DE102006062065A1 - Hydrostatic axial piston machine e.g. swash plate machine, has periphery wall with radial elevation formed in longitudinal direction of housing and formed by two periphery wall sections that limit radially extended interior section - Google Patents

Abstract

The machine (1) has a housing (2) for enclosing an interior space (3) with two transverse walls (18a, 18b) and a periphery wall (2c). Swash-plates (4) supported longitudinally adjacent to a cylinder drum (5) are flexibly supported at pistons (9). The plates are adjustably supported back and forth along extending piston bores (6) in the drum. The periphery wall has a radial elevation formed in a longitudinal direction of the housing and formed by two u-shaped periphery wall sections. The sections limit a radially extended interior section.

Description

The The invention relates to an axial piston machine according to the preamble of claim 1 or 6.

A Axial piston machine of this type is generally state of the art, which may be different types, e.g. B. by one so-called swash plate machine or bent axis machine, and wherein each variable to axial piston machines or fixed throughput volume.

In the EP 0 450 623 A1 is z. B. an axial piston machine of the swash plate type with variable flow rate described. From the DE 100 30 147 A1 is z. B. an axial piston machine of the bent axis type with variable or fixed throughput volume.

all Machine types have in common that the round in cross-section cylindrical drum is arranged in a housing interior, the housing peripheral wall surrounds the cylinder block with a sufficient radial distance. For functional operation, the interior is at least partially with the hydraulic medium, in particular hydraulic oil, filled the axial piston machine and that at a low pressure.

Out For reasons of space and material savings one strives the smallest possible cross-sectional size to comply with the housing. That's why it surrounds Peripheral wall of the housing, the cylinder drum with a sufficiently small radial distance. Because the cross-sectional shape of the Cylinder drum is usually round, have common housing one essentially round or hollow cylindrical cross-sectional shape. In axial piston machines variable throughput volume it is known elongated and z. B. arranged axially parallel Adjustment devices in chambers of wall thickening of the housing to arrange, connected by channels with the interior are.

Of the Invention is the object of an axial piston of the initially specified type with respect to a space-saving To improve the shape of their case. In addition, should an at least space hydraulic connection point of the Axial piston machine to a hydraulic circuit and / or to a leak can be achieved. In the further is also a space-favorable Arrangement of parts of an adjusting device for changing aimed at the flow rate of the axial piston machine.

These The object is solved by the features of claim 1 or 6. Advantageous developments of the invention are in the dependent claims described.

Of the Invention is based on the finding that a radial extension the housing of the axial piston machine both inside and on the outside, space-efficient arrangement and / or training possibilities offers.

According to claim 1, the peripheral wall has at least one radial elevation, which elongated in the longitudinal direction of the drive shaft extends, and by two angular or U-shaped peripheral wall sections is formed, which limit a radially expanded interior portion. As a result, on the one hand, a radially expanded interior portion created, the arrangement of additional parts of the axial piston machine is available, for. B. sharing an adjustment to reduce or increase the throughput volume of Axial piston machine, which are adjusting elements for adjusting the throughput volume or stop elements to limit an adjustment can act.

additionally or independently they offer the extended interior section limiting peripheral wall sections in the first ridge of they formed radial elevation an advantageous arrangement point for fasteners for attaching attachments the axial piston machine, for. B. for direct or indirect fastening of connection fittings for hydraulic lines. One Advantage of such an arrangement point is z. B. in that the ridge of the survey with respect to both sides sloping Sidewall sections is sublime and therefore a space-saving or large clearance for mounting or dismounting the respective attachment is present.

For an attachment in the form of a line connection part results in the Advantage that the radially expanded interior section fluidly from Advantage is because a larger free interior is present in the region of the flow opening.

In the axial piston machine according to the invention according to claim 6, a radial elevation with an angular or U-shaped cross-section is arranged on the circumference of the transverse wall of the housing, in whose ridge region a hydraulic connection point is arranged with a connection opening. As already described above developments of the invention, this alternative of the invention leads to a raised and thus from the surrounding area of the housing transversely spaced hydraulic connection point, which not only a spatially favorable arrangement but also a handha due to the surrounding space easy to assemble and disassemble the associated hydraulic line guaranteed. This embodiment of the invention also makes it possible not only to arrange the hydraulic line radially, but also angled or angularly curved form, z. B. at an acute angle of z. B. angled about 45 °.

in the Under the invention, a plurality of elevations transversely to each other opposite and / or on one side of the housing and / or in the circumferential direction, whereby an angular or semicircular or substantially quadrangular cross-sectional shape for the housing results and correspondingly more radially expanded interior sections present are.

If two, three or four according to the invention Elevations arranged offset in the circumferential direction, let an adjusting device for adjusting and adjusting the Throughput volume of the axial piston machine and a limiting device the maximum setting, z. B. the swivel limitation of a swash plate, realize in a space-saving manner.

advantageous Further developments of the invention lead to further improvements the space-favorable design of the housing and / or Attachable attachments and improvements in the attachment the axial piston machine on a support, wherein the Assembly or disassembly of existing in the housing interior Components of the axial piston machine is improved.

following Advantageous embodiments of the invention with reference to a preferred embodiment and the drawing explained in more detail. Show it:

1 an axial piston machine according to the invention in a schematic representation in axial section;

2 a swash plate of the axial piston machine in its position minimum throughput volume in perspective detail view;

3 an axial piston machine according to the invention in a perspective front view and

4 a rear pot housing of the axial piston after 1 or 3 in the front view.

In the 1 illustrated, exemplary trained and in its entirety with 1 designated axial piston machine has a housing 2 in, in its interior 3 a swash plate 4 and a cylinder drum 5 are arranged axially side by side. In the cylinder drum 5 with round cross-sectional shape are distributed on a circumference piston holes 6 arranged, the z. B. parallel to the central axis 7 of the cylinder block 5 and the axial piston machine 1 extend and at the swash plate 4 open side facing open. In the piston holes 6 are preferably cylindrical pistons in cross section 9 mounted longitudinally displaceable, with their piston heads working chambers 11 in the piston holes 6 in the direction of the swashplate 4 limit. The swash plate 4 facing the foot ends of the pistons 9 are each through a joint 12 on the facing inclined surface 4a the swash plate 4 supported, with sliding shoes 13 may be present, between which and the foot ends, preferably as ball joints with a ball head and a ball recess formed joints 12 are arranged.

The cylinder drum 5 lies with her the swash plate 4 remote end face on a control disk 14 on, at the at least two control openings 15a and 15b are arranged diametrically opposite one another, the longitudinal sections of an indicated supply line 16 and a discharge line 17 form, extending through an adjacent housing transverse wall 18a extend to the the control disk 14 is held. The cylinder drum 5 is on a shoot shaft 19 arranged, which are rotatable in the housing 2 is stored and its axis of rotation 21 coaxial to the central axis 7 the cylinder drum 5 runs.

In the present embodiment, the housing 2 from a cup-shaped housing part 2a with a caseback 2 B and a peripheral wall 2c and a lid-shaped flange 2d formed at the free edge of the peripheral wall 2c is present, the thus by a screwing 22 with hinted screws 22a is bolted and the one front bulkhead 18b of the housing forms.

The shoot shaft 19 holding the cylinder drum 5 in a camp hole 5a rotatably enforced, is by means of suitable bearings 25 . 25a at the bottom of the case 2 B and the front bulkhead 18b or on the flange 2d rotatably mounted, where they are the transverse wall 18b or the flange 2d in a through hole 23 axially interspersed, therein by a ring seal 24 is sealed and with a pinion 19a from the case 2 protrudes axially. The cup-shaped housing part 2a and the flange 2d lie with flat contact surfaces 2f to each other, creating a Teilungsfuge 26 is formed between these components, which is sealed in a manner not shown, for. B. by a ring seal. For coaxial positioning of the flange 2d and the cup-shaped housing 2a one another is preferably a centering 27 provided, z. B. in the form of one of the associated system area 2f protruding projection, which fits into a matching recess in the opposite contact surface 2f or in the inner edge of the interior 3 fits.

In the swash plate 4 is a through hole 28 , z. B. coaxial, arranged by the drive shaft 19 is traversed with radial movement play. The swash plate 4 is inside the flange 2d axially forward, ie to the drive pin 19a towards, and radially supported, preferably positively supported.

In the axial piston machine 1 it can be one with a constant or variable throughput volume. In the latter case, it has an in 1 by a double arrow clarified adjusting device 31 on, with the throughput volume is selectively reduced or increased, with different known constructions can be used.

In the present embodiment, the swash plate 4 in a swivel joint 32 about a transverse to the axis of rotation 21 or longitudinal center axis directed pivot axis 32a by an adjustment mechanism 31a adjustable in one or the other direction of pivoting and lockable in the respective adjustment position.

The swivel joint 32 may be formed by a so-called pivoting cradle, with a transversely continuous or two on both sides of the drive shaft 19 arranged circular arc section-shaped concave joint surfaces 32b on the inside of the flange 2d and a transversal or two on either side of the feedthrough hole 28 arranged circular arc section-shaped convex articular surfaces 32c on the swash plate 4 , In the embodiment, the pivot joint 32 a plain bearing. But it can also be formed by a rolling bearing or needle roller bearings, which is located between the articular surfaces 32b . 32c arranged rolling elements can be realized in a small design.

The peripheral wall 2c of the housing 2 has a radial and in cross-section angular or U-shaped or roof-shaped elevation 34a on, whose ridge 34d in the longitudinal direction of the tubular peripheral wall 2c extends. The assessment 34a is by two angularly or U-shaped peripheral wall sections 2e formed, which rise tangentially or sekantial with respect to a conceivable hollow cylindrical peripheral wall and in the ridge 34d the survey 34a connected to each other. In the embodiment, the survey extends 34a over the axial length L1 of the peripheral wall 2c or as a survey 34b about the thickness L2 of the rear bulkhead 18a of the pot housing 2a , where the flange 2d preferably also a corresponding survey 34c can show that with the survey 34a may be approximately congruent in the axial projection and about the thickness L3 of the front transverse wall 18b can extend. It can thus be over the entire length L of the housing 2 extending survey 34 be given, the axially through the respective integrally formed elevations 34a . 34b . 34c is composed, with the surveys 34a . 34b are also connected in one piece with each other axially.

Because the survey 34b on the circumference of the rear bulkhead 18a or the housing bottom 2 B not the interior 3 of the housing 2 limited, in this embodiment, no interior extension exists. In this embodiment of the invention, the survey 34b through lateral surface sections 34e limited, the angle or U-shaped are arranged and the survey 34b between them. This also applies to the survey 34c on the circumference of the flange 2d ,

The assessment 34a limited with its peripheral wall sections 2e with z. B. substantially the same thickness d a radially expanded interior portion 36 , which is the protected arrangement of optional and yet to be described detail constructions or components of the axial piston machine 1 space suitable.

The peripheral wall 2c can two surveys arranged transversely opposite one another 34a or more, e.g. B. three or four, in the circumferential direction, z. B. arranged at about 90 °, elevations arranged offset 34a exhibit. In the presence of four circumferentially spaced elevations 34a can the peripheral wall 2c have a substantially quadrangular or rectangular cross-sectional shape, wherein the corners may be rounded in the sense of round corners and the side walls extending therebetween 2g - Seen in cross-section - may be slightly curved to the outside, as it 3 and 4 demonstrate. The side walls can 2g in each case through the two peripheral wall sections facing away from one another 2e from both circumferentially adjacent elevations 34a be formed.

Preferably, those are also between the surveys 34b . 34c extending peripheral sections 34e of the case bottom 2 B and the flange 2d to the shape and size of the sidewall sections 2g the peripheral wall 2c customized.

It can, for. B. one of the adjustment 31 associated adjusting mechanism 31a in an interior section 36 be arranged, with respect to the cylinder drum 5 space-wise outward or along the pivot axis 33 and so be offset at an angle or diagonally.

To the mechanical connection of the adjustment mechanism 31a with the swash plate 4 to improve, this also has at least one radial elevation 37 on, the associated interior section 36 axially opposite, so that in 2 as against the survey 37 Directional arrow or as a double arrow clarified adjustment mechanism 31a at the survey 37 attack in the sense of pressure and / or train practice.

Preferably also on the swash plate 4 every interior section 36 axially opposite a survey 37 arranged, with the presence of four surveys 37 the swash plate 4 may have a quadrangular or rectangular shape and the corners of the swash plate 4 can also be rounded.

The adjusting device 31 can two axially counteracting adjustment mechanisms 31a1 . 31a2 have, on both sides of the pivot axis 33 can be arranged at a radial distance and thereby with respect to the pivot axis 33 can be arranged transversely or obliquely opposite each other. The latter can be done 2 remove. Such mutually opposing effective adjustment mechanisms 31a1 . 31a2 can z. B. be formed by a hydraulic Ausschwenkkolben and a hydraulic rear pivot piston, the axially opposite or in the same direction on the swash plate 4 can be effective, in the latter case, one of the two pistons overprinted the other piston.

In at least one radially expanded interior section 36 can be roomy also a swivel limiting device 41 each for limiting the maximum and / or minimum pivot angle of the swash plate 4 Arrange. 2 and 4 show two Schwenkbegrenzungsvorrichtungen 41 of which one is intended for the maximum and the other for the minimum pivot angle position. The at least one pivot limiting device 41 can z. B. by a stop screw 41a be formed in a thread of an inner neck of the peripheral wall, not shown 2c is screwed in and with respect to the pivot axis 33 transverse or obliquely directed distance against the swash plate 4 or the associated survey 37 optionally screwed back and forth, z. B. by means of an attacking on the head of the stop screw screwdriver.

To the accessibility to the at least one adjustable pivot limiting device 41 or stop screw 41a to improve, this or a receiving hole or threaded hole in the peripheral wall 2c preferably extend obliquely outwards, so that the pivot limiting device 41 or the screw head is accessible from the outside. This is exemplary in 3 dargstellt, in the top right arranged pivot limiting device 41 a stop screw 41a has, which extends obliquely upwards and backwards in a correspondingly obliquely arranged hole or threaded hole to the outside and is thus accessible from the outside. Accordingly, the other swing limiting device 41 or stop screw 41a be arranged accessible from the outside. So it can at least one survey 34a . 34b . 34c and the or at least one adjusting mechanism 31a or Schwenkbegrenzungsvorokrrichtung 41 - Seen axially - between the pivot axis 33 containing longitudinal plane E1 and a perpendicular to this longitudinal center plane E2 be arranged.

Also, the one or both Schwenkbegrenzungsvorrichtungen 41 can thus on both sides of the pivot axis 33 be arranged transversely or obliquely opposite with respect to this. The in 1 not shown another swivel limiting device 41 be formed accessible from the outside, as it is for the top right arranged pivot limiting device 41 has been described, for. B. be arranged in a mirror image with respect to the longitudinal plane E1 and the longitudinal plane E2.

The at least one survey 34a . 34b is also space favorable for the arrangement of hydraulic functional elements, such. B. at least one connection point 38 with a connection opening for the supply or discharge or flushing of the hydraulic medium, in particular hydraulic oil. In the area of the connection opening 38a1 . 38a2 are also fasteners 39a provided, the parts of a fastening device 39 for attaching connection fittings or connecting lines, z. B. the supply or discharge line 16 . 17 , or a leakage line.

In the embodiments, one or are two connection openings 38a1 . 38a2 in the first 34d the survey 34a and or 34b arranged in the longitudinal region L2, in which the rear transverse wall 18a or the housing bottom 2 B located and / or in the longitudinal region L1 of the peripheral wall 2c , The connection opening 38a1 respectively. 38a2 is through a the peripheral wall 2c or the caseback 2 B in the first 34d formed transversely passing hole, wherein the central axis 38b the connection opening 38a1 . 38a2 or the hole in the bisector of the peripheral wall sections 2e or lateral surface sections 34e is located or a z. B. obtuse angle W1 of about 135 ° or at the entrance At an approximately 45 ° fitting, it includes an acute angle W2 of about 45 °.

In the invention, this can be the connection opening 38a1 forming hole according to 3 left directly serve as a fastener for an associated hydraulic line, z. B. in the sense of a threaded connection, so that the hole itself a fastener 39a the fastening device 39 is.

The embodiment in 3 right shows as fasteners 39a one approximately perpendicular to the central axis 38b extending and the connection opening 38a2 surrounding acreage 39b and two or more mounting holes opposing each other 39c , preferably in the cultivated area 39b , which are used to screw a connection fitting for a hydraulic line to the mounting surface 39b attachable and not shown by screws to the peripheral wall 2c can be screwed.

The acreage 39b and / or the connection opening 38a1 is preferably located on or in a second survey 42 that is in the sense of an approach from the first survey 34a . 34b rises.

A second connection opening 38a1 or 38a2 may be in the range of one of the other circumferentially offset surveys 34a . 34b be arranged, for. B. in the diametrically opposite survey 34a . 34b , like it 4 shows. It can this connection opening 38a1 . 38a2 same or different fasteners 39a a fastening device 39 for securing an associated hydraulic line, eg. B. of the existing circuit, be assigned.

As can be seen in particular 4 can detect, at the junction 38 top right connection fitting 38c a connection element 38d have for an associated line whose central axis 38e parallel to the contact surface 39b or parallel to the abutting contact surface of the connection fitting 38c extends and with the central axis 38b includes an approximately right angle. In such an arrangement, the central axis closes 38e the connection fitting 38c with the adjacent sidewall portion 2g the acute angle W2 of about 45 °.

In the context of the invention, however, the connection fitting 38c in one piece with the survey 34a . 34b be connected.

It is thus independent of the above-described embodiment of the connection points 38 for the hydraulic circuit also advantageous only in the at least one survey 34a a connection point 38 to arrange for a leakage line, said connection point in the longitudinal region L1 of the interior 3 is arranged.

The peripheral wall sections 2e the peripheral wall 2c Also lead to a broadening and improvement of a plant on the side wall sections forming it, especially if at least one survey concerned 34a and or 34b not rounded but angular is designed as it 3 above and 4 show top left. Such a peripheral wall section 2e is particularly suitable when its outer surface is flat, as a growing area 45 for a control device 46 for driving in the associated interior section 36 arranged adjusting mechanism 31a , The drive unit 46 has connections for electrical and / or hydraulic supply.

The flange 2d is through a screw connection 51 with several distributed on the circumference arranged screws 51a with the pot housing 2a detachably connected, the through-holes in the flange 2d pass through and threaded holes in the edge region of the peripheral wall 2c are screwed in.

For fastening the axial piston machine 1 on a carrier, not shown, for. B. a machine frame, is a second indicated screw 52 provided, which distributes several on the circumference, z. B. in the surveys 34c , arranged screw holes 52a in the flange 2d have, for screws, not shown, which are insertable therein and threaded into threaded holes, not shown, of the carrier can be screwed. The screw holes 52a may be formed by circumferentially open slots.

The flange 2d Can also be used as an adapter for adapting the axial piston machine 1 to different carriers (eg from different manufacturers). For such a case are two flanges 2d provided, the screw holes 51a for a same hole pattern of a same screw connection 51 are equally formed while the two flanges 2d screw holes 52a have different hole patterns, which are each adapted to the associated hole pattern of the respective carrier.

The Invention is not on the described embodiment limited and is suitable for. B. also for axial piston machines in bent-axis design. All described and / or drawn Features may in the context of the invention with each other be combined.

QUOTES INCLUDE IN THE DESCRIPTION

This list The documents listed by the applicant have been automated generated and is solely for better information recorded by the reader. The list is not part of the German Patent or utility model application. The DPMA takes over no liability for any errors or omissions.

Cited patent literature

• - EP 0450623 A1 [0003]
• - DE 10030147 A1 [0003]

Claims (16)

Hydrostatic axial piston machine ( 1 ), with - a housing ( 2 ), with two transverse walls ( 18a . 18b ) and one of these longitudinally interconnecting peripheral wall ( 2c ) an interior ( 3 ), - a drive shaft ( 19 ), which are longitudinally in the housing ( 2 ) and rotatable in the housing ( 2 ), and - one alongside the cylindrical drum ( 5 ) in the housing ( 2 ) mounted swash plate ( 4 ), on the piston ( 9 ) are hingedly supported, which in approximately longitudinally extending piston holes ( 6 ) in the cylinder drum ( 5 ) are mounted displaceable back and forth, characterized in that the peripheral wall ( 2c ) at least one radial elevation ( 34a ), which in the longitudinal direction of the housing ( 2 ) is elongated, and by two angular or U-shaped peripheral wall sections ( 2e ) is formed, which has a radially enlarged interior portion ( 36 ) limit. Hydrostatic axial piston machine according to claim 1, characterized in that the elevation ( 34a ) over the length (L1) of the interior ( 3 ). Hydrostatic axial piston machine according to claim 1 or 2, characterized in that two elevations ( 34a ) are arranged opposite to each other or more, z. B. three or four, surveys ( 34a ) are offset in the circumferential direction to each other. Hydrostatic axial piston machine according to one of the preceding claims, characterized in that the cylinder drum ( 5 ) with its swash plate ( 4 ) facing away from the inside at one between her and a transverse wall ( 18a ) arranged control disc ( 14 ), and the at least one survey ( 34a ) also along the transverse wall ( 18a ) or over both transverse walls ( 18a . 18b ). Hydrostatic axial piston machine according to one of the preceding claims, characterized in that in the first ( 34d ) of the survey ( 34a ; 34b ) a hydraulic connection point ( 38 ) with a connection opening ( 38a1 ; 38a2 ) is arranged or are. Hydrostatic axial piston machine ( 1 ), with - a housing ( 2 ), with two transverse walls ( 18a . 18b ) and one of these longitudinally interconnecting peripheral wall ( 2c ) an interior ( 3 ), - a drive shaft ( 19 ), which are longitudinally in the housing ( 2 ) and rotatable in the housing ( 2 ), and - one alongside the cylindrical drum ( 5 ) in the housing ( 2 ) mounted swash plate ( 4 ), on the piston ( 9 ) are hingedly supported, which in approximately longitudinally extending piston holes ( 6 ) in the cylinder drum ( 5 ) are slidably mounted back and forth, wherein the cylinder drum ( 5 ) with its swash plate ( 4 ) on one side between it and a transverse wall ( 18a ) arranged control disc ( 14 ) is applied, characterized in that on the circumference of this transverse wall ( 18a ) a radial elevation ( 34b ) is arranged with an angular or U-shaped cross-section, in whose ridge area a hydraulic connection point ( 38 ) with a connection opening ( 38a1 ; 38a2 ) is arranged. Axial piston machine according to claim 6, characterized in that the elevation ( 34b ) at least partially along also on the peripheral wall ( 2c ) or on the other transverse wall ( 18b ). Hydrostatic axial piston machine according to one of the preceding claims 5 to 7, characterized in that at the hydraulic connection point ( 38 ) Fasteners ( 39a ) are arranged, the parts of a fastening device ( 39 ) are for attaching a hydraulic line or a connection fitting. Hydrostatic axial piston machine according to claim 8, characterized in that at the connection point ( 38 ) at least one, preferably flat, contact surface ( 39b ) is provided. Hydrostatic axial piston machine according to claim 8 or 9, characterized in that the fastening elements ( 39a ) at a second survey ( 42 ), which differ from the first survey ( 34a . 34b ), z. B. only in the area of the connection point ( 38 ) raises. Hydrostatic axial piston machine according to one of the preceding claims, characterized in that the throughput volume of the axial piston machine ( 1 ) by an adjusting device ( 31 ) with an adjusting mechanism ( 31a ) is optionally enlargeable or reducible, and preferably the swash plate ( 4 ) as part of the adjusting device ( 31 ) in a swivel joint ( 32 ) about a directed pivot axis ( 32a ) is pivotally mounted. Hydrostatic axial piston machine according to claim 11, characterized in that the adjusting mechanism ( 31a ) and / or a swivel-limiting device ( 41 ) is elongated or are and in the longitudinal direction of the axial piston machine ( 1 ) in the or one of the extended ones Interior sections ( 36 ) with respect to the pivot axis ( 33 ) extends transversely offset or extend. Hydrostatic axial piston machine according to one of the preceding claims, characterized in that one or two transversely spaced from each other having elevations ( 34a . 34b . 34c ) with respect to the pivot axis ( 33 ) are arranged transversely offset. Hydrostatic axial piston machine according to claim 12 or 13, characterized in that on both sides of the pivot axis ( 33 ) two transversely spaced radial elevations ( 34a ) with extended interior sections ( 36 ) are arranged and preferably on each side of the pivot axis ( 33 ) an adjusting mechanism ( 31a ) and a swivel limiting device ( 41 ) are arranged, in particular, are arranged obliquely opposite one another. Hydrostatic axial piston machine according to claim 4, characterized in that the transverse wall ( 18a ) through the bottom wall ( 2 B ) of a pot housing ( 2a ) is formed. Hydrostatic axial piston machine according to one of the preceding claims, characterized in that the housing ( 2 ) at least in the area of the at least one survey ( 34a . 34b . 34c ) one through four side wall sections ( 2f ) has limited cross-sectional shape, in particular a four- or rectangular cross-sectional shape, preferably with rounded corners.