SPRING SLEEVE, CYLINDER, PISTON CYLINDER UNIT AND METHOD OF MANUFACTURING A PISTON CYLINDER UNIT

Abstract

Provided is a spring sleeve for a piston cylinder unit, wherein the spring sleeve is adapted to receive a spring, at least partially, and to guide it, wherein the spring sleeve has a cylindrical sleeve inner surface. The embodiment further relates to a cylinder for a piston cylinder unit, wherein the cylinder) is adapted to be arranged inside a spring of a piston cylinder unit. The embodiment also relates to a piston cylinder unit, including a cylinder, a spring arranged concentrically around the cylinder, and an inner spring sleeve and outer spring sleeve each arranged concentrically around the spring, wherein the cylinder and the spring are arranged inside the inner spring sleeve and the outer spring sleeve. Finally, the embodiment relates to a method of manufacturing such a piston cylinder unit.

Claims

1. A spring sleeve for a piston cylinder unit, wherein the spring sleeve is adapted to receive a spring, at least partially, and to guide it along a spring path of the piston cylinder unit, wherein the spring sleeve comprises a cylindrical sleeve inner surface, wherein a. the spring sleeve comprises a number of grooves on its sleeve inner surface, and b. a longitudinal axis of the grooves is oriented in an axial direction parallel to the stroke path of the piston cylinder unit, wherein c. the depth of the grooves varies along the axial direction.

2. The spring sleeve according to claim 1, wherein the spring sleeve having a synthetic blend comprising a plastic of polyamide, and additions of polytetrafluoroethylene, wherein the proportion of polytetrafluoroethylene lies in a range of 10% to 30%, or of polyamide fiber-reinforced with carbon fibers, glass fibers and/or plastic fibers.

3. The spring sleeve according to claim 1, wherein the spring sleeve comprises a cylindrical sleeve base layer and a sleeve surface layer, wherein the grooves are arranged in the sleeve surface layer, and wherein the sleeve base layer and the sleeve surface layer consist of different materials.

4. A cylinder for a piston cylinder unit, wherein the cylinder is adapted to be arranged inside a spring of a piston cylinder unit, wherein a. the cylinder has a number of grooves on its cylinder outer surface, and b. a longitudinal axis of the grooves is oriented in an axial direction parallel to a stroke path of the piston cylinder unit, wherein c. the depth of the grooves varies along the axial direction.

5. The cylinder according to claim 4, wherein the cylinder comprises a cylindrical cylinder base layer and a cylinder surface layer, wherein the grooves are arranged in the cylinder surface layer, and wherein the cylinder base layer and the cylinder surface layer includes different materials.

6. A piston cylinder unit, comprising: a cylinder, a spring arranged concentrically around the cylinder, an inner spring sleeve and an outer spring sleeve each arranged concentrically around the spring, wherein the cylinder and the spring are arranged inside the inner spring sleeve and the outer spring sleeve, and the inner spring sleeve and/or the outer spring sleeve and/or the cylinder has a number of grooves on the surface facing the spring, wherein a longitudinal axis of the grooves is oriented in an axial direction parallel to a stroke path of the piston cylinder unit, wherein the depth of the grooves varies along the axial direction.

7. The piston cylinder unit according to claim 6, wherein at least one surface of the inner spring sleeve and/or the outer spring sleeve and/or the cylinder is friction-optimized with respect to the material of the spring by the material choice of a cylinder surface layer of the cylinder and/or of a sleeve surface layer of the inner spring sleeve and/or of a sleeve surface layer of the outer spring sleeve.

8. A method of manufacturing a piston cylinder unit, comprising: a cylinder, a spring arranged concentrically around the cylinder, an inner spring sleeve and an outer spring sleeve each arranged concentrically around the spring, comprising by the following steps: introduction of a number of grooves into: the inner spring sleeve and/or the outer spring sleeve and/or the cylinder on a surface facing the spring, by injection molding, an additive method or a subtractive method, wherein the grooves are introduced with a longitudinal axis oriented in an axial direction parallel to a stroke path of the piston cylinder unit, wherein the grooves are introduced with a depth varying along the axial direction.

9. The method according to claim 8, having the following step: production of the inner spring sleeve and/or the outer spring sleeve by coating a cylindrical sleeve base layer with a sleeve surface layer, wherein the grooves are introduced into the sleeve surface layer.

10. The method according to claim 8, having the following step: production of the cylinder by coating a cylindrical cylinder base layer with a cylinder surface layer, wherein the grooves are introduced into the cylinder surface layer.

Description

BRIEF DESCRIPTION

[0068] Some of the embodiments will be described in detail, with reference to the following figures, wherein like designations denote like members, wherein:

[0069] FIG. 1 a schematic sectional view of a piston cylinder unit as well as a spring sleeve and a cylinder;

[0070] FIG. 2 a sectional view along the plane A-A of FIG. 1 of a piston cylinder unit;

[0071] FIG. 3 a schematic sectional view of the section B1, B2 or B3 from FIG. 1 in a first embodiment;

[0072] FIG. 4 a schematic sectional view of the section B1, B2 or B3 from FIG. 1 in a second embodiment;

[0073] FIG. 5 a schematic sectional view of the section B1, B2 or B3 from FIG. 1 in a third embodiment; and

[0074] FIG. 6 a schematic sectional view of the section B1, B2 or B3 from FIG. 1 in a fourth embodiment.

DETAILED DESCRIPTION

[0075] FIG. 1 shows a schematic sectional view of a piston cylinder unit 1 according to embodiments of the invention, comprising a cylinder 2, a spring 3, an outer spring sleeve 4 and an inner spring sleeve 5. The two spring sleeves 4, 5 are arranged concentrically around the centrally arranged cylinder 2. The spring 3 is supported and guided between the two spring sleeves 4, 5 partially engaging in one another and the cylinder 2. The outer spring sleeve 4 has a larger inner diameter than the outer diameter of the inner spring sleeve 5, due to which the inner spring sleeve 5 can penetrate further into the outer spring sleeve 4 in the event of loading of the piston cylinder unit 1.

[0076] In the inside of the cylinder 2, there can be arranged, for example, a gas pressure spring, or the cylinder 2 can be part of a gas pressure spring. The cylinder 2 can also consist of several cylinder segments, which can partially penetrate into one another, in order to shorten or lengthen the cylinder 2. The cylinder 2 is therefore depicted here in one piece purely for the sake of simplicity.

[0077] FIG. 2 shows a sectional view along the section plane A-A in FIG. 1. Here only one embodiment of the invention is shown as an example, which only has axial grooves 6 in the inner spring sleeve 5.

[0078] The axial grooves in the sleeve inner surface reduce the overall area of the spring sleeve that is provided as friction partner with the spring 3 to be guided. The spring 3 is represented here by a circular ring with a hatched section, in order to clarify the reduction in the friction area with the inner spring sleeve 5. The dotted lines represent the contour of an alternative inner spring sleeve 5 without axial grooves 6.

[0079] The axial grooves 6 also serve as a reservoir for a lubricant used in the piston cylinder unit 1. By means of surface tension effects of the lubricant, the grooves 6 hold a portion of the lubricant, even if the remainder of the lubricant collects at the lower end of the piston cylinder unit 1 due to gravity. This effect can be optimized by coordination of the geometrical dimensions of the grooves to the lubricant.

[0080] FIGS. 3-6 show simplified schematic sectional views of the plane regions B1, B2 and B3 of FIG. 1. The structures depicted can thus correspond to the contact region between the spring 3 and the inner spring sleeve 5 (B1) or the spring 3 and the outer spring sleeve 4 (B2) or the spring 3 and the cylinder 2 (B3).

[0081] FIG. 3 shows a schematic sectional view of a contact region between the spring 3 and the surface of one of the spring sleeves 4, 5 or of the cylinder 2 in the area of an axial groove 6. As is recognizable, the spring 3 is in contact with the friction partner outside the groove area, while in the area shown it is not in direct contact. The overall surface of the spring sleeve 4, 5 or of the cylinder 2 that is available as friction partner with the spring 3 is thus reduced. A lubricant can be introduced, furthermore, into the axial grooves 6. The grooves then act as a reservoir for the lubricant and prevent the lubricant from collecting completely at one end of the piston cylinder unit 1 when the piston cylinder unit is inactive for a long time. The axial groove 6 in this embodiment has a constant depth H1 along the axial direction (in a horizontal direction in each case in FIGS. 3-6).

[0082] FIG. 4 shows another schematic sectional view of a contact region between the spring 3 and the surface of one of the spring sleeves 4, 5 or of the cylinder 2 in the area of an axial groove 6. In contrast to the previous embodiment, the axial groove 6 has a varying depth in an axial direction here. The depth of the groove 6 varies between a smallest depth H2 at a groove maximum 7 and a greatest depth H3 at a groove minimum 8. The axial groove 6 in this embodiment has a periodically varying depth, for example with a sinusoidal profile.

[0083] FIG. 5 shows yet another schematic sectional view of a contact region between the spring 3 and the surface of one of the spring sleeves 4, 5 or of the cylinder 2 in the area of an axial groove 6. As in FIG. 3, the axial groove 6 in this embodiment has a constant depth H1.

[0084] The spring sleeve(s) 4, 5 and/or the cylinder 2 have at least two layers in this embodiment, however.

[0085] The outer spring sleeve 4 and/or the inner spring sleeve 5 has a sleeve base layer 9 and a sleeve surface layer 10 and/or the cylinder has a cylinder base layer 11 and a cylinder surface layer 12.

[0086] The axial groove 6 is arranged completely in the sleeve surface layer 10 or the cylinder surface layer 12. The axial groove 6 can be introduced, for example, when applying the sleeve surface layer 10 or the cylinder surface layer 12 to the respective base layer 9, 11.

[0087] The respective base layer 9, 11 can consist of a mechanically particularly durable and stable material, for example of glass-fiber-reinforced polyamide. The respective surface layer 10, 12 can consist of a material with reduced friction relative to the material of the spring 3 (for example, spring steel), for example of a synthetic blend comprising polyamide and additions of polytetrafluoroethylene.

[0088] FIG. 6 shows yet another schematic sectional view of a contact region between the spring 3 and the surface of one of the spring sleeves 4, 5 or of the cylinder 2 in the area of an axial groove 6. Like in the embodiment in FIG. 4, the axial groove 6 has a varying depth in an axial direction here. The depth of the groove 6 varies between a smallest depth H2 at a groove maximum 7 and a greatest depth H3 at a groove minimum 8.

[0089] The spring sleeve(s) 4, 5 and/or the cylinder 2 in this embodiment have at least two layers, as was the case in the embodiment in FIG. 5.

[0090] The outer spring sleeve 4 or the inner spring sleeve 5 have a sleeve base layer 9 and a sleeve surface layer 10, or the cylinder has a cylinder base layer 11 and a cylinder surface layer 12. The corresponding also applies here as for FIG. 5 with regard to the choice of material.

[0091] The axial groove 6 in this embodiment has a periodically varying depth, for example with a sinusoidal profile.

[0092] Although the present invention has been disclosed in the form of preferred embodiments and variations thereon, it will be understood that numerous additional modifications and variations could be made thereto without departing from the scope of the invention.

[0093] For the sake of clarity, it is to be understood that the use of a or an throughout this application does not exclude a plurality, and comprising does not exclude other steps or elements. The mention of a unit or a module does not preclude the use of more than one unit or module.

REFERENCE SIGN LIST

[0094] 1 Piston cylinder unit

2 Cylinder

3 Spring

[0095] 4 Outer spring sleeve
5 Inner spring sleeve

6 Groove

[0096] 7 Groove maximum
8 Groove minimum
9 Sleeve base layer
10 Sleeve surface layer
11 Cylinder base layer
12 Cylinder surface layer