PISTON ROD UNIT, HYDRAULIC CYLINDER AND ANGLED STEAM

Description

[0001] The invention relates to a piston rod unit for a hydraulic cylinder, having at least one piston-side end piece and at least one rod-eye-side end piece, a hollow piston rod which is arranged between the end pieces, wherein a cavity formed in the piston rod extends at least into at least one of the end pieces, as well as to a hydraulic cylinder having such a piston rod unit, and to an articulated mast of a large manipulator having such a hydraulic cylinder.

[0002] Such a piston rod unit is known from DE 10 2013 008 351 B3 or EP 1 346 157 B1.

[0003] From WO 2007 / 139384 A1, FR 2 224 659 A1 and EP 3 133 298 A1, corresponding piston rod units are known in which a plug is additionally inserted into the cavity, which plug supports the piston rod and / or an end piece on the cavity side.

[0004] To reduce the weight of hydraulic cylinders, the piston rods are now typically hollow, particularly in hydraulic cylinders on articulated booms of truck-mounted concrete pumps. The remaining wall thickness of the hollow piston rods is designed to allow the required tensile and compressive forces to be transmitted by the piston rod. The connection area between the hollow piston rod and the rod-eye end piece with the bolt receptacle for connecting the piston rod to a boom segment of the articulated boom is a particularly critical area, as the rod-eye end piece deforms under the very high tensile and compressive forces to be transmitted, and this deformation is also transmitted to the connection area with the hollow piston rod.This initially leads to elastic deformation of the hollow piston rod in the connection area, which is particularly evident in a change in the cross-section of the hollow piston rod. With continuous overstressing, it cannot be ruled out that overload phenomena such as cracks may occur in the transition area between the hollow piston rod and the end piece, necessitating replacement of the entire piston rod.

[0005] Increasing the wall thickness in the connection area to prevent overloading of the hollow connection area would be the most obvious solution. However, this would increase the weight of the piston rod unit, even though this increased wall thickness is not necessary for the actual transmission of tensile and compressive forces. In addition to the weight requirements, the options for reinforcing the connection area are also limited due to the available installation space.

[0006] The object of the invention is therefore to provide an improved piston rod unit that allows for reinforcement of the hollow piston rod without significantly increasing the weight of the entire unit. The primary objective is to reduce load-related elastic deformations of the piston rod and the end pieces. In particular, a lightweight hydraulic cylinder and an articulated mast with reduced weight are to be provided.

[0007] This object is achieved by a piston rod unit having the features of claim 1 and claim 5 as well as a hydraulic cylinder according to claim 12 and an articulated mast according to claim 13.

[0008] One aspect of the present invention is provided by a piston rod unit according to claim 1. According to the invention, the plug supports the piston rod in a connection area with an end piece through which the hollow space extends. By supporting the connection area on the plug inserted into the cavity, a selective reinforcement of the connection area can be achieved, in which elastic deformations are particularly critical, since these lead to cracks more quickly here. By supporting the connection area on the plug, the connection area between the hollow piston rod and the end piece is stabilized against elastic deformations. Furthermore, the invention provides that a welded connection is formed in the connection area between the piston rod and the end piece, wherein the plug covers the area of ​​the welded connection on the cavity side, viewed in the axial direction of the piston rod.By covering the welded joint area in the axial direction of the piston rod, elastic deformation of the welded joint between the piston rod and the end piece in the connection area can be effectively prevented by the plug supporting the cavity, thus preventing permanent damage to the weld seam formed there. This makes it easy to reinforce the hollow piston rod without significantly increasing the weight of the entire piston rod unit. To reinforce the hollow piston rod, a plug is simply inserted into the cavity formed in the piston rod. The end piece, into which the cavity formed in the piston rod extends, can also be supported on the cavity side and thus reinforced by inserting the plug.This reinforcement minimizes or virtually eliminates the elastic deformation of the hollow piston rod, which occurs, for example, in the connection area between the end piece and the piston rod, thus preventing permanent damage. The plug provides a simple way to achieve selective reinforcement of the piston rod unit by supporting the piston rod and / or the end piece on the cavity side against the plug inserted into the cavity.

[0009] Advantageous embodiments and further developments of the invention emerge from the dependent claims. It should be noted that the features listed individually in the claims can also be combined with one another in any technologically expedient manner, thus revealing further embodiments of the invention.

[0010] Particularly preferred is an embodiment in which the wall thickness of the piston rod in the connecting area supported by the plug is the same as in the remaining areas of the piston rod penetrated by the cavity. With the same wall thickness of the piston rod both in the connecting area supported by the plug and in the remaining areas of the piston rod penetrated by the cavity, the weight of the piston rod unit can be effectively reduced, with the selective reinforcement in the connecting area supported by the plug being sufficient to reduce elastic deformations of the piston rod unit to such an extent that these do not lead to permanent damage.

[0011] A particularly advantageous embodiment of the invention relates to the plug being constructed in two parts, wherein a first part of the plug is arranged in the connection area between the piston rod and the end piece and a second part of the plug is arranged in the end piece. By dividing the plug into at least two plug parts, individual areas of the piston rod unit can be specifically supported on the cavity side. The first part of the plug preferably supports the connection area between the piston rod and the end piece, thereby preventing load-related, elastic deformations. The second part of the plug, on the other hand, can be arranged in the end piece and effectively prevent elastic deformations of the end piece by supporting it on the cavity side by the plug part.

[0012] An advantageous embodiment of the invention provides that the rod-eye end piece has two laterally projecting pipe sockets, with the plug being arranged between the pipe sockets in the hollow space developed here. By arranging the plug between the two laterally projecting pipe sockets of the rod-eye end piece, effective reinforcement can be achieved, which reduces deformation of the rod-eye end piece. By reducing the deformation in the laterally projecting pipe sockets of the rod-eye end piece, further deformation of the hollow piston rod is also minimized, since less deformation is transferred from the end piece to the connected piston rod.

[0013] Furthermore, a further aspect of the present invention is provided by a piston rod unit according to claim 5. The arrangement of the plug between the two laterally projecting pipe sockets of the rod-eye end piece provides reinforcement that reduces deformation of the rod-eye end piece. By reducing the deformation in the laterally projecting pipe sockets of the rod-eye end piece, further deformation of the hollow piston rod is also minimized, since less deformation is transferred from the end piece to the connected piston rod.

[0014] A particularly advantageous embodiment is one in which the plug has a through-bore through which a hinge pin is guided on the rod-outside end piece. By passing the hinge pin through the plug, effective guidance of the hinge pin can be achieved at the rod-outside end piece, which, on the one hand, minimizes deformation of the pin and, on the other hand, simply secures the plug in the rod-outside end piece.

[0015] An advantageous embodiment provides for the plug to be made of the same material as the piston rod, preferably steel. Since the hollow piston rod is only reinforced at specific points by the plug, the use of a corresponding plug still results in a significant weight advantage compared to a solid piston rod made of the same material. The plug is preferably made of steel, as this material has high compressive strength.

[0016] According to a preferred embodiment of the invention, the plug is made at least partially of light metal, preferably aluminum. By reinforcing the piston rod unit with a plug made of light metal, point support is possible without significantly increasing the weight of the piston rod unit. The plug is preferably made of aluminum because this material has high compressive strength and a low specific gravity. The specific gravity of aluminum is approximately one-third of the specific gravity of steel, thus enabling a very effective increase in rigidity in highly stressed areas of the piston rod unit, even though the overall weight of the piston rod unit is only insignificantly increased by the plug. The plug can also be made of another rigid material that has sufficient compressive strength.

[0017] A particularly advantageous embodiment provides that at least one annular sealing element creates a seal between the plug and an inner wall of the cavity. To prevent external dirt from penetrating the rod-eye-side spherical plain bearing and to prevent grease from the lubrication of the pivot pin from entering the hollow piston rod, annular sealing elements are provided between the plug and an inner wall of the cavity. The annular sealing elements can be accommodated in grooves, which are preferably screwed into the plug. The sealing elements are preferably designed as O-rings.

[0018] An advantageous embodiment provides for the plug to be screwed to the end piece containing the cavity via a screw connection on the head side. The plug can be easily secured in the cavity in the end piece via the screw connection on the head side. The screw connection on the head side preferably comprises a retaining plate that is screwed to the plug on the head side and is attached to the end piece via screw connections.

[0019] A particularly advantageous embodiment of the invention provides that the plug is supported on a shoulder formed in the cavity. By supporting the plug on a shoulder formed in the cavity, the plug can be easily secured in the cavity. The plug can easily rest on the shoulder, thus enabling the piston rod and end piece to be supported on the cavity side at a fixed position in the cavity.

[0020] Furthermore, the invention relates to a hydraulic cylinder with a piston rod unit as described above and in more detail below. A hydraulic cylinder equipped with such a piston rod unit not only has a lower weight but also a high load capacity, since the piston rod unit, reinforced at specific points by the plug, can absorb greater forces without its weight being significantly increased by the plug.

[0021] Furthermore, the subject of the invention is an articulated mast of a large manipulator, in particular a truck-mounted concrete pump, having a plurality of mast segments, wherein the mast segments are each pivotable about articulated axes at articulated joints relative to an adjacent mast segment or a bolster, wherein at least one hydraulic cylinder as described in more detail above and below effects a pivoting movement in at least one articulated joint.

[0022] The demands on the mast length, i.e., the reach of the articulated booms of large manipulators such as truck-mounted concrete pumps, are constantly increasing. To keep the overall weight of the articulated booms as low as possible, particularly lightweight hydraulic cylinders are advantageous. The use of lightweight hydraulic cylinders reduces the weight of the articulated booms, allowing for greater reach.

[0023] Further features, details, and advantages of the invention will become apparent from the following description and from the drawings, which show exemplary embodiments of the invention. Corresponding objects or elements are provided with the same reference numerals in all figures. They show: Figure 1: Large manipulator with articulated mast according to the invention, Figure 2: Hydraulic cylinder according to the invention, Figure 3: Piston rod unit according to the invention, Figure 4: Sectional view of the piston rod unit, Figure 5: Detailed sectional view under pressure load on a piston rod unit according to the prior art, Figure 6: Detailed sectional view of a piston rod unit according to the invention, Figure 7: Piston rod unit according to the invention with plug and Figure 8: Detailed sectional view of the piston rod unit according to the invention with two-part plug.

[0024] In the Figure 1Denoted by the reference numeral 17, an articulated mast 17 according to the invention is shown on a large manipulator 18 designed as a truck-mounted concrete pump. The articulated mast 1 is mounted on a turntable 21 which is rotatable about a vertical axis 22 and which mounts the articulated mast 17 relative to the chassis 23 of the large manipulator 18 in a rotatable and pivotable manner via an articulated joint 20. The articulated mast 17 has several mast segments 19 which are pivotable in articulated joints 20 about articulated axes relative to an adjacent mast segment 19 or the turntable 21. For pivoting the mast segments 19, hydraulic cylinders 2 are assigned to each of the articulated joints 20, which cause the pivoting movement of the mast segments 19 in the articulated axes. Via this pivoting movement, the Figure 1The articulated mast 17, shown folded, can be unfolded. In the unfolded state of the articulated mast 17, liquid concrete fed via the feed hopper 24 can be conveyed by means of a thick matter pump unit in the truck-mounted concrete pump through the concrete delivery lines 25 arranged on the articulated mast 17, within the reach of the articulated mast 17, to the point of use on the construction site.

[0025] The Figure 2 shows a hydraulic cylinder 2 according to the invention, as shown in Figure 1 assigned to the articulated joints 20 of the articulated mast 17, in a single view. In this single view, the piston rod unit 1 is shown retracted into the cylinder body 26 of the hydraulic cylinder 2, so that only the rod-eye end piece 4 protrudes from the cylinder body 26.

[0026] With Figure 3 is a detailed view of the piston rod unit 1 according to Figure 2This piston rod unit 1 according to the invention has a piston-side end piece 3, on which a piston 27 is arranged. Furthermore, the piston rod unit 1 has a rod-eye-side end piece 4. The rod-eye-side end piece 4 has two laterally projecting pipe sockets 9, 10. A joint pin 12 ( Fig. 5 ) for connecting the hydraulic cylinder 2 to a mast segment 19. The end pieces 3, 4 of the piston rod unit 1 are connected to each other via a piston rod 5.

[0027] The Figure 4 shows the piston rod unit 1 according to Figure 3in a sectional view. This sectional view allows a view into the hollow piston rod 5 of the piston rod unit 1. In this illustration, it is clearly visible that the cavity 6 formed in the piston rod 5 extends at least as far as the rod eye-side end piece 4. In the connecting area 8 between the piston rod 5 and the end piece 4, a welded joint 28 is indicated, with which the piston rod 5 is connected to the end piece 4. The piston rod 5 has the same wall thickness d in the connecting area 8 as in the other areas of the piston rod 5 through which the cavity 6 passes. As in Figure 4As can be seen further, the piston rod unit 1 has a plug 7 which is inserted into the cavity 6 and supports the piston rod 5 and the rod eye-side end piece 4 on the cavity side, i.e. from the inside. The plug 7 projects into the cavity 6 so far into the piston rod 5 that the connecting area 8 of the piston rod 5 with the end piece 4 is supported by the plug 7. The plug 7 thus supports the connecting area 8, in which the piston rod 5 has the same wall thickness d as in the other areas penetrated by the cavity 6. This enables the connecting area 8 between the hollow piston rod 5 and the rod eye-side end piece 4 to be reinforced at specific points by the plug 7 inserted in the cavity 6. The specific reinforcement prevents, in particular, elastic deformations in the area of ​​the welded connection 28 between the piston rod 5 and the end piece 4.For this purpose, the plug 7 covers the area of ​​the welded joint 28 on the cavity side, as seen in the axial direction of the piston rod 5. As shown in . Figure 4As can also be seen, the plug 7 is arranged between the pipe sockets 9, 10 of the end piece 4 in the cavity 6 developed here. In order to form the cavity 6 in the hollow piston rod 5 and for machining the weld seam 28 between the hollow piston rod 5 and the rod eye-side end piece 4, the cavity 6 between the two pipe sockets 9, 10 of the end piece 4 is accessible. From this access, the plug 7 is inserted into the cavity 6. The cavity 6, or the hollow piston rod 5 and the end piece 4, can be smoothly turned or drilled on the inside and the diameter of the plug 7 is preferably machined to fit so that the plug 7 can be easily inserted. This sufficiently stabilizes the piston rod 5, or the connecting area 8, from the inside, i.e. on the cavity side.The plug 7 is then screwed to the rod-eye end piece 4 via a head-side screw connection 15. In this way, the position of the plug 7 in the end piece 4 is easily fixed. The plug 6 can also be held in position by the hinge pin 12 alone. After loosening the screw connection 15 or removing the hinge pin 12, the plug 7 can be easily removed from the cavity 6. The plug 7 is thus designed to be removable from the cavity 6. This allows the piston rod unit 1 to be inspected for damage from the inside, i.e., from the cavity side, after extended operation of the hydraulic cylinder 2.

[0028] In addition, the piston rod unit 1 can be manufactured with or without the plug 7, depending on the expected load, or the plug 7 can also be easily installed later.

[0029] The Figure 5shows a detailed sectional view of a piston rod unit 1 according to the prior art under compressive load on the joint pin 12. The forces introduced by the joint pin 12 into the end piece are indicated as vertical block files, which ultimately cause a deformation of the joint pin 12 and the end piece 4 with the projecting pipe sockets 9, 10. These deformations lead to a deformation of the hollow piston rod 5 in the connecting area 8 between the piston rod 5 and the end piece 4, which is indicated by horizontal arrows. The force curve under compressive load is indicated by further diagonally running block files. Under a tensile load on the joint pin 12 (indicated bottom right), it deforms in the opposite direction, which leads to a correspondingly opposite deformation of the end piece 4. This opposite deformation continues via the connecting area 8 in the hollow piston rod 5.The opposing deformations lead to material fatigue in the long term and, in the worst case, to the breakage of the connection between end piece 4 and piston rod 5.

[0030] The Figure 6 shows a detailed sectional view through the piston rod unit 1 according to the invention Figure 4 The plug 7 inserted into the cavity 6 is in Figure 7 can also be seen in perspective in a single view. In this single view it is clearly visible that the plug 7 has a through hole 11 through which the hinge pin 12 ( Fig. 5 ) is guided on the rod end piece 4. For this purpose, the plug 7, as shown in Figure 6 visible, inserted into the cavity 6 in such a way that the through hole 11 is aligned with the laterally projecting pipe sockets 9, 10. The hinge pin 12 ( Fig. 5) on the rod end piece 4. The aligned arrangement of the plug 7 is also ensured by the head-side screw connection 15 of the plug 7 on the rod end piece 4. Between the plug 7 and the inner wall 14 of the cavity 6, annular sealing elements 13 are provided, which create a seal between the plug 7 and the cavity wall 14. The first, upper sealing element 13 prevents dirt from penetrating the rod end joint bearing from the outside. The second, lower sealing element 13 prevents grease from the lubrication of the joint pin 12 ( Fig. 5 ) into the hollow piston rod 5. The annular sealing elements 13 are arranged in grooves screwed into the plug. The annular sealing elements 13 are O-rings.

[0031] Out of Figure 8An embodiment emerges in which the plug 7a, 7b is constructed in two parts. A first part 7a of the plug 7 is arranged in the connecting area 8 between the piston rod 5 and the rod-side end piece 4. The second part 7b of the plug 7 is arranged only in the end piece 4. The division of the plug 7 into the two plug parts 7a, 7b enables a targeted cavity-side support of individual areas of the piston rod unit 1. The first part 7a of the plug 7 supports the connecting area 8 between the piston rod 5 and the rod-side end piece 4 in such a way that load-related, elastic deformations, in particular due to compressive loads of the hinge pin 12 ( Fig. 5), can be prevented. The second part 7b of the plug 7, however, effectively prevents elastic deformation of the end piece 4 due to its arrangement in the end piece 4 under tensile loads on the hinge pin 12 (Fig. 12) by supporting the latter on the cavity side by the plug part 7b. The plug 7 or the plug parts 7a, 7b are not force-locked to the hollow piston rod 5, which means in particular that it is not intended for the plug 7, 7a, 7b itself to transmit tensile forces. The tensile forces are transmitted, as before, only via the hollow piston rod 5. In Figure 8A small shoulder 16 can also be seen, which is formed in the cavity 6 and supports the lower plug part 7a. This fixes the lower plug part 7a in the cavity 6 of the piston rod 5. The design of the two-part plug 7a, 7b is particularly suitable for small hydraulic cylinders, because the area of ​​the bolt passage does not have sufficient material for a through hole 11 ( Fig. 7 ).

[0032] In addition to the shown support of the rod eye end piece 4 and the connecting area 8 between the rod eye end piece 4 and the hollow piston rod 5, the plug 7, 7a, 7b can also be used to support the piston side end piece 3 and the connecting area between the piston side end piece 3 and the hollow piston rod 5. List of Bezuas characters

[0033] 1Piston rod unit 2Hydraulic cylinder 3Piston-side end piece 4Rod-eye end piece 5Piston rod 6Cavity 7Plug, 7a, 7b plug parts 8Connection area 9First pipe socket 10Second pipe socket 11Through hole 12Pivot pin 13Sealing element 14Inner wall 15Head-side screw connection 16Step 17Articulated mast 18Large manipulator 19Mast segment 20Articulated joint 21Short 22Vertical axis 23Chassis 24Feed hopper 25Concrete conveyor line 26Cylinder body 27Piston 28Welded connection dWall thickness

Claims

1. Piston rod unit (1) for a hydraulic cylinder (2), comprising - at least one piston-side end piece (3), and - east one rod-eye-side end piece (4), - a hollow piston rod (5), which is arranged between the end pieces (3, 4), wherein a cavity (6) formed in the piston rod (5) extends at least into at least one of the end pieces (3, 4), wherein a plug (7, 7a, 7b) is inserted into the cavity (6), which supports the piston rod (5) and / or one of the end pieces (3, 4) on the cavity side, wherein the plug (7, 7a, 7b) supports the piston rod (5) in a connection region (8) to one of the end pieces (3, 4) through which the cavity (6) extends, wherein a welded joint is formed in the connection region (8) between the piston rod (5) and one of the end pieces (3, 4), characterised in that the plug (7, 7a, 7b) covers the region of the weld joint on the cavity side when viewed in the axial direction of the piston rod (5).

2. Piston rod unit (1) according to claim 1, characterised in that the wall thickness (d) of the piston rod (5) in the connection region (8) supported by the plug (7, 7a, 7b) is the same as in the other regions of the piston rod (5) which the cavity (6) penetrates.

3. Piston rod unit (1) according to claim 1 or 2, characterised in that the plug (7) is constructed in two parts, wherein a first part (7a) of the plug (7) is arranged in the connection region (8) between the piston rod (5) and the end piece (3, 4) and a second part (7b) of the plug (7) is arranged in the end piece (3, 4).

4. Piston rod unit (1) according to any of claims 1 to 3, characterised in that the rod-eye-side end piece (4) comprises two laterally projecting pipe sockets (9, 10), wherein the plug (7, 7a, 7b) is arranged between the pipe sockets (9, 10) in the cavity (6) continued here.

5. Piston rod unit (1) for a hydraulic cylinder (2), comprising - at least one piston-side end piece (3), and - at least one rod-eye-side end piece (4), - a hollow piston rod (5), which is arranged between the end pieces (3, 4), wherein a cavity (6) formed in the piston rod (5) extends at least into at least one of the end pieces (3, 4), wherein a plug (7, 7a, 7b) is inserted into the cavity (6), which supports the piston rod (5) and / or one of the end pieces an end piece (3, 4) on the cavity side, wherein the rod-eye-side end piece (4) comprises two laterally projecting pipe sockets (9, 10), wherein the plug (7, 7a, 7b) is arranged between the pipe sockets (9, 10) in the cavity (6) continued here.

6. Piston rod unit (1) according to any of the preceding claims, characterised in that the plug (7, 7a, 7b) comprises a through-hole (11), through which a hinge pin (12) on the rod-eye-side end piece (4) is guided.

7. Piston rod unit (1) according to any of the preceding claims, characterised in that the plug (7, 7a, 7b) is made of the same material as the piston rod (5), preferably steel.

8. Piston rod unit (1) according to any of claims 1 to 6, characterised in that the plug (7, 7a, 7b) is made of light metal, preferably aluminium, at least in part.

9. Piston rod unit (1) according to any of the preceding claims, characterised in that at least one annular sealing element (13) brings about sealing between the plug (7, 7a, 7b) and an inner wall (14) of the cavity (6).

10. Piston rod unit (1) according to any of the preceding claims, characterised in that the plug (7, 7a) is screwed to the end piece (3, 4) comprising the cavity (6) via a head-side screw connection (15).

11. Piston rod unit (1) according to any of the preceding claims, characterised in that the plug (7, 7b) is supported on a shoulder (16) formed in the cavity (5).

12. Hydraulic cylinder (2) comprising a piston rod unit (1) according to any of the preceding claims.

13. Articulated boom (17) of a large manipulator (18), in particular of an auto concrete pump, comprising a plurality of boom segments (19), wherein the boom segments (19) are each pivotable at articulated joints (20) about articulation axes relative to an adjacent boom segment (19) or a turntable (21), wherein at least one hydraulic cylinder (2) according to claim 12 brings about a pivoting movement in at least one articulated joint (20).