阅读说明：本技术 活塞和活塞杆组件的制造方法 (Method for producing piston and piston rod assembly ) 是由 马塞尔·格拉尔杜斯·玛丽亚·尼乌文赫伊斯 于 2019-01-28 设计创作，主要内容包括：用于线性致动器的活塞和活塞杆组件通过摩擦焊接方法制造。活塞杆包括由狭窄部分形成的闪光部分,该闪光部分具有由端面形成的闪光表面。活塞包括由中心定位的凹陷形成的闪光腔室。在摩擦焊接方法中,将闪光部分插入到闪光腔室中,并在活塞杆与活塞之间实施相对旋转和轴向压力,使得闪光表面接合到腔室底部。有利地,提供清洁焊接步骤,该步骤允许围绕活塞杆预先放置密封组件。在执行清洁焊接步骤之前,包括擦拭器、密封圈和密封压盖的密封组件可以围绕活塞杆放置。(The piston and piston rod assembly for a linear actuator is manufactured by a friction welding method. The piston rod includes a flash portion formed by a narrowed portion, the flash portion having a flash surface formed by an end face. The piston includes a flash chamber formed by a centrally located recess. In the friction welding method, a flash portion is inserted into a flash chamber, and relative rotation and axial pressure are applied between a piston rod and a piston so that a flash surface is bonded to the bottom of the chamber. Advantageously, a clean welding step is provided which allows for the pre-placement of the sealing assembly around the piston rod. A seal assembly including a wiper, a seal ring, and a seal gland may be placed around the piston rod prior to performing the clean weld step.)

1. Method for manufacturing a piston and piston rod assembly (20), wherein the method comprises the step of connecting the piston to the piston rod, wherein:

the piston rod is an elongated piston rod (30) defining an axial axis, and the piston rod (30) has a proximal rod end (31) and a distal rod end (32), wherein the piston rod (30) comprises a flash portion (39) formed by a narrow portion at the proximal rod end (31) and a flash surface (390) formed by an end face at the proximal rod end (31) of the piston rod (30); and wherein:

the piston (50) comprises a flash chamber (52), the flash chamber (52) being formed by a centrally located recess in an end face (51) of the piston (50), wherein the recess has a recess bottom forming a chamber bottom (520) and a recess inner circumferential wall forming a chamber wall (521);

wherein the method comprises at least the steps of:

inserting the flash portion (39) of the piston rod (30) into the flash chamber (52) of the piston (50) such that the flash surface (390) contacts the chamber bottom (520); and

friction welding the piston rod (30) to the piston (50) by causing relative rotation and axial pressure between the flash surface (390) of the piston rod (30) and the chamber bottom (520) of the piston (50) such that the flash surface (390) engages the chamber bottom (520).

2. The method of claim 1, wherein the method further comprises the preceding steps of:

securing a club head (40) to the distal rod end (32) of the piston rod (30); and

placing at least one sealing assembly (60), in particular a subassembly consisting of a wiper (63), a sealing ring (62) and a sealing gland (61), around the piston rod (30),

wherein after the previous step the following steps are performed consecutively:

inserting the flash portion (39) into the flash chamber (52) such that the flash surface (390) contacts the chamber bottom (520); and

friction welding the piston rod (30) to the piston (50) by applying relative rotational and axial pressure between the piston rod (30) and the piston (50) such that the flash surface (390) engages the chamber bottom (520).

3. The method of claim 2, wherein in the friction welding step, the piston (50) is rotated relative to the piston rod (30) while the piston rod (30) remains stationary.

4. A method according to claim 2 or 3, wherein the rod head (40) is fixed to the distal rod end (32) by welding, in particular by friction welding.

5. The method according to any one of the preceding claims, wherein the piston rod (30) comprises a centering portion (37) positioned beside the flash portion (39) for centering the piston (50) relative to the piston rod (30).

6. A piston and piston rod assembly (20) for a linear actuator (10), wherein the piston is connected to the piston rod by friction welding, wherein the piston and piston rod assembly comprises:

a piston (50) for subdividing the inner space of a cylinder housing (11) of the linear actuator (10) into a pulling chamber (12) and a pushing chamber (13), wherein the piston (50) comprises a flash chamber (52) formed by a centrally located depression at an end face (51) of the piston (50), wherein the depression has a depressed bottom forming a chamber bottom (520) and a depressed inner circumferential wall forming a chamber wall (521); and

an elongated piston rod (30) having a proximal rod end (31) and a distal rod end (32), wherein said piston rod (30) comprises a flash portion (39) at said proximal rod end (31), the flash portion (39) being formed by a narrow portion, and the flash portion (39) having a flash surface (390) formed by an end face of said piston rod (30),

wherein the flash chamber (52) is adapted to receive the flash portion (39) of the piston rod (30) such that the flash surface (390) abuts the chamber bottom (520).

7. The piston and piston rod assembly (20) of claim 6, wherein the flash portion (39) has a flash portion length (fpl), and wherein the flash chamber (52) has a flash chamber depth (chd), the flash portion length being at most 2 millimeters greater than the chamber depth.

8. The piston and piston rod assembly (20) according to claim 6 or 7, wherein the piston rod (30) comprises a centering portion (37) for centering the piston (50) relative to the piston rod (30), wherein the centering portion (37) is located beside the flash portion (39), in particular adjacent to the flash portion (39).

9. The piston and piston rod assembly (20) of any one of claims 6-8, wherein the piston (50) is made of a steel material.

10. The piston and piston rod assembly (20) of any one of claims 6-9, further comprising:

a rod head (40) welded to said distal rod end (32) of said piston rod (30) adapted to mount said piston and piston rod assembly (20) to an operable component;

a seal assembly (60) slidably mounted about the piston rod (30).

11. Linear actuator (10), in particular hydraulic linear actuator, wherein the linear actuator (10) comprises a cylinder housing (11) and a piston and piston rod assembly (20) according to any one of claims 6-10.

12. Cab tilting system (4) comprising a tilting cylinder (5) formed by a hydraulic linear actuator according to claim 11, further comprising an assembly of a pump (16), a reservoir (17) and a control valve (15), said assembly being adapted to operate the tilting cylinder (5) to raise the cab of the vehicle (1) relative to the chassis (3).

13. Vehicle (1) comprising a cab tilting system (4) according to claim 12.

Technical Field

The invention relates to a method for manufacturing a piston and piston rod assembly, a linear actuator, a cab tilting system and a vehicle.

Background

EP2,949,417 discloses a method of manufacturing a piston and piston rod assembly by joining end faces of a piston rod and a rod head to each other by friction welding. The piston rod has a distal rod end adapted to be connected to a rod head. Both the piston rod and the rod head have flat annular end surfaces. A hollow portion is provided at the end face to reduce the joint area (compared with the case where the end face is not recessed). Due to the hollow portion, the size of the apparatus for friction welding can be reduced. The friction welding causes the base material of the end face to be discharged to the outer and inner peripheral sides of the joining region. Plastic flow of the base material occurs during friction welding, and eventually the outer and inner circumferential weld beads remain in the joint area. The outer bead can be removed from the outer peripheral side by a continuous cutting operation. The inner bead on the inner peripheral side is closed and held. The piston rod has a large diameter portion over its length. At the proximal rod end, the piston rod has a small diameter portion to which the annular piston is to be connected. The step portion is provided on a boundary between the small diameter portion and the large diameter portion. The piston may be anchored on the step portion by a nut fastened to the external threaded portion of the small diameter portion.

US3,596,570 discloses a hydraulic actuator which is fully assembled by a plurality of friction welds. This configuration allows for the elimination of many components that were previously necessary in such actuators, reduces the likelihood of fluid leakage, and reduces the overall length of the actuator as compared to other actuators having the same stroke length. The piston rod is welded directly to the piston head. The piston head has an end face provided with a groove or counterbore for receiving the end of the piston rod. The grooves form flash traps to prevent flash material from the weld from protruding beyond the end face of the piston head.

US2016/159377 discloses a brake piston assembly. The brake cylinder piston assembly has a composite piston head with a bore formed therethrough, a cup located in the bore and coupled to the piston head, and a hollow rod fixedly welded to the cup. The cup may be coupled to the hollow stem by friction welding to provide a secure water-tight assembly. The piston assembly is assembled by aligning the bore of the piston head with the outer diameter of the cup and then pressing the two elements axially together until the shoulder of the bore of the piston head engages the shoulder of the cup and the locking fingers engage the rim of the cup so that the locking tabs on the ends of the fingers firmly grip the rim of the cup.

It is known to manufacture a piston and piston rod assembly for a linear actuator by first welding the rod head to the piston rod and then mounting the piston to the piston rod. In one manufacturing step, the seal assembly is placed around the large diameter portion prior to mounting the piston to the piston rod. A sealing assembly is arranged for sealing the piston and piston rod assembly with respect to the cylinder housing of the linear actuator. The reason for welding the rod head first, then placing the seal assembly, and finally installing the piston is to prevent contamination or damage to the seal assembly or the piston during the manufacturing process. The head is welded and then subjected to a finishing operation, such as cutting, to remove the outer bead resulting in particle release. In order to prevent contamination or damage of the seal assembly or the piston by these particles, such welding operations following the finishing operation always need to be carried out first. Since the sealing assembly has to be placed between the rod head and the piston, it is not possible to weld the piston to the piston rod also in a clean manner.

Disclosure of Invention

It is a general object of the present invention to at least partly obviate the above disadvantages and/or to provide a usable alternative. More specifically, it is an object of the present invention to provide a method for manufacturing a piston and piston rod assembly, wherein both the rod head and the piston can be welded to the piston rod. More specifically, it is an object of the present invention to provide a piston and piston rod assembly and a method for manufacturing such a piston and piston rod assembly, wherein both the rod head and the piston are welded to the piston rod.

According to the invention, this object is achieved by a method for manufacturing a piston and piston rod assembly according to claim 1.

The piston and piston rod assembly is manufactured as a subassembly for assembling a linear actuator, in particular a hydrodynamic linear actuator, more particularly a hydraulic cylinder actuator. By implementing the method, the piston is connected to a piston rod.

The method comprises the step of connecting the piston to a piston rod.

The piston rod is an elongated piston rod. The elongate piston rod defines an axial axis. The piston rod has a proximal rod end and a distal rod end. The proximal rod end may also be referred to as an inner rod end because the proximal rod end will be placed within the housing of the linear actuator. The distal rod end may also be referred to as an outer rod end because the distal rod end is located outside of the housing of the linear actuator.

The piston rod includes a flash portion formed by a narrow portion at the proximal rod end. The piston rod includes a flash surface formed by an end surface at a proximal rod end of the piston rod.

The piston comprises a flash chamber formed by a centrally located recess in the end face of the piston. The recess has a recess bottom forming a chamber bottom and a recess inner peripheral wall forming a chamber wall.

The method according to the invention comprises at least the steps of inserting the flash portion into the flash chamber such that the flash surface contacts the bottom of the chamber, and friction welding the piston rod to the piston by causing relative rotation and axial pressure between the flash surface of the piston rod and the bottom of the chamber of the piston such that the flash surface engages the bottom of the chamber.

Advantageously, the method according to the invention comprises a clean welding step provided by the friction welding step, which allows to pre-position the sealing assembly around the piston rod. A seal assembly including a wiper, a seal ring, and a seal gland may be placed around the piston rod prior to performing the clean weld step.

A bonding region is formed between a flash surface within the flash chamber and the bottom of the chamber. During friction welding, the base material is flowing and a bead is formed around the flash portion of the chamber bottom. The chamber walls surround the joining region and surround the formed weld bead. Therefore, the weld bead is shielded from the outside by the chamber wall. The joining region and the weld bead are positioned in a protected form in a substantially inaccessible manner from the outside. Mechanical shock or other external influences hardly damage the welded joints in the flash chamber.

Advantageously, the method according to the invention allows to manufacture piston and piston rod assemblies, wherein the proximal and distal rod ends are welded to the piston and rod head, respectively. The rod head may be first welded to the piston rod by friction welding or by another welding method (e.g., where a weld material is added). If necessary, cutting, etching and/or cleaning operations may then be performed to remove any welding residues from the club head. Subsequently, the seal assembly is placed around the piston rod, after which the piston is welded by friction welding in the manner described above to secure the piston to the piston rod. Since the welding of the rod head and, if necessary, the post-welding operation steps are performed before the placement of the seal assembly, and since the welding of the piston to the piston rod is a clean welding step, damage or contamination to the assembled piston and piston rod can be greatly reduced. The seal assembly may remain clean and intact during the friction welding step used to secure the piston. Performing the friction welding step according to the invention after placing the sealing assembly to fix the piston to the piston rod may advantageously prevent any degradation of the sealing assembly.

In one embodiment of the method according to the invention, the method comprises the steps of, before performing the step of inserting the flash portion into the flash chamber, fixing the rod head to the distal rod end of the piston rod and placing at least one sealing assembly, in particular a subassembly consisting of a wiper, a sealing ring and a sealing gland, around the piston rod, such that the flash surface contacts the bottom of the chamber, and friction welding the piston rod to the piston by applying a relative rotational and axial pressure between the piston rod and the piston such that the flash surface engages the bottom of the chamber.

Preferably, the rod head is fixed to the distal rod end of the piston rod by welding, in particular by friction welding. After the club head is secured to the distal club end and before the seal assembly is placed, process residues may be removed or another post-connection step may be performed. Thus, the sequence of steps of the method may prevent any contamination or damage to the assembled piston and piston rod assembly.

It is worth noting that in this embodiment of the method according to the invention, instead of the rod head (as seen in the prior art provided in EP2,949,417), the piston is welded to the piston rod by a friction welding step. A flash chamber on the piston receives the flash portion of the piston rod so that the engagement area and the weld bead are in a position protected by the chamber wall. In one embodiment, a gap may be maintained between the piston and the piston rod, and thus the engagement region and the weld bead may remain exposed to the environment surrounding the piston. In the assembled linear actuator, the piston is located within the cylinder housing. The cylinder housing provides a protected environment. In particular, the piston is located in a hydraulic fluid environment that provides a corrosion-resistant protective environment. Thus, the piston is located in an environment that is less or not susceptible to corrosion at all, as opposed to the club head. In view of this, friction welding, which does not have any continuous operation steps that could damage or contaminate the placed sealing element, provides a weld joint between the piston and the piston rod, rather than between the rod head and the piston rod. Since the piston is located in a protected environment, it is not problematic that the welded joint may be exposed to its surroundings.

In a further embodiment of the method according to the invention, the piston is rotated relative to the piston rod during the friction welding step, while the piston rod remains fixed. The seal assembly is placed around the piston rod and remains stationary during the friction welding step since the piston rod does not rotate. Advantageously, holding the seal assembly stationary may prevent damage to the seal assembly.

In an embodiment of the method according to the invention, the head is fixed to the distal rod end by welding, in particular by friction welding. Advantageously, an assembly consisting of a piston and a piston rod is obtained, which comprises a welded rod head and a welded piston. The welded connection on both sides of the piston and piston rod assembly may contribute to the mechanical strength of the piston rod. Advantageously, the piston and piston rod assembly may be adapted for use in heavy duty environments. A heavy duty hydraulic cylinder may include a piston and piston rod assembly according to the present invention.

In an embodiment of the method according to the invention, the piston rod comprises a centering portion beside the flash portion. The centering portion serves to center the piston relative to the piston rod. Advantageously, the centering portion contributes to the accuracy of the alignment of the piston and the piston rod. Furthermore, the centering portion may be received in the flash chamber and may close the flash chamber in the axial direction.

Furthermore, the invention relates to a piston and piston rod assembly for a linear actuator. The piston and piston rod assembly is an assembly in which the piston is connected to a piston rod. By another notation, a "piston and piston rod assembly" may be denoted as a "piston/piston rod assembly" or a "piston-piston rod assembly," which is synonymous.

According to the present invention, a piston and piston rod assembly for a linear actuator is provided, wherein the piston is connected to the piston rod by friction welding.

The piston and piston rod assembly comprises a piston for subdividing the inner space of the cylinder housing of the linear actuator into a pull chamber and a push chamber. The piston includes a flash chamber formed by a recess centrally located in the end face of the piston.

The recess has a recess bottom forming a chamber bottom and a recess inner peripheral wall forming a chamber wall.

The piston and piston rod assembly further includes an elongate piston rod having a proximal rod end and a distal rod end. Preferably, the piston rod is solid, wherein the piston rod is a massive shaft. The plunger rod includes a flash portion at the proximal rod end. The flash portion is formed of a narrow portion. The diameter of the flash portion is smaller than the main diameter of the piston rod. Preferably, the main diameter of the piston rod is an outer diameter of at most 20 mm, which increases the stability of the method. The flash portion has a flash surface formed by an end surface of the piston rod. Preferably, the flashing portion has a smooth outer peripheral surface.

The flash chamber is adapted to receive the flash portion of the piston rod such that the flash surface abuts the chamber bottom.

Such a piston and piston rod assembly is a product obtainable by the method according to the invention.

An engagement area is provided at the chamfered bottom of the piston. The joint area is surrounded by a chamfered wall so that the joint area is isolated from the outside. The bursts of material flow during the friction welding process may be located at the outer periphery of the flash portion being welded and laterally separated from the exterior by a chamfered wall.

A gap may exist and form between the end surface of the piston and the annular end surface of the piston rod, seen in the axial direction. This gap provides an open communication to the outside. However, in the assembled linear actuator, the piston will be located within the cylinder housing providing a protected environment. In particular, the piston is surrounded by hydraulic liquid, thereby further protecting the joint area from corrosion. Unlike the piston, the rod head is located outside the cylinder housing, in a more corrosive environment. For this reason, the welded joint obtained by friction welding, which is subjected to the cleaning process but opened, is performed on the piston, not on the head.

In one embodiment of a piston and piston rod assembly according to the present invention, the flash portion has a flash portion length "fpl" and the flash chamber has a flash chamber depth "chd", wherein the flash portion length is at most 2 millimeters greater than the chamber depth.

Advantageously, the clearance between the end face of the piston and the annular end face between the first part and the remaining part of the piston rod is limited to at most 2 mm, preferably at most 1 mm, which helps to reduce possible contamination from the flash chamber. The bursts in the friction welding step are surrounded by the flash chamber and are resisted by the gap.

In an embodiment of the piston and piston rod assembly according to the invention, the piston rod comprises a centering portion for centering the piston relative to the piston rod. The centering portion is located beside the flash portion. In particular, the centering portion is positioned adjacent to the flash portion. The outer diameter of the centering portion is larger than the outer diameter of the flash portion but smaller than the main diameter of the piston rod. The centering portion contributes to the coaxiality of the piston with respect to the piston rod. Furthermore, the centering portion may close the flash chamber, which may eliminate the escape of welding residues during the friction welding step.

In one embodiment of the piston and piston rod assembly according to the invention, the piston is made of a steel material. Preferably, both the piston rod and the piston are made of a steel material. Advantageously, the steel material may facilitate a suitable welding process. Furthermore, such a piston and piston rod assembly made of steel may comply with the specifications as specified for heavy duty environments (like e.g. in cab tilting systems) where heavy loads are to be handled.

In one embodiment of the piston and piston rod assembly according to the invention, the piston and piston rod assembly further comprises a rod head welded to the distal rod end of the piston rod. The rod head is adapted to mount the piston and piston rod assembly to an operable member, such as the cab of a truck. Further, the piston and piston rod assembly includes a seal assembly slidably mounted about the piston rod.

Furthermore, the present invention relates to a linear actuator, in particular a hydraulic linear actuator. The linear actuator comprises a cylinder housing comprising an inner space and a piston and piston rod assembly according to the invention as described above.

Furthermore, the invention relates to a cab tilting system comprising a tilting cylinder formed by a hydraulic linear actuator according to the invention. Cab tilting systems are known in the prior art. Such a cab tilting system comprises an assembly of a pump, a reservoir and a control valve, which assembly is adapted to operate a tilting cylinder to raise the cab of the vehicle relative to the chassis.

Furthermore, the invention relates to a vehicle, in particular a truck, comprising a cab tilting system according to the invention.

Drawings

The invention will be explained in more detail with reference to the drawings. The drawings illustrate practical embodiments according to the invention and are not to be construed as limiting the scope of the invention. Certain features may also be considered as different from the embodiments shown, and may be considered as delimiting features in a broader context, not only for the embodiments shown, but also as common features for all embodiments falling within the scope of the appended claims, wherein:

figure 1 shows a linear actuator according to the invention in a cross-sectional view;

FIG. 2 illustrates in more detail the piston and piston rod assembly of the linear actuator shown in FIG. 1;

FIGS. 3A and 3B illustrate successive steps of a method of manufacturing a piston and piston rod assembly, wherein a rod end is friction welded to a piston;

FIG. 3C illustrates an enlarged view of a friction welded piston and piston rod assembly, wherein the rod end includes a centering portion;

fig. 4 shows in a schematic view a vehicle comprising a cab tilting system according to the invention, which comprises a linear actuator, a tilting cylinder;

fig. 5 shows a hydraulic scheme of the tilting system of fig. 4.

The same reference numbers will be used throughout the drawings to refer to the same or functionally similar parts.

Detailed Description

Fig. 1 shows a schematic cross-sectional view of a linear actuator 10 according to the invention. The linear actuator 10 is embodied here as a hydraulic actuator, in particular as a hydraulic double-acting actuator.

The linear actuator 10 has a cylinder housing 11 including a cylinder block 110 and a cylinder base 111. A cylinder base 111 is located at the proximal end of the cylinder block 110 and is adapted to mount the linear actuator in a fixed position. The cylinder base 111 includes an eye connection 112 for pivotally mounting the linear actuator 10. Eye connection 112 is welded to cylinder block 110.

The cylinder block 110 defines an inner space. The inner space is subdivided into a pulling chamber 12 and a pushing chamber 13. The pulling chamber 12 and the pushing chamber 13 are defined by a movable piston 50. The piston 50 is connected to the piston rod 30. The piston rod 30 is elongate and defines an axial axis a-a. The piston rod 30 is a solid shaft. The piston rod 30 is massive. The piston rod 30 has a proximal rod end 31 and a distal rod end 32. The piston 50 is connected to the proximal rod end 31 of the piston rod 30. Rod head 40 is connected to distal rod end 32 of piston rod 30. Here, the club head 40 includes an eye connection 44 for pivotally mounting the linear actuator 10 to an operable component. The eye connector 44 is welded to the distal rod end 32. Referring to fig. 4 and 5, the welded connection of the cylinder base 111 and the rod head 40 makes the linear actuator suitable for use in heavy-duty environments, such as in a vehicle's tilt system.

Furthermore, the linear actuator comprises a sealing assembly 60 for sealing the cylinder housing 11 with respect to the piston rod 30. The seal assembly 60 is positioned distal to the cylinder 110. A seal assembly 60 surrounds the piston rod 30. Typically, the seal assembly 60 comprises a subassembly of a seal gland 61, a seal ring 62 and a wiper 63.

According to the invention, the piston 50 is welded to the piston rod 30 by friction welding. The welded assembly of the piston 50 and the piston rod 30 forms a piston and piston rod assembly 20, which is further illustrated in FIG. 2. The piston 50 is welded to the proximal rod end 31 of the piston rod 30 by friction welding. A seal assembly 60 is slidably mounted along the piston rod 30. Rod head 40 is connected to distal rod end 32 of piston rod 30. The rod head 40 may be screwed to the piston rod 30, but preferably the rod head 40 is welded to the piston rod 30, in particular by friction welding.

In a preferred embodiment of a method for manufacturing a piston and piston rod assembly 20 according to the invention, a first step is performed to weld the rod head 42 to the distal rod end 32 of the piston rod 30. Subsequently, if necessary, a step of removing any weld specific (e.g., weld bead residue at the club head 42) may be performed before proceeding to the next step. In a next step, the sealing assembly 60 is slidably mounted around the piston rod 30. Subsequently, after installation of the seal assembly 60, the piston 50 is friction welded to the proximal rod end 31 of the piston rod 30. The step of friction welding is performed by advantageously using a particular configuration of the proximal rod end 31 and the piston 50 to prevent contamination or damage to the seal assembly 60 that has been installed around the piston rod 30.

An embodiment of this particular configuration is shown in fig. 3A-3C.

Fig. 3A and 3B illustrate the proximal rod end 31 of the piston rod 30 in cross-section, which shows successive steps of friction welding the piston 50 to the rod end 31 of the piston rod 30.

Fig. 3A shows the piston rod 30 and the piston 50 as separate components prior to friction welding.

The plunger rod 30 has a narrowed portion 39 at the proximal end 31. The piston rod 30 has a main rod diameter 38 along its length. Preferably, the piston rod 30 has a constant rod diameter along its length. Preferably, the piston rod 30 has a rod diameter 38 of at most 20 millimeters at the proximal end 31. The narrow portion 39 has a reduced diameter relative to the rod diameter 38. And an annular surface 380 between the narrow portion 39 and the remainder of the piston rod 30 defines the narrow portion 39.

The narrow portion 39 is referred to as a flare portion. The flash portion 39 is used to perform a friction welding operation. The flash portion 39 has an end face serving as a flash surface 390. The flash surface is the contact surface during a friction welding operation. Flash surface 390 is an end surface of piston rod 30. Here, the piston rod 30 is solid and the flash surface 390 is circular. Alternatively, the flash portion 39 may be recessed or hollow, and the flash surface 390 may be annular. Flash portion 39 has a flash portion length "fpl" and a flash diameter "fd".

Fig. 3A further illustrates the piston 50. The piston 50 has a piston end face 51. The piston end face 51 has a recess in a central position. The recess forms a flash chamber 52 for receiving the flash portion. The flash chamber 52 has a chamber bottom 520 and chamber walls 521. The flash chamber 52 has a chamber diameter "cd" and a chamber depth "chd".

Fig. 3B shows the piston rod 30 and the piston 50 in contact after or during the friction welding operation. A gap may remain between the piston end face 51 and the annular surface 380 after the friction welding operation. A weld bead, also referred to as a flash bead 90, is formed around the junction area between the rod body 30 and the piston 50. The flash bead 90 is surrounded by the flash chamber 52. A flash bead 90 remains within the flash chamber 52. Advantageously, the flash bead 90 is surrounded by the flash chamber 52, helping to prevent contamination of the surrounding environment.

The flare diameter "fd" and the chamber diameter "cd" are adapted to each other such that the flare portion 39 of the piston rod 30 can be inserted into the flare chamber 52. In particular, the flare diameter "fd" is at least 1 millimeter smaller than the chamber diameter "cd". Insertion of flash portion 39 into flash chamber 52 results in a flash gap "fc" of at least 1 mm between flash portion 39 and chamber wall 521. The flash gap "fc" is configured to receive the flash bead 90.

The flash portion has a flash portion length "fpl" and the flash chambers have flash chamber depths "chd" that are adapted to each other. The flash portion length "fpl" is greater than the flash chamber depth "chd". In particular, the flash portion length "fpl" is at least 1 millimeter greater than the flash chamber depth "chd" such that during friction welding, at least 1 millimeter of material is displaced from the flash surface 390 and/or the chamber bottom before the piston end face 51 contacts the annular surface 380 of the piston rod 30. Thus, the desired strong joint area can be obtained by welding. A volume of material will be produced to obtain the friction weld bead 90. The friction weld bead 90 is surrounded by the flash chamber 52. When the piston 50 is in close proximity to or even in contact with the annular surface 380, the flash chamber 52 may be substantially or even completely closed, which helps to substantially reduce released weld residue.

Figure 3C shows another embodiment of the piston and piston rod assembly 20 in cross-section. The piston rod 30 is provided with a centering portion 37. The centering portion 37 is positioned beside the flash portion 39, in particular adjacent to the flash portion 39. The centering portion 37 is adapted to center the piston 50 relative to the piston rod 30. During the friction welding step, the piston rod 30 is axially moved toward the piston 50. The flash portion 39 of the piston rod 30 is received in the flash chamber 52 of the piston 50. During friction welding, the centering portion 37 is also received in the flash chamber 52. The outer diameter of the centering portion 37 corresponds to the inner diameter of the flash chamber 52, such that the piston 50 is centered with respect to the piston rod 30 when the centering portion 37 enters the flash chamber 52. In addition to centering the piston, another advantage of the centering portion is that the flash chamber can be kept completely closed during the friction welding process. This may eliminate any release of welding residues and may prevent any contamination of the environment.

In particular, the invention relates to the field of automotive technology. The linear actuator 10 according to the invention provides a beneficial contribution in a heavy load environment. The linear actuator 10 is preferably embodied as a hydraulic cylinder provided with a welding head 40.

Fig. 4 shows a vehicle 1 comprising a tiltable cab, a so-called tilting cab 2, arranged on a chassis 3. The vehicle is provided with a tilting system 4 for tilting the tilting cab 2 from a lowered position to a raised position relative to the chassis 3. The tilting system 4 comprises a pivot and a tilting cylinder 5. According to the invention, the tilting cylinder 5 is configured as shown in fig. 1-3. The tilting cylinder 5 is a double acting hydraulic cylinder. The tilt cylinder 5 comprises a cylinder housing 11, wherein a cylinder base 111 is pivotally connected to the chassis 3, and wherein the rod head 40 is connected to the cab 2.

Fig. 5 schematically shows the tilting system 4 in more detail. The tilting system 4 comprises a double acting cylinder 5. The double acting cylinder 5 comprises a cylinder block 110, wherein a pulling chamber 12 and a pushing chamber 13 are defined by a movable piston 50. The piston 50 is secured to the piston rod 30 by friction welding, which together form the piston and piston rod assembly 20. The pull chamber 12 and the push chamber 13 are fluidly connected to the control valve 15, the pump 16, and the reservoir 17 by hydraulic lines 120, 130, respectively, to extend or retract the piston and piston rod assembly 20. Here, the control valve 15 is an on-off valve that switches between the pressurizing and releasing operation steps.

Accordingly, the present invention provides a piston and piston rod assembly for a linear actuator manufactured by a friction welding method. The piston rod includes a flash portion formed by a narrow portion having a flash surface formed by an end face. The piston includes a flash chamber formed by a centrally located recess. In the friction welding method, a flash portion is inserted into a flash chamber, and relative rotation and axial pressure are applied between a piston rod and a piston so that a flash surface is bonded to the bottom of the chamber. Advantageously, a clean welding step is provided, which allows for the pre-placement of the sealing assembly around the piston rod. A seal assembly including a wiper, a seal ring, and a seal gland may be placed around the piston rod before the clean welding step is performed.

List of reference numerals:

1 vehicle 112 eye connector

2 inclined cab 12 pull cab

3 chassis 120 hydraulic line

4 tilting system 13 push chamber

5 tilting cylinder 130 hydraulic line

15 control valve

10 linear actuator 16 pump

11 cylinder housing 17 reservoir

110 cylinder

111 cylinder base 20 piston and piston rod assembly

30 piston rod

31 proximal rod end

32 distal rod end

37 centering portion

38 rod diameter

380 annular surface

39 flash portion

390 sparkling surface

fpl flash part length

fd flash diameter

40 head

41 pole end face

44-hole connecting piece

50 piston

51 piston end face

52 a piston recess; flash chamber

520 chamber bottom

521 chamber wall

cd chamber diameter

chd Chamber depth

60 seal assembly

61 sealing gland

62 sealing ring

63 wiper

90 flash bead

fc flash gap