PISTON UNIT OF A WORKING CYLINDER

Abstract

A piston unit of a working cylinder includes a piston rod that has an outer thread on a piston-side coupling portion. A piston has an axial bore which has an inner thread and in which the piston rod is received. The outer thread and the inner thread define a common thread portion. The outer thread and the inner thread have a complementary conicity and a complementary thread geometry. The conicity has a conicity angle alpha of 0.3 to 5 degrees. The outer thread and the inner thread abut one another in a coupling end position in the thread portion in a gap and define a sealing plane. The outer thread and the inner thread have, in the thread portion in the coupling end position, an elastic deformation within the elastic limit of the piston rod and the piston. The elastic deformation is brought about by a surface pressure via a tightening torque. The piston rod and the piston are radially and axially fixed to one another without play in the coupling end position by the elastic deformation, and the elastic deformation is within the elastic limit both with and without an application of pressure by a pressure medium in the working cylinder.

Claims

1.-4. (canceled)

5. A piston unit of a working cylinder, comprising: a piston rod and a piston, said piston rod having an outer thread at a coupling section on a piston side thereof, said piston having an axial bore having an inner thread, said axial bore receiving said piston rod therein, said outer thread and the inner thread defining a common thread section; said outer thread and said inner thread each having a respective taper, said taper of said outer thread and said taper of said inner thread matching with one another, said tapers having a taper angle of 0.3 to 5 degrees relative to a main longitudinal axis of said piston rod, said outer thread and said inner thread having a matching thread geometry; said outer thread and said inner thread being constructed for abutting against each other in a clearance-free manner in said common thread section when in a coupling end position and defining a sealing plane by the clearance-free manner; said outer thread and said inner thread having an elastic deformation within the elastic limits of said piston rod and said piston with said common thread section in the coupling end position, the elastic deformation occurring by a surface pressure through a tightening torque, and in the coupling end position, said piston rod and said piston being fixed to one another radially and axially without clearance by the elastic deformation and the elastic deformation being within the elastic limits with and without pressurization by a pressure medium in the working cylinder.

6. The piston unit of the working cylinder according to claim 5, wherein said taper has a taper angle of 0.5 to 1.5 degrees.

7. The piston unit of the working cylinder according to claim 5, wherein said thread flanks have an inclination angle of 55 to 100 degrees.

8. The piston unit of the working cylinder according to claim 5, comprising a sealing body with a radial inner ring surface, said sealing body arranged in the thread section in the inner thread of the piston, and a radial inner ring surface of the sealing body having a sealing body thread section defining an axial subsection of said common thread section.

Description

[0036] The invention is described as an exemplary embodiment in more detail by the following figures:

[0037] FIG. 1 Sectional view of the working cylinder with piston unit

[0038] FIG. 2 Detailed sectional view of the thread section

[0039] FIG. 3 Detailed sectional view of the thread section with sealing body

[0040] Hereinafter, the use of the reference numerals in the figures and in the associated description sections is consistent in the following, even if not all figures are provided with all reference numerals.

[0041] FIG. 1 shows a sectional view of the working cylinder 1. In this example, it is a double-acting hydraulic cylinder designed as a differential working cylinder.

[0042] It has, in particular, a piston unit 2. The piston unit 2 is composed of the piston rod 3 and the piston 4. A conical outer thread 5 is provided at the piston rod 3 at one end on the piston side. The piston 4 is screwed onto this conical outer thread 5 by means of the inner thread 6. The inner thread also has a taper. The taper angle of both the outer thread 5 and the inner thread 6 is 1 degree. The outer thread 5 and the inner thread 6 engage into each other in a common thread section 7.

[0043] FIG. 2 shows the detailed view of a part of the common thread section 7. The thread shape of the outer thread 5 of the piston rod 3 is the same as the thread shape of the inner thread 6, so that they abut against each other without any clearance. The inclination angle is 90 degrees and the taper angle is 0.75 degrees.

[0044] The basic shape of both threads 5, 6 formed by the average thread diameter is conical along the axial thread length. The conical shape of both threads 5, 6 allows the piston 4 to be screwed onto the piston rod 3 up to a certain position. After that, the thread flanks form a positive locking connection which also has a fluid-sealing effect. In addition, the screw-in path is continued by applying a tightening torque until a radial concentric elastic deformation of the piston rod 3 and a radial eccentric elastic deformation of the piston 4 are produced. At the same time, an axial elastic deformation of the piston rod 3 is effectuated as an elongation and an axial elastic deformation of the piston 4 is effectuated as a compression. The axial elastic deformations are indicated by the vertical arrows. The diagonal arrows pointing to each other indicate the additional surface pressure on the thread flanks and thus the elastic axial tension between the piston rod 3 and the piston 4.

[0045] FIG. 3 shows the detailed view of a part of the common thread section 7 in an exemplary embodiment provided with a sealing body 8. With the exception of the sealing body 8, the basic structure corresponds to FIGS. 1 and 2, so that in this respect reference is additionally made to these figures and the associated description sections.

[0046] Furthermore, FIG. 3 shows an exemplary embodiment in a further variant of the geometry of the outer thread 5 and the inner thread 6. The thread tips and thread sinks are flattened here and form a trapezoidal thread. A positive locking and clearance-free thread engagement is also achieved here.

[0047] In addition, a sealing body 8 is inserted into a recess in the inner lateral surface of the axial bore in the piston 4. This body is made of an elastomeric material. The outer thread of the piston rod 3 abuts in a corresponding manner against that of the sealing body 8 in a press fit. This design produces a sealing and positive locking connection.

LIST OF REFERENCE NUMERALS

[0048] 1 working cylinder [0049] 2 piston unit [0050] 3 piston rod [0051] 4 piston [0052] 5 outer thread [0053] 6 inner thread [0054] 7 common thread section [0055] 8 sealing body [0056] 9 sealing body thread section [0057] taper angle alpha [0058] thread flank inclination angle beta