Actuating Piston and Adjustment Installation

Abstract

An actuating piston for a hydrostatic adjustment installation includes at least one sealing and guiding unit which is insertable into a circumferential recess of an actuating piston. The circumferential recess is composed of two regions, and has the effect of improving the guiding and sealing of the actuating piston. The actuating piston is arranged in an adjustment installation.

Claims

1. An actuating piston for a hydrostatic adjustment installation comprising: an external shell face defining a circumferential recess; and a sealing and guiding unit encompassing the external shell face in a region of the circumferential recess, the sealing and guiding unit configured to guide the actuating piston in an actuating cylinder of the hydrostatic adjustment installation so as to be stable in terms of tilting and displaceable in an axial manner, and to seal a gap between the external shell face of the actuating piston and an internal shell face of the actuating cylinder, wherein the circumferential recess has a first region having a guide region for the sealing and guiding unit that is configured to absorb transverse forces, and a second region having protrusions, and wherein the first region has a larger axial extent than the second region.

2. The actuating piston according to claim 1, wherein an axial extent of the guide region is larger by a multiple than an axial extent of the protrusions.

3. The actuating piston according to claim 1, wherein the sealing and guiding unit is configured so as to be integral.

4. The actuating piston according to claim 1, wherein the protrusions in the second region, when viewed in a direction of an axial force resulting from an actuating pressure, have a decreasing diameter.

5. The actuating piston according to claim 1, wherein the protrusions push at least partially into a circumference of the sealing and guiding unit so as to engage behind the sealing and guiding unit, and/or the protrusions plunge into recesses of the sealing and guiding unit.

6. The actuating piston according to claim 1, wherein the protrusions have end face portions that absorb axial forces acting on the sealing and guiding unit, the protrusions configured to seal a gap between the external shell face of the actuating piston and the internal shell face of the actuating cylinder.

7. The actuating piston according to claim 5, wherein the protrusions push into the sealing and guiding unit during the deformation under a transverse force and/or according to wear takes place by at least 40% of an initial thickness of the sealing and guiding unit in a region of a largest protrusion of the protrusions.

8. The actuating piston according to claim 1, wherein the sealing and guiding unit, upon being applied to the actuating piston, has a sealing diameter which is at most 0.5% larger than an internal diameter of the actuating cylinder.

9. The actuating piston according to claim 1, wherein a diameter in end portions of the circumferential recess is smaller than a diameter of a contact area of the guide region.

10. The actuating piston according to claim 9, wherein the sealing and guiding unit, by way of the end portions of the circumferential recess produces a gap, which is reduced because of internal stresses of the sealing and guiding unit, the sealing and guiding unit plunging at least partially into the gap such that a chamfer is provided on the sealing and guiding unit.

11. An adjustment installation comprising: an actuating cylinder; and an actuating piston comprising: an external shell face defining a circumferential recess; and a sealing and guiding unit encompassing the external shell face in a region of the circumferential recess, the sealing and guiding unit configured to guide the actuating piston in the actuating cylinder so as to be stable in terms of tilting and displaceable in an axial manner, and to seal a gap between the external shell face of the actuating piston and an internal shell face of the actuating cylinder, wherein the circumferential recess has a first region having a guide region for the sealing and guiding unit that is configured to absorb transverse forces, and a second region having protrusions, and wherein the first region has a larger axial extent than the second region.

12. The actuating piston according to claim 1, wherein the actuating piston is configured for adjusting a displacement volume of a hydrostatic positive-displacement machine having a variable displaced volume.

13. The actuating piston according to claim 7, wherein the protrusions push into the sealing and guiding unit during the deformation under the transverse force and/or according to wear by at most 55% of the initial thickness of the sealing and guiding unit in the region of the largest protrusion.

14. The actuating piston according to claim 13, wherein the protrusions push into the sealing and guiding unit during the deformation under the transverse force and/or according to wear by at least 42% and at most 50% of the initial thickness of the sealing and guiding unit in the region of the largest protrusion.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0028] The disclosure will be explained in more detail hereunder by means of an exemplary embodiment of an adjustment installation having an actuating piston.

[0029] In the figures:

[0030] FIG. 1 shows a section through an adjustment installation;

[0031] FIG. 2 shows a detailed illustration of an adjustment installation; and

[0032] FIG. 3 shows a detailed illustration of a protrusion.

DETAILED DESCRIPTION

[0033] FIG. 1 shows an actuating cylinder 1a having an actuating piston 1 of a hydrostatic adjustment installation 2 which is illustrated in portions. The actuating piston 1 has two encircling external shell faces 4 which in a shoulder region of the actuating piston 1 have in each case one sealing and guiding unit 6 which is disposed on or in, respectively, a respective circumferential recess 8 of the actuating piston 1. The sealing and guiding unit 6 is embodied as a sealing collar and is preferably produced from an annular disk according to the method disclosed in DE 10 2017 219 361 A1 mentioned at the outset. Said annular disk is preferably formed from a fluoroplastics material, in particular from PTFE. This material has good sliding and sealing properties. In terms of further details of the production method, reference is made to the above-mentioned publication.

[0034] The actuating piston 1 is guided so as to be displaceable along a longitudinal axis 19 in a main portion 3 of an actuating cylinder 1a configured with two functions, said actuating cylinder 1a being configured so as to be integral to a housing of the positive-displacement machine to be adjusted, or configured so as to be attachable to said housing. An end-side closure of the actuating cylinder 1a is formed by a cover 10.

[0035] A spring pack 5 is disposed in a spring chamber of the actuating piston 1 on a side of the actuating piston 1 (shown on the right in FIG. 1), said spring chamber in terms of the pressurizing medium being fluidically connected to a first pressurized chamber 11 of the actuating cylinder 1a. The pressurized chamber 11 is able to be impinged with an actuating pressure in order for the pivot angle to be adjusted. A pin 7 fixed on the housing is guided along the longitudinal axis 19 through the base of the cover 10 of the actuating cylinder 1a and is fastened to said base. A bush-shaped portion of the cover 10 in the axial direction extends into the main portion 3 such that the actuating piston 1 plunges partially into the cover 10 and one of the two sealing and guiding units 6 guides the actuating piston 1 along an internal shell face of the bush-shaped portion of the cover 10.

[0036] The pressurized chamber 11 penetrated by the pin 7 is partially delimited by the cover 10 and, as mentioned above, in terms of the pressurizing medium is fluidically connected to the spring chamber of the actuating piston 1 in which the spring pack 5 is received, said pressurized chamber 11 herein being sealed in relation to a zone that is not impinged with pressure. The sealing and guiding unit 6 (on the right in FIG. 1) is disposed in the gap between the actuating piston 1 and the cover 10. As mentioned above, a sealing and guiding unit 6 which is assigned to a second pressurized chamber 21 and has the same construction as the sealing collar described above is also provided on that side of the actuating piston 1 (left in FIG. 1) that is remote from the pressurized chamber 11.

[0037] A support disk 13 and a support disk 15 are disposed so as to be displaceable on the pin 7 in the pressurized chamber 11, said support disk 13 and support disk 15 delimiting the spring pack 5. When the pressurized chamber 11 is impinged with an actuating pressure, the actuating piston 1 is moved by an axial force F.sub.A (to the left according to the illustration in FIG. 1). The support disk 13 in this movement remains locationally fixed, while the support disk 15 is entrained by the actuating piston 1 counter to a spring force of the spring pack 5.

[0038] When the second pressurized chamber 21 is impinged with an actuating pressure, the actuating piston 1 by an axial force is moved to the right, counter to the F.sub.A illustrated in FIG. 1. The support disk 13 herein is moved by the actuating piston 1 counter to the spring force of the spring pack 5, and the support disk 15 remains locationally fixed on the pin 7 which is also referred to as an actuating rod. The positive-displacement unit can thus be adjusted in equal measure in both directions.

[0039] An adjustment pin 9 of the positive-displacement machine to be adjusted, as described in the prior art according to DE 10 2017 211 750 A1 mentioned at the outset, engages with a sliding block which on one side engages in a circumferential groove of the actuating piston 1. The adjustment pin 9 is displaced by the actuating piston 1 on account of an impingement with actuating pressure, this causing an adjustment of a displacement volume of a connected hydrostatic positive-displacement machine not shown here.

[0040] The spring force of the spring pack 5 acts counter to the axial force acting during an adjustment, for example the axial force F.sub.A, and in the absence of an actuating pressure returns the actuating piston 1 to the central position thereof (illustrated in FIG. 1).

[0041] Transverse forces F.sub.Q arise on the actuating piston 1 on account of the one-sided eccentric position of the adjustment pin 9. The two sealing and guiding units 6 contribute toward the actuating piston 1 in the region of the main portion 3 and in the region of the cover 10 being guided in a stable manner in terms of tilting.

[0042] The two sealing and guiding units 6 which are in each case embodied as sealing collars have a minor wall thickness and are received in the shape of collars or sleeves in the circumferential recesses 8 of the external shell faces 4 of the actuating piston 1, said circumferential recesses 8 being adapted to said sealing and guiding units 6. A detailed description of the sealing and guiding units 6, the position, function and positioning of the latter, takes place by means of FIG. 2.

[0043] FIG. 2 shows the detail A as defined according to FIG. 1, wherein a fragment about the sealing and guiding unit 6 (on the right in FIG. 1) can be seen. The cover 10 and the main portion 3 of the actuating cylinder 1a configure an internal shell face 24 which encompasses the external shell face 4 of the actuating piston 1. A gap 12 is configured between the two shell faces 4, 24. According to FIG. 2, said gap is illustrated so as to be exaggerated for clarity. Not only the external side of the actuating piston 1 that delimits the gap 12 is referred to as the external shell face 4 at this juncture, but said external shell face 4 also comprises the circumferential recess 8 in which the sealing and guiding unit 6 is disposed.

[0044] As discussed above, the two sealing and guiding units 6 by expanding and compressing an annular disk are in each case configured in the manner of collars having a minor wall thickness, and are in each case disposed about/in the circumferential recess 8 of the actuating piston 1 (only the circumferential recess adjacent to the pressurized chamber 11 is provided with the reference sign 8 in FIG. 1). Said circumferential recess is in each case designed so as to correspond to the assigned sealing and guiding unit 6 in that said circumferential recess in the axial direction has a first region 14 and a second region 16 which are mutually spaced apart. The second region 16 has circumferential protrusions 18a, 18b, 18c which are mutually spaced apart in the axial direction and which hereunder are referred to as protrusions 18a, 18b, 18c and which, proceeding from a base 34 of the circumferential recess 8 extend in the radial direction. The number of protrusions 18a, 18b, 18c herein is not limited to the three protrusions 18a, 18b, 18c illustrated here. A smaller number as well as a larger number of protrusions is also conceivable.

[0045] The sealing and guiding unit 6 can have circumferential recesses which correspond to the protrusions 18a, 18b, 18c and which could receive the protrusions 18a, 18b, 18c in portions. The circumferential faces of the two sealing and guiding units 6 (sealing collars) are preferably planar (smooth), configured without recesses, wherein the protrusions 18a, 18b, 18c push into the circumferential wall such that radial plunging of the protrusions 18a, 18b, 18c into the sealing and guiding unit 6 results. A hybrid version having circumferential recesses in the sealing and guiding unit 6 is likewise conceivable, said circumferential recesses in terms of the radial extent thereof being smaller than the protrusions 18a, 18b, 18c such that plunging and pushing is combined. Independently of the type of the afore-described embodiment, the protrusions 18a, 18b, 18c are in engagement so as to engage axially behind the sealing and guiding unit 6.

[0046] The protrusions 18a, 18b, 18c, when viewed in the direction of an axial force F.sub.A resulting from the actuating pressure in the pressurized chamber 11, are of dissimilar sizes, wherein the first protrusion 18c which is disposed so as to be most remote from the first region 14 is larger than the second protrusion 18b which is larger than the smallest protrusion 18a which is disposed so as to be closest to the first region 14. The protrusions 18a, 18b, 18c are thus stepped, or disposed so as to decrease in size in the direction of the axial force F.sub.A, respectively (see FIG. 2). The sealing and guiding unit 6 by way of end face portions 22 of the protrusions 18a, 18b, 18c is thus secured against displacement in the axial direction relative to the external shell face 4 of the actuating piston 1, only one end face portion of the largest protrusion 18c being provided with a reference sign in this illustration.

[0047] A detailed illustration of the circumferential recess 8 is shown in FIG. 3. The first region 14 of each circumferential recess 8 of the actuating piston 1 has a guide region 20 on which the sealing and guiding unit 6 bears. In contrast to the protrusions 18a, 18b, 18c in the second region 16, there is no engagement or any undercutting between the guide region 20 and the sealing and guiding unit 6. On account of the guide region 20 which is large in terms of area, transverse forces F.sub.Q which by way of the sealing and guiding unit 6 act on the actuating piston 1 can be substantially better absorbed and distributed than is the case in the solutions known from the prior art.

[0048] The guide region 20 has a radial extent d, hereunder also referred to as the height d, which is substantially less than the axial extent a, hereunder also referred to as the length a. A space 40 which is delimited by an end face 36 of the circumferential recess 8, on the one hand, and is delimited by the guide region 20 and circumferentially by the base 34, on the other hand, is configured in the region of the end portion 26. A corresponding space 41 is configured in a further end portion 28, said space 41 being delimited by an end face 38, on the one hand, and delimited by the protrusion 18c and circumferentially by the base 34, on the other hand. The protrusions 18a, 18b, 18c as well as the guide region 20 extend from the base 34 in the radial direction.

[0049] The radial extent D.sub.a of the smallest protrusion 18a is larger than the radial extent d of the contact area formed by the guide region 20 and larger than the axial extent b of the protrusions 18a, 18b, 18c. The radial extent D.sub.c is larger than the radial extent D.sub.b and the latter is larger than the radial extent D.sub.a. The end face portions 22 which are configured on the protrusions 18a, 18b, 18c engage axially behind portions of the sealing and guiding unit 6 not illustrated here. These end face portions 22 absorb the axial force F.sub.A acting on the sealing and guiding unit 6 and by way of the protrusions 18a, 18b, 18c direct said axial force F.sub.A into the circumferential recess 8 and thus into the actuating piston 1.

[0050] The spaces 40, 41 in conjunction with the assigned sealing and guiding unit 6 configure radial gaps. Spaces are also configured between the guide region 20 and the protrusions 18a, 18b, 18c, as well as between the protrusions 18a, 18b, 18c. According to FIG. 2, the sealing and guiding unit 6 correspondingly does not bear on the base 34 of the circumferential recess 8. The internal stresses in the material of the sealing and guiding unit 6 draw the sealing and guiding unit 6 into the spaces 40, 41 configured in the region of the end portions 24, 26. The sealing and guiding unit 6 in the region of the end portions 24, 26 then configures in each case one chamfer 30, 32, said chamfers 30, 32 facilitating the configuration of a lubricating wedge in the case of the moving actuating piston 1. Moreover, a radial deformation of the sealing and guiding unit 6 which has effects which improve the sealing is moreover caused on account of the impingement of the sealing and guiding unit 6 with the axial force F.sub.A resulting from the actuating pressure.

[0051] Disclosed is an actuating piston for a hydrostatic adjustment installation having at least one sealing and guiding unit which is inserted into a circumferential recess of an actuating piston, said circumferential recess being composed of two regions, and has the effect of improving the guiding and sealing of the actuating piston. Furthermore disclosed is an adjustment installation which is configured having an actuating piston of this type.

LIST OF REFERENCE SIGNS

[0052] 1a Actuating cylinder

[0053] 1 Actuating piston

[0054] 2 Hydrostatic adjustment installation

[0055] 3 Main portion of the actuating cylinder

[0056] 4 External shell face

[0057] 5 Spring pack

[0058] 6 Sealing and guiding unit

[0059] 7 Pin

[0060] 8 Circumferential recess

[0061] 9 Adjustment pin

[0062] 10 Cover of the actuating cylinder

[0063] 11 Pressurized chamber

[0064] 12 Gap

[0065] 13 Support disk

[0066] 14 First region

[0067] 15 Support disk

[0068] 16 Second region

[0069] 17 Ventilation bore

[0070] 18 Protrusion

[0071] 19 Longitudinal axis

[0072] 20 Guide region

[0073] 21 Further pressurized chamber

[0074] 22 End face portion

[0075] 24 Internal shell face

[0076] 26 End portion

[0077] 28 End portion

[0078] 30 Chamfer

[0079] 32 Chamfer

[0080] 34 Base

[0081] 36 End face

[0082] 38 End face

[0083] 40 Chamber

[0084] 41 Chamber

[0085] F.sub.A Axial force

[0086] F.sub.Q Transverse force

[0087] a Length/axial extent of the guide region 20

[0088] b Length/axial extent of the protrusion

[0089] d Height/radial extent of the guide region 20

[0090] D Height/radial extent of the protrusion