CYLINDER TUBE ASSEMBLY AND METHOD FOR MANUFACTURING THE SAME

Description

[0001] The invention relates to a cylinder tube assembly, in particular the connection of a cylinder tube with a connecting piece, and a method for its production.

[0002] The state of the art describes various options for connecting a connecting piece to a cylinder tube. Screw connections are possible, while bonded connections, such as welding, are also known.

[0003] A screw connection is usually designed with an internal thread in the cylinder tube and a matching external thread on the connecting piece. The internal thread in the cylinder tube is usually introduced as a radial bore orthogonal to the cylinder axis. The disadvantage of this solution is that the screw-in area on the cylinder tube must have a minimum thread depth to ensure sufficient mechanical strength of the threaded connection. This requires the cylinder tube area to have a thicker wall or be extensively machined. A thicker wall is also counterproductive for material-efficient design.

[0004] Alternatively, the connecting piece can be welded directly to the cylinder tube. Conventional welding processes, such as TIG, MAG, or laser welding, are suitable for this. A welding filler metal is usually added to bridge the joint gaps created by the outer curvature of the cylinder tube. Another known option is to mill off the outer curvature, but this is disadvantageous due to a localized weakening of the cylinder tube's cross-section. Another disadvantage of these welding processes is the high heat input into the cylinder tube material. This leads to structural changes that adversely affect strength. Furthermore, there is a risk of unwanted deformation of the cylinder tube in this section.

[0005] Another disadvantage is that the holes or threads for the pressure medium connection or flow are created by machining, such as drilling or milling. The resulting chips and dust can become trapped inside the cylinder and, during subsequent operation of the power cylinder, contaminate the oil and other peripheral components, such as valves, etc. To prevent this, extensive cleaning is required.

[0006] In addition, it is disadvantageous in all of the known solutions listed above that the passage point of the bore to the inner cylinder surface forms a contour that leads to increased wear of seals or guides on the piston or that has to be reworked at great expense to avoid such undesirable effects.

[0007] Furthermore, a solution is known from JP S53 113954 A in which the cylinder tube has a punched hole as a connection bore, with a concave bulge embossed into the inside of the cylinder tube. The disadvantage is that the bulge on the cylinder tube leads to a corresponding bulge on the outside, so that the connection piece must be designed with a beaded edge in order to be able to weld it to the outer shell side of the cylinder tube.

[0008] The object of the invention is to overcome the disadvantages of the prior art and to provide a high-quality and highly resilient cylinder tube assembly consisting of a cylinder tube with a connecting piece arranged thereon, which can also be manufactured in a time-saving and cost-effective manner.

[0009] The problem is solved with respect to the cylinder tube assembly by the features listed in patent claim 1 and with respect to the method for its production by the features listed in patent claim 7. Preferred developments arise from the respective subclaims.

[0010] The cylinder tube assembly has a cylinder tube and a connecting piece as basic components.

[0011] A cylinder tube is understood to mean any hollow cylindrical casing of a hydraulic or pneumatic assembly, which is preferably a cylinder tube of a hydraulic working cylinder or a cylinder tube of a hydraulic valve, in particular a hydraulic control valve or check valve.

[0012] In the case of a cylinder tube of a hydraulic working cylinder, the piston unit is arranged axially displaceably within the cylinder tube. To move the piston unit within the housing, the cylinder tube is pressurized with a pressure medium. According to the cylinder tube assembly according to the invention, the pressure medium is introduced or discharged laterally through the cylinder tube.

[0013] According to the invention, the cylinder tube has a cylinder base body and a connecting section.

[0014] The basic cylinder body is understood to be the tubular basic structure of the cylinder tube.

[0015] The fluid is guided via the connecting section, which is part of the cylinder tube, into the pressure medium working chamber formed by the cylinder tube, also referred to as the cylinder channel chamber. The connecting section, in turn, has an outer shell cap, which is arranged on the cylinder tube outer shell, and an inner shell cap, which is arranged on the cylinder tube inner shell. The outer shell cap and the inner shell cap are collectively referred to as the caps.

[0016] The cylinder tube assembly according to the invention is particularly characterized in that the calottes are designed as cold-formed concave stamping sections and form a structural hardening zone in a forming area between the calottes.

[0017] Geometrically, the calottes are shaped sections that are concave compared to the remaining surface contour of the cylinder tube outer shell and the cylinder tube inner shell, thus forming a recess and are preferably shaped like a spherical segment or oval.

[0018] The structural hardening of the structural hardening zone advantageously forms a mechanically more stable area, as the material of the cylinder tube is cold-formed there and its structure is improved by the embossing of the calottes.

[0019] In addition, the connection section has a connection hole designed for the passage of a pressure medium through the cylinder tube, either as a pressure medium inlet or outlet, depending on the operating state. According to the invention, the connection hole is designed as a punched hole and extends through the two calottes and the cylinder tube located between them. The working pressure medium can be directed into the cylinder interior via the hole.

[0020] The solution according to the invention is further characterized in particular in that the connection hole is enclosed by the structural hardening zone.

[0021] The critical area of ​​the pressure medium inlet and the pressure medium connection therefore offers greater mechanical strength.

[0022] The connecting piece is arranged on the connecting section and has a pressure medium tube. This tube is designed for a pressure medium line.

[0023] A pressure medium connection on the connecting piece, for example, designed as a threaded section, offers the possibility of connecting a pressure medium hose to the connecting piece and indirectly to the cylinder, thus supplying or discharging the pressure medium. Depending on the installation situation and operating condition, such a pressure medium hose can be deformed during dynamic cylinder movements, exerting mechanical stress on the connecting piece and indirectly on the cylinder tube in the area already inevitably weakened by the perforation. The structural strengthening here provides a more durable and highly resilient connection option.

[0024] In addition, the connection section has a connecting section which has an annular axial limiting contour that encloses the pressure medium channel.

[0025] Furthermore, the outer cap also has an annular contour, which represents an annular counter-ring surface to the annular axial boundary contour of the connecting piece.

[0026] The annular axial boundary contour according to the invention and the annular counter surface of the outer spherical cap form an annular contact surface. Advantageously, the annular contact surface is virtually gap-free. Due to the annular contact and the spherical indentation, the connection piece can be positioned with a high tolerance while still maintaining a sealed fit. Particularly with an outer spherical cap shaped like a spherical surface segment, a virtually gap-free annular contact surface is always achieved, even with a certain angular deviation of the connection piece from an ideal radius to the cylinder tube longitudinal axis.

[0027] The cylinder tube and the connecting piece are joined together at the annular contact surface by means of a ring weld. The cylinder tube and the connecting piece are collectively referred to as the joining partners. The ring weld also forms the sealing plane.

[0028] Furthermore, the pressure medium tube and the connection hole form a common pressure medium channel as a pressure medium passage through the cylinder wall.

[0029] With the cylinder tube assembly according to the invention, a solution was surprisingly found which, under the advantageous aspects described in more detail below, solves a large number of problems from the prior art in a technologically simple and reliable manner.

[0030] Advantageously, the cylinder barrel assembly according to the invention is produced using a non-cutting process, preventing chips from entering the cylinder interior and causing damage. This increases cleanliness and quality in production.

[0031] Another advantage is that burr formation at the connection hole is eliminated by the two-sided stamping. This eliminates the need for rework to remove burrs. Grinding craters that often remain after rework are also avoided. The smooth wall of the connection hole is advantageous, so that the pressure fluid flow is not disrupted and can be smooth and quiet.

[0032] In this context, there is also the advantage that the transition between the inner cylinder surface and the inner spherical cap is burr-free due to the stamping process, without the need for additional measures. This also advantageously places the connection hole to the inner spherical cap slightly radially recessed from the contour of the inner cylinder surface, so that sensitive components such as seals or guides on the piston are particularly protected during the passage.

[0033] The stamping process also provides a beneficial structural change through material compaction in the structural hardening zone, i.e., the area around the connection hole. This is particularly advantageous because the connection hole inevitably results in a structural weakening of the cylinder tube wall, which must distribute the buckling stress and the axial tensile stress around the connection hole. Depending on the application, bending forces can also be applied via the connection piece. This beneficial structural change strengthens this critical area and can thus better compensate for the structural weakening caused by the connection hole.

[0034] Furthermore, the outer calotte advantageously provides an annular counter-ring surface as a counter-surface for a flush and gap-free installation of the connecting piece, so that optimal conditions are created for a particularly high-quality and at the same time weld material-free weld connection.

[0035] Furthermore, there is the advantage that the shapes or contours of the outer spherical cap and the inner spherical cap can also differ from one another, so that special shapes such as elongated inner spherical caps for forming a damping pressure medium channel in the inner cylinder surface can be provided without additional steps.

[0036] Furthermore, it is advantageous that the connection hole, the structural hardening zone, the annular counter surface of the outer calotte and the burr-free junction of the connection hole into the cylinder inner surface are created in just one uniform operation, thus enabling cost-effective and effective production.

[0037] The punching of the connecting hole creates a plug, also called a slug, which can advantageously be fully recycled as clean core scrap. Furthermore, the energy consumption during production for the punching and stamping process according to the invention is significantly lower than for the multi-stage machining processes of the state of the art. Furthermore, there are no contaminated chips that would be costly to dispose of.

[0038] According to an advantageous further development, the cylinder tube assembly is characterized in that the cylinder tube assembly is designed as part of a working cylinder.

[0039] This development particularly preferably involves a cylinder assembly of a hydraulic working cylinder. This cylinder is subjected to particularly high loads, so that the described advantages of high quality and strength are particularly effective. Such a working cylinder comprises the cylinder tube assembly and a piston unit and is used as a linear pressure flow consumer in many applications.

[0040] According to another advantageous development, the cylinder tube assembly is characterized in that the ring weld seam is designed as a pressure weld seam.

[0041] The pressure weld offers the advantage that the structure in the area surrounding the weld is changed less than with other welding processes, especially since the heat input into the material of the welding partners is extremely low.

[0042] The advantageous further development as a pressure weld seam is possible because the solution according to the invention creates a practically gap-free contact surface by providing the annular counter surface of the outer calotte to the annular axial boundary contour of the connecting piece.

[0043] According to a further advantageous development, the cylinder tube assembly is characterized in that the ring weld seam is formed without any welding material. Advantageously, no additional material is required for welding.

[0044] The welding can thus be carried out advantageously with lower energy input, with greater technological simplicity and speed, and without the occurrence of weld spatter. Furthermore, there is no material mixing with an added weld metal at the weld point, which could lead to increased corrosion or structural distortion.

[0045] According to a next advantageous development, the cylinder tube assembly is characterized in that the outer shell cap is designed as a spherical surface section.

[0046] Due to the spherical shape, the structural transition along the cylinder tube wall toward the connection hole, which forms part of the pressure fluid channel, is gradual, preventing structural jumps. This prevents crack formation or dynamic fractures.

[0047] Furthermore, the shape of the outer spherical cap as a spherical surface section offers the advantage that a circular line can be geometrically inscribed on the outer spherical cap surface. Furthermore, the plane of this circular line can be arranged at different angles, making it particularly easy to align the connection piece and always achieving a gap-free annular contact surface.

[0048] According to another advantageous development, the cylinder barrel assembly is characterized in that the inner jacket cap is designed as a damping pressure medium channel.

[0049] This further development relates to damping solutions in which the piston has a piston ring and the connection hole in the cylinder end area is offset axially proximally, so that the piston, when approaching the end position, passes over the connection hole with its piston ring and thus encloses a pressure medium volume in the cylinder end area.

[0050] When the piston passes over the inner skirt cap with its piston ring, the pressure medium channel is not completely closed by the piston. Rather, a small amount of pressure medium can flow past the piston ring in the inner cap formed in this way. This can dampen the piston movement. The cross-section of the damping pressure medium channel determines the degree of damping, and its axial extent determines the damping travel. In a special design, progressive damping can also be achieved by having a cross-section that varies along its axial extent.

[0051] According to a further aspect of the invention, the cylinder tube assembly is obtained by a manufacturing method described in more detail below.

[0052] The method for producing a cylinder tube assembly is characterized in that the cylinder tube assembly is designed according to one of claims 1 to 6 and has the following method steps: a) Preparing the cylinder tube

[0053] The starting point of the process is a cylinder tube, which is obtained from a bar material by cutting to length, turning and, if necessary, further processing steps.

[0054] The cylinder tube thus prepared is inserted into a fixture. The fixture consists of a press capable of performing a lifting movement and a tool with a defined holder for the tube. This ensures that, in series production, the tubes are always inserted in the same position, and the machining always takes place at the same point on the tube. b) Punching of the connection holes and forming of the calottes by cold forming using a punching-forming punch and a counter punch

[0055] The cutting die preferably has a spherical cutout-shaped embossing contour and a cylindrical cutting pin that penetrates the center of the spherical cutout. The die also protrudes from the spherical cutout by at least the length of the single wall thickness of the cylinder tube.

[0056] In the punching phase of process step b), the cutting punch contour penetrates into the cylinder tube and punches the connection hole as a cylindrical opening.

[0057] After the punch continues its movement, the preferably spherical area imprints the outer spherical cap into the cylinder tube exterior during the stamping phase. The counter punch provides the counter force. To do this, it takes up the inner shape of the cylinder tube. The counter punch also has a preferably spherical, convex contour and thus creates the inner spherical cap at the same time as the outer spherical cap. Furthermore, the counter punch is interspersed with a cylindrical opening into which the punched cylinder slug and the cutting punch section are inserted.

[0058] During the stamping phase, the cutting punch, still located in the connecting hole, advantageously supports the inner walls of the connecting hole, so that the cylinder tube material, which plastically forms in the microstructure compaction zone during stamping, is particularly compacted on the inner walls. At the same time, the opening cross-section of the connecting hole is protected from deformation.

[0059] In addition, it is possible to carry out a further stamping step with a different stamping tool after process step b) in order to remove any burr in the connection hole or to further shape the domes.

[0060] According to a further aspect of the invention, method step b) can also be carried out in two stages. In a first stage, the connection holes are punched using a punching die, and in a second stage, the caps are embossed using an embossing die, which simultaneously presses in and thus eliminates any punching burrs.

[0061] In an advantageous variant, method step b) can also be carried out for both pressure medium connections at the same time for a cylinder tube that is to have two lateral pressure medium connections - one pressure medium connection in each end region - so that after this method step a cylinder tube is provided with the connection section at one end region and a further connection section at the other end region. For this purpose, in this development the press has, in addition to the cutting die punch and the counter punch, a further cutting die punch and a further counter punch. The two counter punches are positioned on both sides in the cylinder tube interior where the respective connection section is to be created. Both cutting die punches can then be actuated in one press stroke. This particularly applies to cylinder tube assemblies for double-acting working cylinders such as differential cylinders or double-action cylinders. c) Positioning the connecting piece on the outer calotte and establishing a fixed positional relationship while forming the annular contact surface and obtaining a pre-assembly

[0062] The connecting piece is placed in the area of ​​the outer spherical cap with its annular contact surface. Due to the combination of the shape of the outer spherical cap and the annular contact surface of the connecting piece, a high angular tolerance is advantageous during positioning and placement. This always creates a completely gap-free contact between the joining geometries, resulting in a homogeneous, material-tight connection after the next process step. d) Welding of the cylinder tube and the connecting piece to produce the ring weld

[0063] Particularly preferably, the welding is carried out by producing a resistance pressure weld with pressure on the joining partners.

[0064] Welding ensures a firm and materially bonded connection between the cylinder tube and the connecting piece. The connection is also pressure-tight. Due to the gap-free pre-positioning of the joining geometries, welding can be performed to a high standard of quality without the need for costly post-processing.

[0065] A pressure fluid supply in the form of a hose or pipe can now be mounted on the cylinder barrel. The connection between the connecting piece and the cylinder barrel also provides sufficient resistance to dynamic loading resulting from hose movement due to pressure surges or cylinder movement.

[0066] Like process step b), the two process steps c) or d) can optionally be carried out simultaneously for two connection sections.

[0067] In an advantageous further development, the method for producing a cylinder tube assembly is characterized in that in method step b) the punching and forming is carried out by means of a counter punch designed as a hardened ball.

[0068] The counter punch therefore also has a convex, spherical section. This is embossed into the inside of the cylinder tube, forming a concave dome.

[0069] By designing the counter punch with a hardened ball, a cost-effective stamping tool with high process stability can be provided.

[0070] According to another advantageous development, the method for producing a cylinder tube assembly is characterized in that in method step d) the welding is carried out as resistance pressure welding.

[0071] Due to the continuous, gap-free annular support of the connecting piece on the outer shell dome, the applied energy is evenly distributed. This results in a precise and fluid-tight weld seam without the need for additional material.

[0072] The invention is illustrated by way of example with reference to Fig. 1 schematic oblique view of a cylinder tube assembly Fig. 2 schematic oblique view of the cylinder tube Fig. 3 schematic sectional view along the cylinder tube axis Fig. 4 schematic sectional view perpendicular to the cylinder tube axis Fig. 5 schematic sectional view of the punching and embossing tool explained in more detail.

[0073] Identical reference symbols in the various figures refer to identical features or components. These reference symbols are used in the description even if they are not shown in the respective figure.

[0074] The Fig. 1 shows a schematic oblique view of the entire cylinder tube assembly. The cylinder tube 1 is in Fig. 1 connected to the connecting piece 2. The connecting piece 2 is integrally connected in the area of ​​the outer cap 3 by means of the ring weld 8.

[0075] The Fig. 2 shows a schematic oblique view of the cylinder tube 1 prepared for joining. Here, a spherical segment-shaped outer cap 3 is stamped onto the cylinder tube's outer surface. The connection hole 5 is also punched for the pressure medium flow.

[0076] The Fig. 3 shows the entire cylinder tube assembly in a sectional view, cut along the cylinder tube longitudinal axis.

[0077] In the area of ​​the connecting section 1.3, a spherical segment-shaped outer spherical cap 3 is embossed into the cylinder tube outer shell 1.1 of the cylinder tube. Opposite, on the cylinder tube inner shell 1.2, the inner spherical cap 4, also with a spherical segment-shaped contour, is embossed into the cylinder tube 1. Depending on the penetration depth, the structure of the cylinder tube material is densified by a defined amount. This results in local hardening of the material. This is the microstructure hardening zone 1.4.

[0078] At the same time, a connection hole 5 is punched, which provides the pressure medium flow.

[0079] The connecting piece 2 has the pressure medium tube 6 for the pressure medium passage. Furthermore, the connecting piece 2 has the connecting section 7 with an annular end contour. This is the annular axial limiting contour 7.1. Opposite this limiting contour 7.1 in a joining position is the annular counter-ring surface 3.1 of the outer spherical cap 3.

[0080] The connecting piece is placed on the outer shell cap 3 and connected by pressure welding via the ring weld 8, which also forms the sealing plane for the pressure medium. The pressure medium can then flow via the connecting piece 2 through the connection hole 5 into the interior of the cylinder tube 1 and vice versa.

[0081] The Fig. 4 shows the cylinder tube assembly in a sectional view, cut transversely to the cylinder tube longitudinal axis.

[0082] In combination with Fig. 3 are in Fig. 4 In particular, the spherical segment-shaped contours of the outer shell cap 3 and the inner shell cap 4 are depicted. When joining the cylinder tube 1 to the connecting piece 2 in process step c), the annular axial boundary contour 7.1 of the connecting piece 2 and the annular counter-ring surface 3.1, as a surface section of the spherical segment-shaped concave surface of the outer shell cap 3, lie opposite one another without a gap. Even if the joining partners 1, 2 are tilted relative to one another with a large angular deviation, the shape of the outer shell cap 3 ensures a gap-free and sealing contact after welding.

[0083] During the subsequent pressure welding in process step d), a uniform energy input and, as a result, a pressure-tight, material-tight connection is achieved by means of the ring weld 8. The pressure fluid can flow smoothly into the interior of the cylinder tube 1 via the connection hole 5 and the adjoining inner shell spherical cap 4.

[0084] The Fig. 5 shows in a schematic sectional view the punching and stamping tool for the process for machining the connecting section 1.3 of the cylinder tube 1 for the subsequent joining of the connecting piece 2.

[0085] Here, the cylinder tube 1 prepared in process step a) is positioned on a counter-punch 9.2. The punching-forming punch is fed from the outside of the cylinder tube 1 in process step b). The punching-forming punch 9.1 consists of a cylindrical punching section arranged on a spherical segment-shaped stamping section. Consequently, the connecting hole 5 can be punched into the cylinder tube 1 with the punching-forming punch 9.1, and the outer shell cap 3 and the inner shell cap 4 are simultaneously stamped with the same press stroke.

[0086] In the present embodiment, the counter punch 9.2 also has a spherical segment-shaped stamping contour. This allows the inner shell cap 4 to be stamped in the same work step. In addition, the counter punch 9.2 has a conical bore in the center that accommodates the punch slug and the cylindrical forming section of the punch-forming punch 7. Using this tool design, the entire required joining contour on the cylinder tube 1 can be produced with just one press stroke. Reference symbols used

[0087] 1Cylinder tube 1.1Cylinder tube outer shell 1.2Cylinder inner shell 1.3Connection section 1.4Structure hardening zone 2Connection nozzle 3Outer shell cap 3.1Annular counter surface 4Inner shell cap 5Connection hole 6Pressure medium tube 7Connection section 7.1Annular axial boundary contour 8Annular weld seam 9.1Punching-forming punch 9.2Counter punch

Claims

1. A cylinder tube assembly group, comprising a cylinder tube (1) and a connection piece (2), wherein the cylinder tube (1) comprises a cylinder basic body and a connection portion (1.3), wherein the connection portion (1.3) has an outer shell calotte (3), an inner shell calotte (4), a structural strengthening zone and a connecting borehole (5), wherein the outer shell calotte (3) is arranged on a cylinder outer shell (1.1) and the inner shell calotte (4) is arranged on a cylinder inner shell (1.2), and wherein the calottes (3, 4) are formed as cold-formed concave embossing-form portions, wherein the structural strengthening zone (1.4) is arranged in a forming region between the calottes (3, 4), wherein the connecting borehole (5) is designed for a pressure medium passage of a pressure medium and as a punched borehole and passes through the calottes (3, 4), and wherein the structural strengthening zone encompasses the connecting borehole (5), wherein the connection piece (2) is arranged at the connection portion (1.3) and comprises a pressure-medium tube (6) and a connection section, wherein the pressure-medium tube (6) is designed for a pressure-medium line of the pressure medium, wherein the connection section has an annular axial boundary contour (7.1), wherein the annular axial boundary contour (7.1) and an annular mating surface (3.1) of the outer shell calotte (3) form an annular contact surface, wherein the cylinder tube (1) and the connection piece (2) are connected in a positive substance manner at the annular contact surface by means of a ring weld seam (8) and the ring weld seam (8) forms a sealing plane, and wherein the pressure medium tube (6) and the connecting borehole (5) form a common pressure medium channel.

2. The cylinder tube assembly group according to claim 1, characterized in that the cylinder assembly group is designed as a part of a working cylinder.

3. The cylinder tube assembly group according to one of the preceding claims, characterized in that the ring weld seam is designed as a press weld seam.

4. The cylinder tube assembly group according to one of the preceding claims, characterized in that the ring weld seam is produced free of welding material.

5. The cylinder tube assembly group according to one of the preceding claims, characterized in that the outer shell calotte (3) is designed as a spheric surface portion.

6. The cylinder tube assembly group according to one of the preceding claims, characterized in that the inner shell calotte (4) is designed as a damping pressure medium channel.

7. A method for producing a cylinder tube assembly group, characterized in that the cylinder tube assembly group is designed according to one of the claims 1 to 6 and that it comprises the following process steps: a) providing the cylinder tube (1), b) punching the connecting borehole (5) and forming the calottes by cold forming using a punch-and-die stamp (7) and a counter stamp (8), c) positioning the connection piece (2) at the outer calotte (3) and establishing a fixed positional relationship while forming the annular contact surface and obtaining a pre-assembly group, d) welding the cylinder tube (1) and the connection piece (2) by producing the ring weld seam.

8. The method for producing a cylinder tube assembly group according to claim 7, characterized in that in process step b) punching and forming is carried out by means of a counter stamp (8) in the design of a hardened ball.

9. The method for producing a cylinder tube assembly group according to claim 7 or 8, characterized in that in process step d) welding is performed as a resistance-pressure welding process.