Piston unit of a working cylinder

Abstract

A piston unit of a working cylinder includes a piston and a piston rod. The piston has an axial bore hole formed therein. The piston rod is received in the axial bore hole. The piston rod and the piston are connected by a material-bond by a circumferential laser ring weld seam. The laser ring weld seam defines a pressure medium-tight sealing plane.

Claims

1. A piston unit of a working cylinder, comprising: a piston and a piston rod, said piston having an axial bore hole formed therein, said piston rod having a chromium-plated outer lateral surface, said piston rod being received in said axial bore hole, said piston rod and said piston being connected with a material-bond by a circumferential laser ring weld seam, said laser ring weld seam defining a pressure medium-tight sealing plane; and said outer lateral surface having a non-chromium-plated cross-sectionally reduced annular section, an annular compensation layer arranged between said piston and said cross-sectionally reduced annular section, said laser weld ring seam including a radial inner laser ring weld seam connecting said piston rod to said annular compensation layer and a radial outer laser ring weld seam connecting said annular compensation layer to said piston.

Description

BRIEF DESCRIPTION OF THE FIGURES

(1) FIG. 1 Piston unit of a working cylinder (welded on the bottom side)

(2) FIG. 2 Piston unit of a working cylinder (welded on the piston rod side)

(3) FIG. 3 Piston unit of a working cylinder (closed piston)

(4) FIG. 4 Piston unit of a working cylinder (welded on both sides)

(5) FIG. 5 Piston unit of a synchronized cylinder (welded on both sides)

(6) FIG. 6 Piston unit of a working cylinder (with annular compensation layer)

(7) FIG. 7 Piston unit with hardened piston surface (exploded view)

(8) FIG. 8 Piston unit with hardened piston surface (welded).

DETAILED DESCRIPTION OF THE INVENTION

(9) FIG. 1 shows a first embodiment of a piston unit of a working cylinder in a schematic sectional view. The piston unit comprises a piston 1 and a piston rod 2. The piston 1 has an axial bore hole 3 in which the piston rod 2 is received. It has a bottom side 5 and a piston rod side 8.

(10) The piston unit has a laser ring weld seam 4 which connects the piston 1 and the piston rod 2 in a material-bonding manner. The laser weld seam 4 is arranged on the bottom side 5.

(11) The laser ring weld seam 4 has a weld seam center axis 6 which runs centrally through the cross-section of the laser ring weld seam 4.

(12) This weld seam center axis 6 runs parallel to the main center axis 7 of the piston rod 2 and along the corresponding contact surfaces of the piston 1 and piston rod 2.

(13) In this embodiment, welding is performed from the bottom side 5 by means of a laser welding process. Laser welding processes, in which the weld seam center axis 6 runs parallel to the main longitudinal axis 7, are possible on the bottom side due to the required freedom of movement of the laser emitter.

(14) FIG. 2 shows another embodiment of a piston unit which is welded on the piston rod side. Here, the laser ring weld seam 4 is inclined at an inclination angle of 5 degrees. In all other respects, the piston unit illustrated in FIG. 2 is identical in construction to the piston unit shown in FIG. 1.

(15) Due to the piston rod 2, the laser is inclined at the inclination angle relative to the main longitudinal axis 7 of the piston rod 2. Thus, the weld seam center axis 6, which corresponds to the course of the laser beam, is not parallel to the main center axis 7 as in FIG. 1 and includes the inclination angle with it.

(16) In this embodiment, the edge area of the laser ring weld seam 4 overlaps with the contact surfaces between the piston 1 and piston rod 2, thus producing the joint between them.

(17) FIG. 3 shows a piston unit with a closed piston 1. In contrast to the previous piston units, the axial bore hole 3 does not penetrate the piston 1 but is designed as a blind bore hole. Here, the piston rod 2 is not completely guided through the piston 1.

(18) The laser ring weld seam 4 is arranged analogously to the one in FIG. 2 on the piston rod side and with a bevelled weld seam center axis 6, which includes the inclination angle with the main center axis 7. The inclination angle is also 5 degrees here.

(19) The piston unit shown in FIG. 4 substantially corresponds to the piston units in FIG. 1 and FIG. 2.

(20) In this embodiment, the connection of the piston 1 to the piston rod 2 is established by a first laser ring weld seam 4.1 and a second laser ring weld seam 4.2.

(21) The first laser ring weld seam 4.1 corresponds to the laser ring weld seam 4 of FIG. 1, in which the weld seam center axis 6 runs parallel to the main longitudinal axis 7, and welding is performed from the bottom side 5.

(22) The second laser ring weld seam 4.2 corresponds to the laser ring weld seam 4 of FIGS. 2 and 3, in which the weld seam center axis 6 and the main longitudinal axis 7 include the inclination angle . Here, the inclination angle is also 5 degrees. Here, welding is done from the piston rod side 8

(23) In this embodiment, the first laser ring weld seam 4.1 and the second laser ring weld seam 4.2 contact or overlap each other, resulting in a joint over the entire cylindrical contact surface of the piston 1 and piston rod 2. Thus, a maximum load capacity of the connection is obtained.

(24) FIG. 5 shows a piston unit of a synchronized cylinder. The special feature of the synchronized cylinder is that it does not have a bottom side 5 due to the passing piston rod 2. For this reason, the two sides are defined as a first piston rod side 8.1 and a second piston rod side 8.2. In this embodiment, both piston rod sides 8.1, 8.2 are of the same design.

(25) In contrast to the other embodiments of the piston units, both the first laser ring weld seam 4.1 and the second laser ring weld seam 4.2 are bevelled by the inclination angle relative to the main longitudinal axis. Here, the inclination angle is also 5 degrees.

(26) In this design, the first laser ring weld seam 4.1 is laser-welded from the first piston rod side 8.1 and the second laser ring weld seam 4.2 is laser-welded from the second piston rod side 8.2.

(27) FIG. 6 shows a piston unit with an annular compensation layer 10. In this embodiment, the surface of the piston rod 2 is chromium-plated.

(28) The surface in an annular section 9 is removed by turning to such an extent that a section with a reduced cross-section is formed. For reasons of clarity, the degree of cross-section reduction is shown in an exaggerated view in FIG. 6. The annular compensation layer 10, which is designed as a segmented steel sleeve in this embodiment, is inserted into this cross-sectionally reduced annular section 9. The piston 1 is pushed over the annular compensation layer 10.

(29) The piston rod 2 is welded to the annular compensation layer 10 by means of the radial inner laser weld seam 11. The annular compensation layer 10 is materially homogeneous to the piston rod 2 under the chromium layer and to the piston 1. Here, the weld seam center axis 6 is inclined at the inclination angle . The inclination angle is 5 degrees.

(30) The piston 1 is welded to the annular compensation layer 10 by means of the radial outer laser weld seam 12. The weld seam center axes 6 of the radial outer laser weld seam and the radial inner laser weld seam 11 run parallel.

(31) FIG. 7 shows a piston unit with a piston 1 which has a hardened surface 16.

(32) Furthermore, the piston 1 has a flat cylindrical machine-molded section 14, which projects slightly over the rest of the contour of the piston 1 on the piston rod side 8.

(33) The hardened surface is removed from the axial mating contact surface 15 in the area of the flat cylindrical machine-molded section 14 by surface grinding. In the center of the flat cylindrical machine-molded section 15 there is a centring bore hole which corresponds with a centring pin in the center of the axial contact surface 13 of the piston rod 2.

(34) In this way, the piston 1 can be placed on the piston rod 2, and thus both are fixed in their relative radial position.

(35) FIG. 8 shows the completely assembled piston unit of FIG. 7. The piston 1 has been placed axially on the piston rod 2 so that the contact surface 13 and the mating contact surface 14 are in contact. The centring pin is in engagement with the centring bore hole.

(36) The piston 1 and the piston rod 2 are connected along the corresponding contact surfaces 13, 14 by means of the laser ring weld seam 4.

(37) Compared to the previously described piston units, the weld seam center axis 6 runs perpendicular to the main longitudinal axis.

LIST OF REFERENCE NUMERALS

(38) 1 piston 2 piston rod 3 axial bore hole 4 laser ring weld seam 4.1 first laser ring weld seam 4.2 second laser ring weld seam 5 bottom side 6 weld seam center axis 7 main longitudinal axis 8 piston rode side 8.1 first piston rode side 8.2 second piston rode side 9 cross-sectionally reduced annular section 10 annular compensation layer 11 radial inner laser weld seam 12 radial outer laser weld seam 13 axial contact surface 14 flat cylindrical machine-molded section 15 axial mating contact surface 16 hardened surface inclination angle alpha