicht des Motors mit einem geführten Kolbenträgerring,

Fig. 9:

einen Querschnitt von Fig. 8.

The preferred engine designs will be explained with reference to the drawings. Show it:

Fig. 1:

a schematic diagram of the engine with collapsible piston in a plan view,

Fig. 2:

the engine according to Fig. 1 on average,

3:

in a plan view of the motor with displaceable piston in an annular piston guide channel,

4:

a cut through the engine Fig. 3 .

Fig. 5:

a cut through the engine Fig. 3 .

Fig. 6:

an engine version with working spaces on both sides of a piston carrier ring,

Fig. 7:

a cut through the engine after Fig. 6 .

Fig. 8:

a schematic diagram of the side view of the engine with a guided piston carrier ring,

Fig. 9:

a cross section of Fig. 8 ,

Fig. 1 and Fig. 2 show in schematic diagrams of the engine with collapsible piston 2.1 - 2.4 in the piston guide channel 1 in a plan view and in section AA. Section AA is limited to the sections 5.1 - 5.3, in which a volume change of the working space 4 is made.

The piston guide channel 1 is fixed, annular and executed in sections 5.1 - 5.3, in which a volume change of the working spaces 3 is performed, closed by piston guide channel walls 3.

The sections 5.1 - 5.3 with a volume reduction, a constant or slightly increasing volume and an increasing volume of the working spaces 4 are arranged in a straight portion of the annular piston guide channel 1.

In the section for discharging 5.4 of the pistons 2.1 -2.n moving expanded gases, the pistons are 2.1 - 2.n guided by piston guides 6, 7. In this section, the ring of the piston guide channel 1 is closed in each case.

The piston guide channel 1 has circumferentially in the merging sections 5 of the volume change of the working spaces 4 modified cross-sections, to which adapt to the piston guide channel walls 3 sealingly abutting piston portions of the piston 2.1 - 2.n.

The cross-section of the piston guide channel 1 is in its largest dimension (section CC, section DD) a square or rhomboid surface and in the smallest dimension a rhomboid slot (section BB).

In the illustration, the cross section of the piston guide channel 1 is rigid. Also provided is an embodiment, where the cross section of the piston guide channel 1 can be enlarged or reduced by a force from the outside.

The successively moving piston 2.1 - 2.n, which are driven by a gas expansion, form pairs of work spaces 4 by the pistons (2.1 / 2.2, 2.2 / 2.3, 2.3 / 2.4, etc. are arranged coupled to each other at a fixed distance and in the area of the working spaces 4 with piston portions on the piston guide channel walls 3 sealingly abut.

As a coupling between adjacent pistons 2.1 / 2.2, 2.2 / 2.3, etc. can each serve in the center of the piston articulated rods.

The volume of the working chambers 4 changes sequentially and cyclically when passing through the piston guide channel 1, by the section with a constant volume reduction 5.1 is followed by the section with constant or slightly magnifying volume 5.2, the section with a continuous increase in volume 5.3 of the respective Working space 4 follows. The expansion of the gases takes place beginning at the end of section 5.2 or entering section 5.3 and continues in section 5.3. In the illustration, this concerns the working space between the pistons 2.3 and 2.4 and 2.4 and the piston no longer shown before 2.4.

The gas expansion can be made in various ways in which burning gases are introduced from the outside starting in section 5.2 by compressed air in the working space 4 between the pistons 2.1 and 2.2 and fuel is injected in section 5.2 and an ignition to the end of section 5.2 Thus, an engine once set in rotation by a starter will continue its orbital motion through the following gas expansion repeating from workspace to workspace, respectively in the area of end 5.2 - 5.3.

These statements apply at least analogously to those in the following Fig. 3 - 9 described motor or compressor designs.

The volume change cycle recurs after a section 5.4 for expelling the expanded gases, beginning with a volume reduction.

The pistons used 2.1 - 2.n are collapsible and have in the unfolded state in the form of a bottom-open square pyramid with a square or rhomboid bottom cross-section, the pyramid edges 8 are hingedly connected.

In the illustrated embodiment, the pistons 2.1 - 2.n In the region of two opposite pyramid bottom side corners guide elements 9 for guides in the piston guide channel 1. These can also interact with the guides 6 and 7 in section 5.4.

The output 11 of the motor takes place in the at least partially open section 5.4 of the piston guide channel 1, since the moving parts are accessible z. B. in the driver on the piston 2.1 - 2.n engage one after the other in a driven pinion.

The in FIG. 3 to FIG. 5 shown motor has a piston guide channel 1, which is annular in its longitudinal extension and at least in the closed piston guide channel section has two parallel piston guide channel wall sections 3.2, which are connected by a piston guide channel wall section 3.1.

In this engine as well, the piston 2.n, which moves in succession in the piston guide channel 1, are driven by gas expansion, as described above using the example of FIG Fig. 1 and 2 ,

Between the adjacent and successively in the piston guide channel 1 moving piston 2.n, 2.n-1 each of the working space 4 is formed by the pistons 2.n, 2.n-1 are arranged coupled to each other at a fixed distance from each other and in the Working spaces 4 with piston sections abut sealingly on the piston guide channel wall 3, wherein the volume of the working chambers 4 successively and cyclically changed when passing through the piston guide channel 1 by 5.1 after the section with a steady volume reduction Section follows with a constant or slightly increasing volume 5.2, followed by the section with a continuous increase in volume 5.3 of the respective working space 4 and this volume change cycle after the section expelled 5.4 of the expanded gases again connects with a volume reduction.

The ejection section 5.4 is substantially open, the pistons 2.n being guided by guides 6, 7.

The coupling of the piston 2.n is carried out here by a arranged in the piston guide channel 1 piston carrier ring 12. The piston carrier ring 12 is offset by the piston 2.n in a rotational movement in the longitudinal direction of the piston guide channel 1, wherein the rotational axis 13 of the piston carrier ring 12 coincides with the piston guide channel axis 14.

The piston carrier ring 12 is arranged on the bottom side in the piston guide channel 1 and has a constant height.

The pistons 2.n are slidably disposed in the piston carrier ring 12 in transverse recesses 16 of the piston carrier ring 12.

The change in volume of the working spaces 4 is performed by continuously changing distances between the piston carrier ring 12 and the respective working space inclined to the piston carrier ring 12 arranged piston guide channel wall section 3.1, the piston 2.n in the working space 4 sealingly against the piston guide channel wall 3 by the Piston 2.n out of the piston carrier ring 12 out or in this be pushed into it. Likewise, the piston carrier ring 12 is sealed against the piston guide channel wall 3.

The direction of displacement 15 of the pistons 2.n in the piston carrier ring 12 is parallel to the axis of rotation 13 of the piston carrier ring 12.

The output 11 of the motor is arranged in the at least partially open section 5.4 of the piston guide channel 1 and takes place from the piston carrier ring 12.

Fig. 6 and Fig. 7 show a motor with existing on both sides of the piston carrier ring 12 working spaces. 4

The piston channel bottom 3.3 of the piston guide channel 1 has the reverse inclination to the piston carrier ring 12 as the piston guide channel wall section 3.1, so that on both sides of the piston carrier ring 12 "piston guide channels" are formed. The piston carrier ring 12 is movably supported in a longitudinal guide 18 of the piston guide channel wall 3. The piston carrier ring 12 has through transverse slots 19, in each of which a piston 2 is slidably guided, guided by and sealed relative to the two piston guide channel wall sections 3.1, so that

adjacent pistons 2.1, 2.2 each form on both sides of the piston carrier ring 12 working spaces 4, one of which increases in the piston movement through the common piston guide channel 1 and the other is reduced or both are constant.

The Fig. 8 and Fig. 9 shows in a schematic diagram the side view and a section AA of the motor with a guided piston carrier ring 12 for changing the volume the workrooms 4.

The piston guide channel 1 has in the closed piston guide channel section 5.1 to 5.3 two parallel piston guide channel wall sections 3.2, which are interconnected by a final piston guide channel wall section 3.1.

The distance between the piston guide channel wall section 3.1 and the piston guide channel bottom 3.3 is constant. Slight pivoting movements of the pistons 2.1 to 2.n are compensated by the piston support and the piston seal.

In the piston guide channel 1, a piston carrier ring 12 is arranged which, driven by the pistons 2.1 to 2.n, performs a movement in the longitudinal direction of the piston guide channel 1. The piston carrier ring 12 is arranged displaceably relative to the pistons 2.1 to 2.n, so that the change in volume of the working chambers 4 can be achieved by continuously changing distances between the piston carrier ring 12 and the piston guide passage wall section 3.1 closing the respective working space, in which the position of the piston carrier ring 12 in FIG Piston guide channel 1 is changed, the

Piston 2.1 to 2.n in the workspace 4 sealingly abut the piston guide channel wall sections 3.1, 3.2.

The piston carrier ring 12 here consists of mutually coupled plates 17, the at least in the sections 5 with a volume reduction, a constant or slightly magnifying volume and an increasing volume of the working spaces 4 the Piston guide channel 1 in the direction of working spaces 4 sealed share in a piston guide channel 1.1 to form the working spaces 4 and a piston guide channel 1.2, in which the plates 17 penetrate the piston 2.1 to 2.n supported slide or roll.

The plates 17 are movable supported on or in longitudinal guides 18 of the piston guide channel 1, wherein the longitudinal guides 18 are arranged so that the distance to the final piston guide channel wall section 3.1 for the purpose of volume reduction, a constant or slightly magnifying volume and an increasing volume of the work spaces 4 changed.

The guides 18 are arranged in the preferred embodiment outside of the piston guide channel 1.1.

Respective adjacent plates 17 are hinged together.

The output 11 of the motor is arranged in an at least partially open section 5.4 of the piston guide channel 1 and takes place from the piston carrier ring 12.

LIST OF REFERENCE NUMBERS

1

Piston guide channel

2.n

piston

3

Piston channel walls

3.1

final piston guide channel wall section

3.2

parallel piston guide channel wall sections

3.3

Piston guide channel base

4

working space

5

Volume change sections

5.1

Volume reduction section

5.2

Section in constant or slightly increasing volume

5.3

Volume increase section

5.4

Ejecting section

6

piston guide

7

piston guide

8th

piston edge

9

Guide elements in the area of piston corners

10

piston connection

11

output

12

Piston ring carrier

13

Rotation axis of the piston carrier ring

14

Piston guide channel axis

15

shift direction

16

Transverse recesses in the piston carrier ring

17

plates

18

longitudinal guides

19

Transverse slots in the piston carrier ring

Claims (17)

Motor with at least one piston guide channel (1) and in the at least one piston guide channel (1) successively moving piston (2.n), which are driven by a gas expansion,
wherein the piston guide channel (1) is designed to be stationary, annular and at least partially closed by at least one piston guide channel wall (3),
between the adjacent and successively in the at least one piston guide channel (1) moving piston (2.n, 2.n-1) each have a working space (4) is formed by the piston (2.n, 2.n-1) with fixed distance to each other are coupled to each other and in the region of the working spaces (4) with its piston portions on the at least one closed-trained piston guide channel wall (3) sealingly abut,
wherein the volume of the work spaces (4) successively and cyclically when passing through the piston guide channel (1) changed by at least after a section with a continuous volume reduction (5.1) is followed by a section with a constant or slightly magnifying volume (5.2), the Section with a continuous increase in volume (5.3) of the respective working space (4) follows, in which the major part of the gas expansion takes place, and this volume change cycle after a section for expelling (5.4) the expanded gases again connects with a volume reduction. Motor according to claim 1, characterized in that
in the ejection section (5.4), the pistons (2.n) are at least guided. Motor according to one of claims 1 or 2, characterized in that
the portions (5) having a volume reduction, a constant or slightly increasing volume and an increasing volume of the working spaces (4) are arranged in a straight portion of the annular piston guide channel (1), or the at least one annular piston guide channel (1) in its Longitudinal extent is circular. Motor according to one of claims 1 to 3, characterized in that
the piston guide channel (1) circumferentially in the merging sections (5) of the volume change of the working spaces (4) has changed or variable cross-sections, to which the piston guide channel walls (3) sealingly fitting piston sections of the piston (2.n) adapt. Motor according to claim 4, characterized in that
the cross section of the piston guide channel (1) in its largest dimension a square or rhomboid Area is and in the smallest extent a rhomboid slot. Motor according to claim 4 or 5, characterized in that
the cross section of the piston guide channel (1) can be enlarged or reduced by a force effect from the outside. Motor according to one of claims 4 to 6, characterized in that
the pistons (2.n) are collapsible and in the unfolded state have the shape of a square pyramid open on the bottom side with a square or rhomboid bottom cross section and pyramid edges (8) connected in a hinged manner. Motor according to claim 7, characterized in that
the pistons (2.n) at least in the region of a pyramid-bottom corner have a guide element (9) for a guide in the piston guide channel (1). Motor according to claim 1 to 3, characterized in that
in which at least one piston guide channel (1) a piston carrier ring (12) is arranged, which by the piston (2.n) driven movement in Lengthwise of the piston guide channel (1) performs, and the piston (2.n) relative to the piston carrier ring (12) or vice versa slidably disposed, wherein the change in volume of the working spaces (4) by continuously changing distances between the piston carrier ring (12) and a respective working space (4) final, relative to the piston carrier ring (12) located piston guide channel wall portion (3.1) is executable, and wherein the piston ring carrier (12) in the region of the working spaces (4) sealingly against the piston guide channel wall (3). Engine according to claim 9, characterized in that
the at least one piston guide channel (1) comprises at least in the closed piston guide channel section two parallel sections (3.2) of the piston guide channel wall (3) which are connected by the final piston guide channel wall section (3.1). Motor according to claim 9 or 10, characterized in that
the change in distance between the piston carrier ring (12) and the respective working chamber (4) final piston guide channel wall portion (3.1) by an inclination of the piston guide channel wall portion (3.1) to the piston carrier ring (12) and / or by a change in position of the Piston carrier ring (12) in the piston guide channel (1) is made. Motor according to one of claims 9 to 11, characterized in that
the pistons (2.n) are arranged in transverse recesses (16) of the piston carrier ring (12) located on the bottom side in the piston guide channel (1). Motor according to one of claims 9 to 11, characterized in that
the piston channel bottom (3.3) of the at least one piston guide channel (1) the reverse inclination to the piston carrier ring (12) as the piston guide channel wall portion (3.1), so that on both sides of the piston carrier ring (12) piston guide channels (1) are formed, the piston carrier ring (12) in one Longitudinal guide (18) of the two piston guide channels (1) is movably supported and the piston carrier ring (12) has continuous transverse slots (19), in each of which a piston (2.n) displaceable, guided by and sealed against the two piston guide channel wall sections (3.1) is arranged, so that the pistons (2.n, 2.n-1) on both sides of the piston carrier ring (12) form working spaces (4). Motor according to claim 12 or 13, characterized in that
the displacement direction (15) of the piston (2.n) in the piston carrier ring (12) is parallel to the axis of rotation (13) of the piston carrier ring (12). Motor according to one of claims 9 or 11, characterized in that
the piston carrier ring (12) consists of mutually coupled plates (17) which at least in the sections (5) with a volume reduction, a constant or slightly increasing volume and an increasing volume of the working spaces (4) the piston guide channel (1) share sealed in a piston guide channel (1.1) for forming the working spaces (4) and a piston guide channel (1.2), in which the pistons (2.n) penetrating the plates (17) slide or roll supported, the plates (17) resting on or in longitudinal guides (18) of the piston guide channel (1) are movable and the longitudinal guides (18) are arranged so that the distance between the plate to the final piston guide channel wall portion (3.1) for the purpose of volume reduction, a constant or slightly increasing volume and an increasing volume of the working spaces (4) changed. Motor according to claim 13 or 15, characterized in that
the longitudinal guides (18) outside the piston guide channel (1.1) are arranged. Motor according to one of claims 1 to 16, characterized in that
at least one output (11) of the motor in an open or partially open portion of the piston guide channel (1) is arranged, preferably a plurality of power take-offs (11).

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