Drive unit of a fluid-actuated linear drive and method for its manufacture

1. A drive unit of a fluid-actuated linear drive, comprising a piston rod, an annular drive piston seated coaxially on the piston rod and a buffer sleeve which is likewise seated coaxially on the piston rod while axially adjoining the drive piston and which is used for end-of-stroke cushioning purposes, wherein the drive piston, the buffer sleeve and the piston rod are secured to one another by one and the same common welded joint, the common welded joint being formed in a contact region between the buffer sleeve and the drive piston, the contact region having an annular shape concentric with the piston rod, and wherein the common welded joint extends radially inward through the contact region between the drive piston and the buffer sleeve and into the material of the piston rod.

2. A drive unit according to claim 1 , wherein two buffer sleeves flanking the drive piston on axially opposite sides are seated on the piston rod, each buffer sleeve being permanently joined to the drive piston and the piston rod by means of its own common welded joint.

3. A drive unit according to claim 1 , wherein the common welded joint comprises a fluid-tight weld seam which is concentric with the piston rod and by means of which both the drive piston is welded to the buffer sleeve and both these components are simultaneously welded to the piston rod.

4. A drive unit according to claim 1 , wherein the common welded joint is a laser beam weld or an electron beam weld.

5. A drive unit according to claim 1 , wherein the common welded joint is formed directly between the welded components without the use of any added material.

6. A drive unit according to claim 1 , wherein the components secured to one another by the common welded joint are made of metal at least in the regions participating in the welded joint.

7. A drive unit according to claim 1 , wherein at least the piston rod and/or each buffer sleeve is/are made of metal.

8. A drive unit according to claim 1 , wherein the drive piston has a single-part or multi-part piston body which is made of metal, which participates in the common welded joint and which supports at least one sealing element.

9. A drive unit according to claim 1 , wherein the piston rod is designed to be tubular.

10. A drive unit of a fluid-actuated linear drive, comprising a piston rod, an annular drive piston seated coaxially on the piston rod and a buffer sleeve which is likewise seated coaxially on the piston rod while axially adjoining the drive piston and which is used for end-of-stroke cushioning purposes, wherein the drive piston, the buffer sleeve and the piston rod are secured to one another by one and the same common welded joint, and

wherein the drive piston has, on the end face facing the buffer sleeve, an axial mounting projection which is concentric with the piston rod and against which the adjacent buffer sleeve bears axially, the common welded joint being formed in the transition region between the mounting projection and the buffer sleeve and extending between the axial mounting projection and the buffer sleeve into the piston rod, the outer diameter of the mounting projection corresponding to the outer diameter of the facing axial end section of the buffer sleeve.

11. A fluid-actuated linear drive, comprising a drive housing and a drive unit which is axially movable relative to the drive housing, the drive unit comprising:

a piston rod;

an annular drive piston seated coaxially on the piston rod, the annular drive piston being capable of linear displacement in the drive housing; and

a buffer sleeve which is likewise seated coaxially on the piston rod while axially adjoining the drive piston and which is used for end-of-stroke cushioning purposes,

wherein the drive piston, the buffer sleeve and the piston rod are secured to one another by one and the same common welded joint, and

wherein the drive piston has, on the end face facing the buffer sleeve, an axial mounting projection which is concentric with the piston rod and against which the adjacent buffer sleeve bears axially, the common welded joint being formed in the transition region between the mounting projection and the buffer sleeve and extending between these two components into the piston rod, the outer diameter of the mounting projection corresponding to the outer diameter of the facing axial end section of the buffer sleeve.

12. A method for the manufacture of a drive unit of a fluid-actuated linear drive which comprises a piston rod, an annular drive piston seated coaxially on the piston rod and a buffer sleeve which is likewise seated coaxially on the piston rod while axially adjoining the drive piston and which is used for end-of-stroke cushioning purposes, the method comprising:

pushing the drive piston and the buffer sleeve onto the piston rod which has been provided previously, the drive piston having an end face facing the buffer sleeve and an axial mounting projection concentric with the piston rod on the end face, the buffer sleeve axially bearing against the axial mounting projection of the drive piston; and

simultaneously welding the drive piston, the buffer sleeve and the piston rod to form a common welded joint, the common welded joint being formed in a transition region between the axial mounting projection and the buffer sleeve and extending between the axial mounting projection and the buffer sleeve into the piston rod, the outer diameter of the axial mounting projection corresponding to the outer diameter of the facing axial end section of the buffer sleeve.

13. A method according to claim 12 , wherein two buffer sleeves are pushed onto the piston rod in such a way that they flank the drive piston on axially opposite sides, each buffer sleeve being welded to the drive piston and the piston rod while forming an own common welded joint.

14. A method according to claim 12 , wherein the common welded joint is produced by means of a fluid-tight weld seam which is concentric with the piston rod and by means of which both the drive piston is welded to the buffer sleeve and both these components are simultaneously welded to the piston rod.

15. A method according to claim 12 , wherein the common welded joint is produced as a laser beam weld or an electron beam weld.