WO2014184291A2

WO2014184291A2 - Component having at least two parts welded to each other

Info

Publication number: WO2014184291A2
Application number: PCT/EP2014/059940
Authority: WO
Inventors: Mykola Oleksyuk; Zhiming Chen
Original assignee: Schwing Gmbh
Priority date: 2013-05-16
Filing date: 2014-05-15
Publication date: 2014-11-20
Also published as: WO2014184291A3; DE102013008351B3; DE102013008351B9

Abstract

For dynamically loaded components, in particular hydraulic cylinders, that have at least one weld seam, fatigue of the weld seam and an associated loss of strength can occur over time, in particular if the root of the weld seam is heavily loaded. Fine cracks in the region of the root, for example, are a frequent cause of material failure. In order to improve the strength of rotationally symmetric, welded components, it is proposed that a narrowed web (7) is formed in a region adjacent to the weld seam (10) on a first part (2; 4) and/or on a second part (3; 5) of the component, which parts are connected to each other by means of the weld seam (10), wherein the wall thickness (t₁, t₂) of the first and/or second part (2; 4, 3; 5) in the region of the narrowed web (7) is less than the depth (t_s) of the weld seam (10). Thus, the force flow can at least partially bypass the root (11) so that the welded joint (10) is less heavily loaded.

Description

The invention relates to a component having at least two parts welded together.

Weld seams must withstand high static and / or dynamic loads in many systems or devices. This applies, for example, to hydraulic cylinders of concrete pumps, in particular hydraulic cylinders, which are subjected to a high pressure (in some cases over 350 bar). The weld between the cylinder bottom and the cylinder tube of the hydraulic cylinder is exposed in many cases high static and / or dynamic stresses. It is known that the weld is usually claimed particularly strong in the area of its weld root. The weld root is a weak point, which may be due to the geometry of the weld (notch effect), for example. A binding error or a time-forming crack in the weld root can lead to the failure of the entire weld. In part, mechanical post-processing attempts to make the weld more loadable, particularly by removing overhanging portions of the weld root, thereby eliminating the geometric notch. However, such reworking is not possible in all cases, eg due to the arrangement of the weld. In addition, the post-processing means additional effort and costs. An alternative to this is to design the weld for stronger loads than the actual loads occurring. However, a thicker weld usually requires larger material thicknesses of the components to be joined, at least in the region of the weld seam. This means a higher (material) effort, a higher energy consumption, higher costs and a higher weight of the components.

DE 1 900 951 A shows a welded connection between a cylinder head and a cylinder wall of a hydraulic cylinder, in which the weld is in a deep circumferential groove with diverging side walls and an arcuate bottom, wherein the circumferential groove is introduced into the solid material of the cylinder head. In each case one of the side walls is formed by the cylinder head and the cylinder wall. The circumferential groove extends further inward than the cylindrical surface of the cylinder head, on which the cylinder head and the cylinder wall come into contact with each other. As a result, the weld root can also be subjected to pressure when the hydraulic cylinder is loaded, which leads to a shearing stress within the weld seam. This causes a lower stress load per unit area. The weld is introduced in three or more steps in the circumferential groove, wherein the weld is gradually built up from the bottom of the circumferential groove ago.

The object of the invention is to provide a welded component which has good strength, in particular under dynamic load. At the same time the production should be as simple and inexpensive. This object is achieved by the invention by a component according to claim 1.

Advantageous developments of the invention are specified in the subclaims.

An inventive component is substantially rotationally symmetrical, ie formed symmetrically about a central longitudinal axis and has a substantially cylindrical wall, consists of at least two verschwe ßten parts and has at least one first part with a second part connecting weld having a predetermined depth and has a weld root. According to the invention it is proposed that a narrowed web is formed on the first part and / or on the second part in a region adjacent to the welding seam region of the cylindrical wall, wherein the wall thickness of the first or second part in the narrowed web is smaller than the depth of the weld. In this way, the flow of force in the weld can be guided past a possibly existing weak point in the area of the weld root. The weld root can be relieved. The stress in the weld root is reduced. In this case, the service life of an inventively designed hydraulic cylinder or the welded joint can be increased, estimated by at least 100%. A static and / or dynamic load, in particular due to changing pressures or high pressure peaks of a hydraulic fluid, can be absorbed in a material-saving manner. Also, a cost-effective production can be carried out, in particular with less material or inexpensive material.

Within the meaning of the invention, a component is to be understood as meaning any component which has to withstand high static and / or dynamic loads, the loads being transmitted at least partially through the welded connection. In the sense of the invention, weld root (or root) for short is understood to be the region of the weld in which the weld seam or a groove in which the weld seam is provided is tapered. The weld root usually represents the bottom area of the weld. In the area of the root, the least amount of welding material is present between the components to be joined.

For the purposes of the invention, a narrowed web is understood to mean a material taper, constriction or the like which is formed by a section of reduced wall thickness of the cylindrical wall in relation to the wall thickness in adjacent sections of the wall. In the sense of the invention, the region adjoining the weld seam is that region of the cylindrical wall which forms the cylindrical wall concerned part over which the power flow is introduced into the weld. This area can be located, for example, within a distance from the weld seam that corresponds at most to 10 times, preferably at most 5 times, more preferably at most 3 times the maximum width of the weld seam.

The invention is, as already mentioned, especially for welded joints in hydraulic cylinders. In this case, the first part is a cylinder tube of a hydraulic cylinder, and the second part is a cylinder bottom of the hydraulic cylinder. Likewise, the first part may be a reciprocating rod of a hydraulic cylinder, and the second part may be a rod end of the hydraulic cylinder. In these cases, the first or second part in the region of the narrowed web has an inner diameter which is greater than the inner diameter of the first or second part outside the narrowed web. Preferably, the narrowed web has an inner circumferential surface, which is arranged at least partially further out than the root of the weld. The root is thus arranged further inside than the inner circumferential surface of the narrowed web. As a result, the desired relief of the root can be done effectively. The narrowed land is provided on the second part, i. at the cylinder bottom or at the rod end. In other words, the narrowed web is seen from the first part beyond the welded joint.

Preferably, the weld joint is formed as a single circumferential weld. As a result, a good strength and a symmetrical load can be achieved. Preferably, the wall thickness of the first or second part in the region of the narrowed web is approximately 75-95% of the weld depth,

According to an advantageous embodiment, the narrowed web is formed by a milled recess or by an undercut. A milled recess or an undercut provides the advantage of a simple and inexpensive and low-voltage design of the web. Preferably, the narrowed web or the recess is formed chamfered. As a result, among other things, the risk of breakage in the region of the cylinder bottom can be reduced. The narrowed web or the recess is particularly preferably formed so that the wall thickness decreases in this area in the direction of the weld. Advantageously, the web is beveled by about 5-25 °, preferably by about 10-20 °, more preferably by about 14 °.

According to an advantageous embodiment, the first or second part has a projection which overlaps the weld seam (a so-called weld pool lock), wherein the projection preferably overlaps the weld seam on the inside of the weld root. The weld pool on the one hand has the function to seal off the weld against the interior of the cylinder so that no weld metal can penetrate the cylinder during the welding process, on the other hand, the extension has a centering effect during assembly before the welding process.

According to a further advantageous embodiment, the component has two narrowed webs adjacent to the weld seam, wherein in each case a narrowed web is provided on each of the two parts. As a result, the targeted passage of the power flow at the root can be done in an even more effective manner.

With reference to the drawings embodiments of the invention will be explained below.

Show it:

Figure 1 is a sectional side view of a schematic representation of a hydraulic cylinder having a weld in the region of a cylinder base or in the region of a rod head;

Figure 2a in a detailed view according to the indicated in Fig. 1 detail A is a schematic Representation of a weld according to the prior art;

FIG. 2b shows in a further detail view according to the detail A indicated in FIG. 1 a 5 schematic representation of a processed weld seam according to the prior art;

FIG. 3 shows, in a detailed view according to detail A indicated in FIG. 1, a schematic representation of a weld seam according to a first exemplary embodiment of the invention;

FIG. 4 shows, in a detail view according to detail A indicated in FIG. 1, a schematic representation of a weld seam according to a second exemplary embodiment of the invention;

FIG. 5 shows, in a detail view according to detail A indicated in FIG. 1, a schematic representation of a weld seam according to a third exemplary embodiment of the invention;

FIG. 6 shows in a detail view according to the detail A indicated in FIG. 1 a schematic representation of a weld seam according to a fourth exemplary embodiment of the invention; and

FIG. 7 shows in a detail view according to the detail A indicated in FIG. 1 a schematic representation of a weld seam according to a fifth exemplary embodiment of the invention.

FIG. 8 shows in a detailed view according to the detail A indicated in FIG

35 Representation of a weld according to a sixth embodiment of the

Invention.

In Fig. 1, a hydraulic cylinder 1 is shown, which has a cylinder tube 2 and a piston rod 4 arranged therein. The cylinder tube 2 is connected by means of a weld 10 'with a cylinder bottom 3, and the Hubkolbenstange 4 is connected by means of a weld 10' with a rod head 5. The hydraulic cylinder 1 extends along a central longitudinal axis M.

In Fig. 2a, the indicated in Fig. 1 detail A is shown. Fig. 2a shows the arrangement and structure of the weld 10 'according to the prior art. The cylinder tube 2 has a wall thickness t, and the weld seam 10 'is provided on an end face of the cylinder tube 2 and formed over the entire depth or wall thickness t of the cylinder tube 2. The weld 10 'has a weld root 1 1', which is arranged in a region in which the cylinder bottom 3 is adjacent to the cylinder tube 2.

In Fig. 2b, a variant of the welded connection according to the prior art is shown. The weld 10 'is slightly spaced from the cylinder bottom 3, i. arranged in the region of the wall of the hydraulic cylinder 1. Before a post-processing step, the weld root 1 1 'in the region of the inner circumferential surface 12 a of the cylinder tube 2 is arranged. The inner circumferential surface 12a, 12b of the cylinder tube 2 has been machined after Verschwei Shen by material removal, so that the wall thickness t of the cylinder tube 2 after machining is smaller. The weld root 1 1 'is less pointed in this case after machining. It is flattened by the machining, so that less voltage peaks arise.

The following statements on the welded connection or interface between cylinder tube 2 and cylinder bottom 3 (corresponding to detail A) apply equally to a welded joint or interface between the reciprocating rod 4 and the rod head 5 (corresponding to the region of the detail B indicated in FIG. 1). In Fig. 3, the weld 10 with welding root 1 1 is shown, which is arranged between the cylinder tube 2 (first part) and the cylinder bottom 3 (second part). The first part 2 has an inner diameter D and a wall thickness t, and the second part 3 has a cylinder portion 3a, 5a on which has an inner diameter D1 and a wall thickness ti. According to the invention, the following size ratios apply: D1> D and ti <t. The cylinder portion 3a, 5a, which forms part of the cylindrical wall of the hydraulic cylinder 1, is designed in sections as a narrowed web 7, which has a wall thickness which is smaller than the thickness ts of the welded joint 10, ie smaller than the depth t _{s of} the weld 10. The narrowed web 7 may also be referred to as a recess or undercut which is introduced, for example by means of milling or turning. On the cylinder portion 3a, 5a, a weld root 1 1 overlapping extension 3.1, 5.1 is also provided. The undercut 7 has a side wall 7.1, which merges into the extension 3.1, 5.1. The side wall 7.1 is formed at least approximately parallel to the side wall of the groove for the weld 10.

By the wall thickness t1 smaller than the wall thickness t and the thickness t _{s of} the weld 10 is selected, according to the invention, the power flow over the weld root 1 1 can be reduced. It is important that the narrowed web 7 is formed on the cylindrical wall, that is not on the left in Fig. 3 bottom wall of the cylinder, which is perpendicular to the cylindrical wall. Thus, the longitudinal extension of the web 7 is substantially parallel to the power flow. FIG. 4 shows a variant in which the wall thickness ti is approximately equal to the thickness t _{s of} the weld seam 10 or the wall thickness t. On the cylinder portion 3a, 5a no narrowed web is formed, this is rather on the first part 2, 4 before, especially in the form of an arcuate recess 7. The recess or the narrowed web 7 has at the lowest point an inner diameter D ₂ and a wall thickness t ₂ and has an arcuate cross-section. The following proportions apply: D ₂ > D and t ₂ <t. Also in this variant, the power flow over the weld root 1 1 is reduced. As in the embodiment of the 3, the flow of force on one side of the weld 10 is narrowed by means of the narrowed web 7.

5, a variant is shown in which a weld root 1 1 overlapping extension is not provided. However, the weld root 1 1 is exposed here. The following proportions apply:

6, a variant is shown in which in a modification of the embodiment of FIG. 4, a weld root 1 1 overlapping extension is not provided. The following proportions apply: D ₂ > D and t ₂ <t.

FIG. 7 shows a variant in which, on both sides of the weld seam 10, a narrowed web 7 is provided in connection with an extension 3.1, 5.1. In this case, the force flow is indicated by K, which is narrowed by both narrowed webs 7 and at least approximately parallel to the outer and inner circumferential surface of the first part 2, 4 and second part 3, 5 runs. The following proportions apply: D> D and D ₂ > D and ti <t and t ₂ <t.

In Fig. 8, a variant is shown, in which the narrowed web 7 is formed chamfered. This can reduce the risk of breakage. The narrowed web 7 is formed so that the wall thickness t ₂ decreases in this area in the direction of the weld 10. The narrowed web 7 has, on the side facing away from the weld seam 10, an inner diameter D _a and a side facing the weld seam 10 on an inner diameter D _z , wherein the diameter D _a <D _z .

- List of Reference Signs - LIST OF REFERENCE NUMBERS

1 hydraulic cylinder

2 first part, in particular cylinder tube or cylinder wall

2a cylinder inner wall before a surface treatment

2b Cylinder inner wall after a surface treatment

3 second part, in particular cylinder bottom

3.1 overlapping extension

3a cylinder section

4 first part, in particular piston rod

5 second part, in particular rod end

5.1 overlapping extension

5a cylinder section

7 recess or solid joint or narrowed web or

Freeway

7a inner lateral surface of the recess

7.1 side wall of the recess

10 'weld according to the prior art

1 1 'weld root according to the prior art

10 weld

1 1 weld root

12a inner lateral surface before processing

12b Inner circumferential surface after machining

D inside dimension, in particular inside diameter of the first part

D1 inner dimension, in particular inner diameter of the second part in the region of the narrowed web

D2 inner dimension, in particular inner diameter of the first part in the region of the narrowed web t wall thickness of the first part, eg a cylinder wall or a

lifting piston rod

t1 Thickness of the second part in the area of the narrowed web

t2 Thickness of the first part in the area of the narrowed web

ts depth of the weld

K power flow through weld

M Center longitudinal axis of the hydraulic cylinder

- Claims -

Claims

claims

1 . Component with at least two parts welded together (2, 3, 4, 5), with

a first part (2; 4),

a second part (3; 5),

at least one weld seam (10) connecting the first part (2; 4) to the second part (3; 5) and having a predetermined depth (ts) and a root (1 1),

wherein the component is formed substantially symmetrically about a central longitudinal axis (M) and has a substantially cylindrical wall, characterized in that on the first part (2; 4) and / or on the second part (3; Weld seam (10) adjacent region of the cylindrical wall a narrowed web (7) is formed, wherein the wall thickness (t1, t2) of the first or second part (2; 4, 3; 5) in the narrowed web (7) smaller is the depth (ts) of the weld (10).

2. Component according to claim 1, characterized in that the first part (2) is a cylinder tube of a hydraulic cylinder, and the second part (3) is a cylinder bottom of the hydraulic cylinder.

3. Component according to claim 1, characterized in that the first

Part (4) is a Hubkolbenstange (4) of a hydraulic cylinder, and the second part (5) is a rod head (5) of the hydraulic cylinder.

4. Component according to one of claims 1 to 3, characterized in that the first or second part (2, 4, 3, 5) in the region of the narrowed web (7) has an inner diameter (D1, D2), the is greater than the inner diameter (D) of the first or second part (2, 4, 3, 5) outside the narrowed web (7).

5. Component according to one of claims 1 to 4, characterized in that the narrowed web (7) is formed by a milled recess or by an undercut.

6. Component according to one of the preceding claims, characterized in that the weld seam (10) is circumferential, wherein the depth (ts) of the weld seam (10) is substantially equal to the wall thickness of the first or second part (2, 4, 3; 5).

7. Component according to one of the preceding claims, characterized in that the first or second part (2, 4, 3, 5) has a weld (10) overlapping extension (3.1, 5.1), wherein the extension (3.1, 5.1) the weld (10) preferably inside, ie on the side of the weld root (1 1) overlaps.

8. Component according to one of the preceding claims, characterized in that the narrowed web (7) is formed chamfered.

- Summary -