AXIAL PISTON ENGINE HAVING A HOUSING WITH A RADIALLY WIDENED INTERIOR PORTION

Abstract

The invention relates to a hydrostatic axial piston engine (1), having a housing (2), which with two transverse walls (18a, 18b) and a peripheral wall (2c) connecting these longitudinally to one another surrounds an interior (3), a driving shaft (19), which extends longitudinally in the housing (2) and is mounted rotatably in the housing (2), and a swash plate (4), which is mounted longitudinally adjacent to the cylinder drum (5) in the housing (2) and supported against which in an articulated manner are pistons (9) that are reciprocably mounted in approximately longitudinally extending piston holes (6) in the cylinder drum (5). In order to improve the axial piston engine (1) in terms of a spatially advantageous shape, the peripheral wall (2c) has at least one radial elevation (34a), which is constructed in an elongate manner in the longitudinal direction of the housing (2) and which is formed by two peripheral wall portions (2e), which are arranged in an angular or U-shaped manner and delimit a radially widened interior portion (36).

Description

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

An axial piston engine of this type is general prior art and may be of different types, such as for example a so-called swash plate engine or inclined axis engine, wherein these may be in each case axial piston engines of variable or fixed throughput volume.

In EP 0 450 623 A1 for example a swash-plate-type axial piston engine with a variable throughput volume is described. DE 100 30 147 A1 discloses for example an inclined-axis-type axial piston engine with a variable or fixed throughput volume.

What all engine types have in common is that the, in cross section, round cylinder drum is disposed in a housing interior, the housing peripheral wall of which surrounds the cylinder block with an adequate radial clearance. For functional operation, the interior is filled at least partially with the hydraulic medium, in particular hydraulic oil, of the axial piston engine, namely at a low-pressure.

In an attempt to save space and material, as low a cross-sectional size as possible is to be observed for the housing. For this reason, the peripheral wall of the housing surrounds the cylinder drum with a sufficiently low radial clearance. Since as a rule the cross-sectional shape of the cylinder drum is circular, conventional housings have a substantially circular and/or hollow-cylindrical cross-sectional shape. In axial piston engines of variable throughput volume, it is known to dispose elongate and for example paraxially arranged adjusting devices in chambers of wall thickenings of the housing, which are connected by channels to the interior.

The underlying object of the invention is to improve an axial piston engine of the initially indicated type in terms of a spatially advantageous shape of its housing. Furthermore, an at least spatially advantageous hydraulic connection point of the axial piston engine to a hydraulic circuit and/or to a leakage port is to be achieved. A further object is to realize a spatially advantageous arrangement of parts of an adjusting device for varying the throughput volume of the axial piston engine.

This object is achieved by the features of claim 1 or 6. Advantageous developments of the invention are described in the sub-claims.

The invention is based on the discovery that a radial widening of the housing of the axial piston engine offers spatially advantageous arrangement- and/or design options both internally and externally.

According to claim 1 the peripheral wall has at least one radial elevation, which extends in an elongate manner in the longitudinal direction of the driving shaft and which is formed by two peripheral wall portions, which are disposed in an angular or U-shaped manner and delimit a radially widened interior portion. On the one hand, this creates a radially widened interior portion that is available for the disposition of additional parts of the axial piston engine, for example parts of an adjusting device for decreasing or increasing the throughput volume of the axial piston engine, wherein these parts may be adjusting elements for adjusting the throughput volume or stop elements for limiting an adjusting movement.

In addition or independently thereof, the peripheral wall portions that delimit the widened interior portion offer, in the region of the apex of the radial elevation they form, an advantageous arrangement place for fastening elements for fastening attachments of the axial piston engine, for example for the direct or indirect fastening of connection fittings for hydraulic lines. One advantage of such an arrangement place is for example that the apex of the elevation is elevated in relation to the downward sloping side wall portions on either side and for this reason there is a spatially advantageous and/or large free space for assembling and/or disassembling the respective attachment.

For an attachment in the form of a line connection part the advantage arises that the radially widened interior portion is fluidically advantageous because there is a larger free interior in the region of the flow opening.

In the axial piston engine according to the invention in accordance with claim 6, on the periphery of the transverse wall of the housing a radial elevation of an angular or U-shaped cross section is disposed, in the apex region of which a hydraulic connection point with a connection opening is disposed. Like the previously described developments of the invention, this alternative according to the invention also leads to a hydraulic connection point, which is elevated and hence spaced transversely apart from the surrounding region of the housing and which because of the clearance surrounding it guarantees not only a spatially more advantageous arrangement but also handling-friendly assembly and/or disassembly of the associated hydraulic line. This development according to the invention also makes it possible for the hydraulic line not only to be disposed radially but also to be of an angular design or bent into an angular shape, for example at an acute angle of for example ca. 45°.

Within the scope of the invention, a plurality of elevations may be disposed diagonally opposite one another and/or on one side of the housing and/or offset in the peripheral direction, thereby resulting in a polygonal or semicircular or substantially square cross-sectional shape for the housing as well as the existence of a corresponding number of radially widened interior portions.

If in each case two, three or four elevations according to the invention are disposed offset in the peripheral direction, an adjusting device for adjusting and setting the throughput volume of the axial piston engine and a device for limiting the maximum setting, for example for limiting the swivel of a swash plate, may be realized in a spatially advantageous manner.

Advantageous developments of the invention lead to further improvements of the spatially advantageous design of the housing and/or attachments attachable thereto and to improvements in the fastening of the axial piston engine to a carrier, wherein the assembly and/or disassembly of the components of the axial piston engine that are situated in the housing interior is also improved.

There now follows a detailed description of advantageous developments of the invention with reference to a preferred embodiment and the drawings. The drawings show:

FIG. 1 a diagrammatically represented axial section of an axial piston engine according to the invention;

FIG. 2 a perspective single-part representation of a swash plate of the axial piston engine in its minimum throughput volume position;

FIG. 3 a perspective front view of an axial piston engine according to the invention and

FIG. 4 a front view of a rear pot-type housing of the axial piston engine according to FIG. 1 or 3.

The axial piston engine of an exemplary construction that is represented in FIG. 1 and denoted as a whole by 1 comprises a housing 2, in the interior 3 of which a swash plate 4 and a cylinder drum 5 are disposed axially adjacent to one another. Disposed in the cylinder drum 5 of a circular cross-sectional shape and distributed along a periphery are piston holes 6, which extend for example parallel to the centre line 7 of the cylinder block 5 and the axial piston engine 1 and open out at the side facing the swash plate 4. In the piston holes 6 pistons 9, which are preferably cylindrical in cross section, are mounted in a longitudinally displaceable manner and with their piston heads delimit working chambers 11 in the piston holes 6 in the direction of the swash plate 4. The bottom ends of the pistons 9 facing the swash plate 4 are supported in each case by means of a joint 12 on the opposing oblique face 4a of the swash plate 4, wherein sliding blocks 13 may be provided, between which and the bottom ends are disposed the joints 12, which preferably take the form of ball joints having a ball head and a ball socket.

The end of the cylinder drum 5 remote from the swash plate 4 rests against a cam disc 14, on which at least two control openings 15a and 15b are disposed diametrically opposite one another and form longitudinal portions of an indicated supply line 16 and a discharge line 17, which extend through an adjacent housing transverse wall 18a, against which the cam disc 14 is held. The cylinder drum 5 is disposed on a driving shaft 19, which is mounted rotatably in the housing 2 and the axis of rotation 21 of which extends coaxially with the centre line 7 of the cylinder drum 5.

In the present embodiment, the housing 2 is formed by a pot-shaped housing part 2a having a housing base 2b and a peripheral wall 2c as well as by a lid-shaped flange 2d, which lies against the free edge of the peripheral wall 2c, is connected thereto by a screw connection 22 using screws 22a, traces of which are represented, and forms a front transverse wall 18b of the housing.

The driving shaft 19, which penetrates the cylinder drum 5 in a rotatably fixed manner in a bearing hole 5a, is rotatably mounted by means of suitable bearings 25, 25a on the housing base 2b and the front transverse wall 18b and/or on the flange 2d, wherein the driving shaft 19 axially penetrates the transverse wall 18d and/or the flange 2d in a through-hole 23, is sealed therein by means of a ring seal 24 and with a driving pin 19a projects axially from the housing 2. The pot-shaped housing part 2a and the flange 2d are in mutual abutment with flat seating faces 2f, thereby forming a parting joint 26 between these components that is sealed in a non-illustrated manner, for example by means of a ring seal. For coaxially positioning the flange 2d and the pot-shaped housing 2a on one another a centring device 27 is preferably provided, for example in the form of a projection that protrudes from the associated seating face 2f and fits into a matching recess in the opposite seating face 2f or into the inner edge of the interior 3.

Disposed, for example coaxially, in the swash plate 4 is a through-hole 28, which is penetrated by the driving shaft 19 with radial motional clearance. The swash plate 4 is supported axially in a forward direction, i.e. in the direction of the driving pin 19a, and radially against the inside of the flange 2d, preferably in a positive manner.

The axial piston engine 1 may be an axial piston engine with a fixed or variable throughput volume. In the latter case, it has an adjusting device 31, which is indicated in FIG. 1 by a double arrow and by means of which the throughput volume may be either decreased or increased, wherein different known designs may be used.

In the present embodiment, by means of an adjusting mechanism 31a the swash plate 4 is adjustable in a swivel joint 32 in one or the other swivelling direction about a swivelling axis 32a oriented transversely of the axis of rotation 21 and/or longitudinal centre line and is lockable in the respective adjusted position.

The swivel joint 32 may be formed by a so-called swivelling cradle, comprising either one transversely continuous or two arc-segment-shaped concave joint faces 32b disposed on both sides of the driving shaft 19 on the inside of the flange 2d and either one transversely continuous or two arc-segment-shaped convex joint faces 32c disposed on both sides of the through-hole 28 on the swash plate 4. In the embodiment, the swivel joint 32 is a slide bearing. It may however be formed also by a rolling-contact bearing or needle bearing, which may be realized in a small-scale design by rolling bodies disposed between the joint faces 32b, 32c.

The peripheral wall 2c of the housing 2 has a radial elevation 34a, which is angular or U-shaped and/or roof-shaped in cross section and the apex 34d of which extends in the longitudinal direction of the tubular peripheral wall 2c. The elevation 34a is formed by two peripheral wall portions 2e disposed in an angular and/or U-shaped manner, which are elevated tangentially or like a secant in relation to an imaginary hollow-cylindrical peripheral wall and are connected to one another in the apex 34d of the elevation 34a. In the embodiment, the elevation 34a extends over the axial length L1 of the peripheral wall 2c or also as elevation 34b over the thickness L2 of the rear transverse wall 18a of the pot-type housing 2a, wherein the flange 2d may preferably also have a corresponding elevation 34c, which in the axial projection may be approximately congruent with the elevation 34a and may extend over the thickness L3 of the front transverse wall 18b. It is therefore possible to define an elevation 34 that extends over the entire length L of the housing 2 and is composed axially of the in each case integrally formed elevations 34a, 34b, 34c, wherein the elevations 34a, 34b are also axially integrally connected to one another.

As the elevation 34b at the periphery of the rear transverse wall 18a and/or of the housing base 2b does not delimit the interior 3 of the housing 2, in this development there is no interior widening either. In this development according to the invention, the elevation 34b is delimited by lateral surface portions 34e, which are disposed in an angular or U-shaped manner and between them include the elevation 34b. This applies also to the elevation 34c at the periphery of the flange 2d.

The elevation 34a with its peripheral wall portions 2e of for example substantially equal thickness d delimits a radially widened interior portion 36, which is suitable for the protected arrangement of selective, yet to be described detail designs or components of the axial piston engine 1 in a spatially advantageous manner.

The peripheral wall 2c may comprise two elevations 34a disposed diagonally opposite one another or a plurality of elevations 34a, for example three or four, disposed offset in the peripheral direction, for example by approximately 90°. Given the existence of four elevations 34a arranged distributed along the periphery, the peripheral wall 2c may have a substantially square or rectangular cross-sectional shape, wherein the corners may be rounded in the sense of rounded corners and the side walls 2g extending therebetween—viewed in cross section—may be curved slightly in an outward direction, as shown in FIGS. 3 and 4. In this case, the side walls 2g may be formed in each case by the two mutually remote peripheral wall portions 2e of both elevations 34a that are adjacent to one another in peripheral direction.

Preferably, the peripheral wall portions 34e of the housing base 2b and the flange 2d that extend between the elevations 34b, 34c are also adapted to the shape and size of the side wall portions 2g of the peripheral wall 2c.

It is possible for example for an adjusting mechanism 31a forming part of the adjusting device 31 to be disposed in an interior portion 36, and namely be offset in a spatially advantageous manner outwards or alternatively along the swivelling axis 33 and hence obliquely and/or diagonally in relation to the cylinder drum 5.

In order to improve the mechanical connection of the adjusting mechanism 31a to the swash plate 4, the swash plate 4 also has at least one radial elevation 37 that lies axially opposite the associated interior portion 36, so that the adjusting mechanism 31a, which is indicated in FIG. 2 as an arrow pointing towards the elevation 37 or as a double arrow, may act in the sense of an exertion of pressure and/or tension on the elevation 37.

Preferably, on the swash plate 4 too there is an elevation 37 disposed axially opposite each interior portion 36, wherein given the existence of four elevations 37 the swash plate 4 may have a square or rectangular shape and the corners of the swash plate 4 may also be rounded.

The adjusting device 31 may comprise two adjusting mechanisms 31a1, 31a2, which act axially in opposite directions and which may be disposed with a radial spacing on both sides of the swivelling axis 33 and in this case may be disposed in relation to the swivelling axis 33 diagonally or obliquely opposite one another. This last detail may be seen in FIG. 2. Such adjusting mechanisms 31a1, 31a2 acting in opposite directions to one another may be formed for example by means of a hydraulic swing-out piston and a hydraulic swing-back piston, which may act axially in opposite directions or in the same direction upon the swash plate 4, wherein in the latter case one of the two pistons actuates the other piston.

In at least one radially widened interior portion 36 a swivel-limiting device 41 in each case for limiting the maximum and/or minimum swivel angle of the swash plate 4 may also be disposed in a spatially advantageous manner. FIGS. 2 and 4 show two swivel-limiting devices 41, of which one is provided for the maximum and the other for the minimum swivel angle position. The at least one swivel-limiting device 41 may be formed for example by means of a stop screw 41a, which is screwed into a thread of a non-illustrated inner projection of the peripheral wall 2c and with a spacing oriented transversely or obliquely in relation to the swivelling axis 33 may be screwed selectively to and fro relative to the swash plate 4 and/or the associated elevation 37, for example by means of a screwdriver applied to the head of the stop screw.

In order to improve the access to the at least one adjustable swivel-limiting device 41 or stop screw 41a, it and/or a hole or threaded hole receiving it may extend in the peripheral wall 2c preferably obliquely outwards so that the swivel-limiting device 41 and/or the screw head is accessible from outside. This is represented by way of example in FIG. 3, in which the swivel-limiting device 41 disposed top right comprises a stop screw 41a, which extends outwards in an obliquely upward and backward direction in a correspondingly obliquely disposed hole or threaded hole and is therefore accessible from outside. In a corresponding manner the other swivel-limiting device 41 and/or stop screw 41a may also be disposed so as to be accessible from outside. Thus, the at least one elevation 34a, 34b, 34c and the at least one adjusting mechanism 31a and/or swivel-limiting device 41 may be disposed—viewed axially—between the longitudinal plane E1 containing the swivelling axis 33 and a longitudinal centre plane E2 situated at right angles thereto.

The one or two swivel-limiting devices 41 may therefore also be disposed on both sides of the swivelling axis 33 diagonally or obliquely opposite one another in relation thereto. In this case, the other swivel-limiting device 41 that is not represented in FIG. 1 may be designed so as to be accessible from outside, in the manner described for the swivel-limiting device 41 disposed top right, and may be disposed for example in an, in relation to the longitudinal plane E1 and/or the longitudinal plane E2, mirror-image position.

The at least one elevation 34a, 34b is suitable also in a spatially advantageous manner for the arrangement of hydraulic functional elements, such as for example at least one connection point 38 with a connection opening for supplying and discharging or scavenging the hydraulic medium, in particular hydraulic oil. There are also provided in the region of the connection opening 38a1, 38a2 fastening elements 39a, which are part of a fastening device 39 for fastening connection fittings or connection lines, for example the supply- and/or discharge line 16, 17, or a leakage line.

In the embodiments, one or two connection openings 38a1, 38a2 is/are disposed in the apex 34d of the elevation 34a and/or 34b, namely in the longitudinal region L2, in which the rear transverse wall 18a and/or the housing base 2b is situated, and/or in the longitudinal region L1 of the peripheral wall 2c. The connection opening 38a1 and/or 38a2 is formed by means of a hole that transversely penetrates the peripheral wall 2c or the housing base 2b in the apex 34d, wherein the centre line 38b of the connection opening 38a1, 38a2 and/or of the hole is situated in the bisector of the peripheral wall portions 2e and/or lateral surface portions 34e and/or includes therewith a, for example, obtuse angle W1 of ca. 135° or, given the existence of a ca. 45° fitting, an acute angle W2 of ca. 45°.

Within the scope of the invention the hole forming the connection opening 38a1 may, according to the left of FIG. 3, serve directly as a fastening element for an associated hydraulic line, for example in the sense of a threaded connection, so that the hole itself is a fastening element 39a of the fastening device 39.

The embodiment shows in FIG. 3 on the right as fastening elements 39a an attachment face 39b, which extends approximately at right angles to the centre line 38b and surrounds the connection opening 38a2, and two or more fastening holes 39c, which are disposed opposite one another, preferably in the attachment face 39b, and used for the screw connection of a connection fitting for a hydraulic line that may be placed on the attachment face 39b and screw-fastened by non-illustrated screws to the peripheral wall 2c.

The attachment face 39b and/or the connection opening 38a1 is situated preferably on and/or in a second elevation 42, which is elevated in the sense of a projection from the first elevation 34a, 34b.

A second connection opening 38a1 or 38a2 may be disposed in the region of one of the other elevations 34a, 34b that are offset in the peripheral direction, for example in the diametrically opposite elevation 34a, 34b, as is shown in FIG. 4. In this case, there may be associated with this connection opening 38a1, 38a2 identical or different fastening elements 39a of a fastening device 39 for fastening an associated hydraulic line, for example of the existing circuit.

As is evident in particular from FIG. 4, the connection fitting 38c disposed at the top right of the connection point 38 may comprise a connection element 38d for an associated line, the centre line 38e of which line extends parallel to the seating face 39b and/or parallel to the seating face of the connection fitting 38c that rests thereon and with the centre line 38b includes an approximately right angle. Given such an arrangement, the centre line 38e of the connection fitting 38c with the adjacent side wall portion 2g includes the acute angle W2 of ca. 45°.

Within the scope of the invention it is however also possible for the connection fitting 38c to be integrally connected to the elevation 34a, 34b.

Thus, independently of the previously described development of the connection points 38 for the hydraulic circuit, it is likewise advantageous to dispose a connection point 38 for a leakage line only in the at least one elevation 34a, wherein this connection point is disposed in the longitudinal region L1 of the interior 3.

The peripheral wall portions 2e of the peripheral wall 2c lead also to a widening and improvement of a seating on the side wall portions that form them, namely particularly if at least one relevant elevation 34a and/or 34b is of a, not rounded, but angular design, as is shown at the top of FIG. 3 and at the top left of FIG. 4. Such a peripheral wall portion 2e, particularly if its outer surface is flat, is suitable as an attachment face 45 for a trigger device 46 for triggering the adjusting mechanism 31a disposed in the associated interior portion 36. The trigger device 46 has connections for an electric power supply and/or hydraulic supply.

The flange 2d is detachably connected to the pot-type housing 2a by a screw connection 51 using a plurality of screws 51a, which are arranged distributed along the periphery, penetrate through-holes in the flange 2d and are screwed into threaded holes in the edge region of the peripheral wall 2c.

For fastening the axial piston engine 1 to a non-illustrated carrier, for example an engine frame, a second indicated screw connection 52 is provided, which comprises a plurality of screw holes 52a in the flange 2d, which are arranged distributed along the periphery, for example in the elevations 34c, for non-illustrated screws that may be introduced into the screw holes 52a and screwed into non-illustrated threaded holes of the carrier. The screw holes 52a may be formed by slots that are open at the periphery.

The flange 2d may serve also as an adapter for the adapted fastening of the axial piston engine 1 to different carriers (for example of different manufacturers). For such a case two flanges 2d are provided, the screw holes 51a of which are of an identical design for an identical hole pattern of an identical screw connection 51, while the two flanges 2d have screw holes 52a of different hole patterns, which are adapted in each case to the associated hole pattern of the respective carrier.

The invention is not restricted to the described embodiment and is suitable for example also for inclined-axis-type axial piston engines. All of the features of the description and/or the drawings may, within the scope of the invention, be combined in any desired manner with one another.

Claims

1. Hydrostatic axial piston engine, having wherein the peripheral wall has at least one radial elevation, which is constructed in an elongate manner in the longitudinal direction of the housing and which is formed by two peripheral wall portions, which are arranged in an angular or U-shaped manner and delimit a radially widened interior portion.

a housing, which with two transverse walls and a peripheral wall connecting these longitudinally to one another surrounds an interior,

a driving shaft, which extends longitudinally in the housing and is mounted rotatably in the housing, and

a swash plate, which is mounted longitudinally adjacent to the cylinder drum in the housing and supported against which in an articulated manner are pistons that are reciprocably mounted in approximately longitudinally extending piston holes in the cylinder drum,

2. Hydrostatic axial piston engine according to claim 1, wherein the elevation extends over the length (L1) of the interior.

3. Hydrostatic axial piston engine according to claim 1, wherein two elevations are disposed opposite one another or a plurality of elevations, for example three or four, are disposed offset relative to one another in the peripheral direction.

4. Hydrostatic axial piston engine according to claim 1, wherein the cylinder drum with its inner side remote from the swash plate rests against a cam disc disposed between it and a transverse wall and the at least one elevation extends longitudinally also over the transverse wall or over both transverse walls.

5. Hydrostatic axial piston engine according to claim 1, wherein in the apex of the elevation a hydraulic connection point with a connection opening is and/or are disposed.

6. Hydrostatic axial piston engine, having wherein, the cylinder drum rests with its side remote from the swash plate against a cam disc disposed between it and a transverse wall, wherein on the periphery of this transverse wall a radial elevation with an angular or U-shaped cross section is disposed, in the apex region of which a hydraulic connection point with a connection opening is disposed.

a housing, which with two transverse walls and a peripheral wall connecting these longitudinally to one another surrounds an interior,

a driving shaft, which extends longitudinally in the housing and is mounted rotatably in the housing, and

a swash plate, which is mounted longitudinally adjacent to the cylinder drum in the housing and supported against which in an articulated manner are pistons that are reciprocably mounted in approximately longitudinally extending piston holes in the cylinder drum,

7. Axial piston engine according to claim 6,

wherein the elevation extends at least partially longitudinally also along the peripheral wall or also along the other transverse wall.

8. Hydrostatic axial piston engine according to claim 5, wherein at the hydraulic connection point fastening elements are disposed, which are parts of a fastening device for fastening a hydraulic line or a connection fitting.

9. Hydrostatic axial piston engine according to claim 8,

wherein at the connection point at least one, preferably flat, seating face is provided.

10. Hydrostatic axial piston engine according to claim 8

wherein the fastening elements are disposed on a second elevation that is elevated from the first elevation, for example only in the region of the connection point.

11. Hydrostatic axial piston engine according to claim 1, wherein the throughput volume of the axial piston engine may be either increased or decreased by means of an adjusting device having an adjusting mechanism, and preferably the swash plate is mounted as part of the adjusting device pivotably about an oriented swiveling axis in a swivel joint.

12. Hydrostatic axial piston engine according to claim 11,

wherein the adjusting mechanism and/or a swivel-limiting device are/is of an elongate design and extend/extends transversely offset in relation to the swivelling axis in the longitudinal direction of the axial piston engine in the widened interior portion or in one of the widened interior portions.

13. Hydrostatic axial piston engine according to claim 1, wherein one or two elevations having a transversely oriented mutual spacing are disposed transversely offset in relation to the swivelling axis.

14. Hydrostatic axial piston engine according to claim 12

wherein two transversely mutually spaced-apart radial elevations with widened interior portions are disposed on both sides of the swivelling axis and preferably an adjusting mechanism and a swivel-limiting device are disposed on each side of the swivelling axis, in particular are disposed obliquely opposite one another.

15. Hydrostatic axial piston engine according to claim 4,

wherein the transverse wall is formed by the base wall of a pot-type housing.

16. Hydrostatic axial piston engine according to claim 1, wherein the housing at least in the region of the at least one elevation has a cross-sectional shape delimited by four side wall portions, in particular a square or rectangular cross-sectional shape, preferably with rounded corners.