EP2813712B1 - Piston unit of a plunger cylinder - Google Patents

Description

The invention relates to a piston unit for a plunger cylinder with a piston rod and a guide piston

Plunger cylinders, also called plunger cylinders, with corresponding piston units are generally known from the prior art. The piston units generally have a piston rod and a piston, wherein the piston rod acts as a plunger and the piston serves the axial guidance and is therefore also referred to as a guide piston.

Both components are preferably present as two separate components. In order to provide the necessary connection between the guide piston and the piston rod, according to the prior art, the guide piston is pressed onto the piston rod, for example, and / or welded to the piston rod.

The disadvantages of such a connection between the guide piston and the piston rod are, in particular, the additional work required to provide the connection and its unsolvability. Thus, in the event of damage to the guide piston or the piston rod or when a wear limit of the guide piston is reached, it is usually necessary to renew the entire piston unit, which in turn leads to increased repair and maintenance costs.

To avoid these disadvantages, solutions are also known from the prior art, in which the guide piston of a piston unit is formed by two separate half-shells, which are arranged at the desired position of the piston rod before inserting the piston unit into the plunger cylinder.

Such a solution is for example from publication DE 94 15 543 U1 known.

Here, two half-shell-shaped support segments are arranged on the piston rod, which are to ensure the leadership of the piston rod in the described hydraulic cylinder and which form the working piston area. By using the half-shells a particularly simple and fast assembly and disassembly of the working piston area should be provided. The solution disclosed here provides that the half-shells fixed to the insertion of the piston rod with the working piston area in the cylinder tube of the hydraulic cylinder in their position and must be secured against unwanted release of the piston rod.

This implies that appropriate devices or personnel must be provided for securing the half-shells until the piston rod is inserted into the cylinder tube, which in turn increases the provisioning costs for such a hydraulic cylinder. The publication DE 10 2011 009 365 A1 discloses a pressure cylinder with a cylinder tube, a longitudinally displaceably arranged in the cylinder tube piston, wherein the piston is provided with a piston guide means for guiding the piston in the radial direction in the cylinder tube and wherein the piston is provided with an extension movement of the piston limiting stop means.

On the piston a receiving groove extending in the circumferential direction is formed, wherein in the receiving groove consisting of two half-shells piston ring device is installed without tools, which takes over the function of the stopper and / or the piston guide device.

The object of the present invention is to provide, while avoiding the disadvantages of the prior art, a piston unit of a plunger cylinder, which can be made particularly simple and inexpensive and which allows cost-effective maintenance.

It is another object of the invention to provide a plunger cylinder with such a piston unit.

The object is achieved with respect to the piston unit by the features listed in claim 1 and with respect to the plunger cylinder by the features listed in claim 4. Preferred developments emerge from the respective subclaims.

A piston unit according to the invention of a plunger cylinder has a piston rod with a cylinder bottom side end portion and a guide side end portion.

The terms cylinder bottom side and guide side in this context represent position information and serve to describe positional relationships of components of the piston unit. They refer to the cylinder base and guide, which constitute components of the plunger cylinder and which are connected to a cylinder tube of the plunger cylinder. The cylinder bottom side end portion of the piston rod is facing the cylinder bottom in the correct installation position, while the guide-side end portion of the piston rod is arranged opposite in the direction of the guide.

The guide in this context forms the element which guides the piston rod inside the plunger cylinder.

According to the invention, the piston unit is characterized in that the piston rod in the region of the cylinder bottom end section has a circumferential, concave receiving contour.

The receiving contour itself in turn has an outer wall on the cylinder bottom side, which encloses an acute angle with the longitudinal axis of the piston rod.

The receiving contour can be provided in a simple manner, for example by machining the piston rod, in particular by turning.

The receiving contour preferably also has on the guide side an outer wall, which encloses an acute angle with the longitudinal axis of the piston rod, so that both outer walls together form a pointed throat.

For the embodiment of the guide piston described below and its interaction with the piston rod, the cylinder bottom side outer wall of the receiving contour is relevant.

The piston unit according to the invention has a guide piston through which the piston unit, when used in a plunger cylinder, in is guided to the cylinder tube. The guide piston is formed according to the invention by a first and a second half-shell, wherein the half-shells are arranged on the piston rod, that the half-shells embrace the piston rod in each case partially.

The piston unit is characterized in that the half shells of the guide piston rest with their inner circumferential surfaces on the outer circumferential surface of the piston rod and thus a positive connection between the half shells and the piston rod is provided by which the position of the half shells relative to the piston rod is fixed in the radial direction.

The half-shells have, as a particular advantage, mutually corresponding end regions.

Corresponding to one another means that, in the end position, the end regions of the first half-shell substantially adjoin the end regions of the second half-shell, whereby an overflow channel is provided between the piston chamber and the piston rod chamber. The corresponding end regions may preferably be formed as bevel cuts. The term end position refers to the arrangement in the assembled state.

Depending on the shape of the end regions, it may be brought about as a particular advantage that the half shells can be formed identically and thus no half shells with different end regions have to be provided. The provision costs for the half-shells and thus for the entire piston unit can thus be kept low.

The end regions of the half-shells are further designed such that the end regions of the first half-shell have a Umgreifungsversatz to the respective opposite end regions of the second half-shell. This means that the respectively adjoining end portions of the half-shells overhang each other in sections.

In addition, according to the invention, the half shells each have a circumferential engagement section with an inner engagement contour, wherein the respective engagement section forms the guide-side boundary of the associated half shell and wherein the engagement section is guided into the respective end region of the associated half shell.

The engagement contour is retracted relative to the inner circumferential surface of the respectively associated half shell, which means that the radius described by the engagement contour is smaller than the radius described by the inner circumferential surface of the associated half shell. In other words, the engagement portion preferably constitutes an inwardly angled region of the half shell.

The engagement contour of the respective half-shell is according to the invention designed so that it has an inner wall and that this engages, in particular in an end position of the respective half-shell on the piston rod in the receiving contour of the piston rod.

During the engagement of the engagement contour in the receiving contour, the inner wall of the engagement contour corresponds to the outer wall of the receiving contour, so that in the end position of the half shells on the piston rod a positive engagement of the engagement contour on the receiving contour is provided.

The positive engagement of the engagement contour on the outer contour causes a special technological advantage, especially in a load on the piston unit by a pressurized hydraulic medium, a reliable axial position fixing the half shells on the piston rod and a particularly uniform and optimized power transmission from the respective half-shell in the piston rod. This is particularly relevant when the piston unit is fully extended and the axial thrust needs to be absorbed by the guide.

Furthermore, the piston unit according to the invention is characterized in that each half-shell, by means of its engagement contour in a first end region and its, the engagement contour diagonally opposite, section of a second end portion, an angle greater than 180 ° and thus engages around the piston rod.

Another feature of the technical solution is that the encompassing of the piston rod by the half-shells by their pivoting about one, between the respective end regions of the associated half-shell forming, axle is available.

The particular advantage that the encompassing of the piston rod can be provided by the half-shells by pivoting the half-shells to one, forming between the end regions of the respective half-shell, axis is made possible by the described special geometries of receiving contour and engaging portion. According to the invention it is provided that the axis about which the pivoting of the half-shells, during the pivoting operation in its position is displaceable.

Expressed in simple terms, the half-shells can thus first be attached laterally to the piston rod by means of a receiving contour and engagement section and thus be pre-positioned in a simple manner; they can then be pivoted from the cylinder bottom side end portion of the piston rod until reaching the end position.

In order to enable the advantageous pivoting of the half-shells during their assembly to the piston rod, the respective end portions and engaging portions are inventively designed so that the half shells can be positioned on the piston rod such that only one contact point between the engagement contour and the Recording contour and between the respective, the engagement contour axially opposite, section of the associated end portion and the outer circumferential surface of the piston rod adjusts.

After the correct positioning of the half-shells on the piston rod, they are pivotable about the respective axis forming between the corresponding engagement contour and this diagonally opposite portion of the second end portion such that the engagement contour of the respective half-shell slides completely into the receiving contour of the piston rod. At the same time, the inner circumferential surfaces of the half-shells to the outer circumferential surface of the piston rod, so that forms a positive connection between the half-shells, both in the region of the engagement contours and in the region of the inner circumferential surfaces, and the piston rod.

The particular technological advantages of the assembly process made possible by the inventive design of the half shells and the receiving contour are, in particular, that on the one hand the half shells can be mounted on the piston rod with surprisingly little effort and thus without the use of a force applying assembly tool and that on the other during Pivoting the half shells only minimal elastic deformation of the half shells occur. The required elastic deformations of the half-shells are substantially lower than during an assembly movement, as they would be carried out without the interaction of inventive recording and engagement contour.

Especially due to the low elastic deformations, it is thus possible particularly advantageously to also use comparatively inelastic materials, for example from powder metallurgy for the half shells, or to avoid damage to the surfaces of half shells and piston rod during assembly.

In a particularly advantageous embodiment of the invention, the receiving contour of the piston rod on the guide side an outer wall, which includes an acute angle with the longitudinal axis of the piston rod. By virtue of the guide-side outer wall, the pivoting of the half-shells on the piston rod is optimized as a further advantage in that a sufficient free space is ensured between the engagement section and the guide-side outer wall of the receiving contour, which does not hinder a pivoted position of the half-shells at the beginning and during the assembly process. This ensures that the half-shells can be guided at least in sections in the region of the engagement contours in the receiving contour in their respective end position. In addition, an undesirable tilting of the half-shells during assembly on the piston rod can be effectively prevented. In addition, it can be dispensed with as far as possible in the complicated manner required by the prior art, the half shells during assembly.

In a preferred development of the piston unit, the end regions of the half shells are designed as oblique cuts.

In this way, with the least possible processing, the necessary for the invention encompassing the piston rod, embodiments of the end portions and the engagement portions, which provide only one support point of the end portion, or the engagement contour on the piston rod, are provided.

In addition, an advantageous variant of the piston unit is characterized in that the end portions of the first half-shell are arranged spaced from the respective opposite end portions of the second half-shell on the piston rod, wherein an overflow between the half-shells can be provided by the spacing.

In particular, in the present embodiment of the piston unit with a guide piston, which rests against the inner wall of the cylinder tube of the plunger cylinder, such an overflow channel is necessary to allow the hydraulic fluid to flow between piston chamber and piston rod chamber.

By providing the overflow channel by the spacing of the half shells from each other can thus be dispensed with an additional overflow and the associated expenses.

In addition, with an embodiment of the end regions of the half-shells as oblique cuts according to claim 2, the overflow channel having the desired width can already be provided by means of the cutting width of the oblique cuts without additional measures.

A plunger cylinder according to the invention has a cylinder tube, a cylinder bottom and a guide and is characterized in that it has a piston unit according to one of claims 1 to 3.

The piston unit is guided in a use of the plunger cylinder in the guide and additionally by means of the guide piston in the cylinder tube. At the same time, the guide and the cylinder bottom constitute the respective closure parts of the plunger cylinder, by which an escape of a hydraulic medium from the cylinder tube is prevented.

The particular advantages of a plunger cylinder according to the invention are in particular in the above-mentioned, simple and inexpensive provision of the piston unit with the guide piston and, in the use of the plunger cylinder, in the optimized power transmission between the guide piston and the piston rod due to the engagement and concerns of the half shells in or on the receiving contour of the piston rod. Furthermore, an overflow channel between the piston chamber and piston rod space is provided by the arrangement of the half shells without additional means.

A preferred development of the plunger cylinder provides that the guide has a conical seat on its side facing the guide piston of the piston unit.

The conical seat according to the invention is designed so that it corresponds with an outer wall of the engagement portion and thus forms an optimal end stop for the guide piston and thus for the piston unit. The corresponding design makes it possible to avoid any, uneven force and local force peaks in the guide piston upon reaching the end stop, which in particular damage to the guide piston can be prevented.

Fig. 1

Kolbeneinheit

Fig. 2

Detailansicht Kolbeneinheit mit erster Halbschale

Fig. 3

Detailansicht Kolbeneinheit mit erster Halbschale und aufgesetzter zweiter Halbschale

Fig. 4

Detailansicht Kolbeneinheit mit erster Halbschale und eingeschwenkter zweiter Halbschale

Fig. 5a

Seitenansicht zweite Halbschale

Fig. 5b

perspektivische Ansicht Halbschalen

Fig. 6

Plungerzylinder

näher erläutert.The invention will be described as an embodiment with reference to

Fig. 1

piston unit

Fig. 2

Detail view Piston unit with first half shell

Fig. 3

Detail view Piston unit with first half shell and attached second half shell

Fig. 4

Detail view Piston unit with first half shell and pivoted-in second half shell

Fig. 5a

Side view second half shell

Fig. 5b

perspective view half shells

Fig. 6

plunger

explained in more detail.

Fig. 1 shows a piston unit 1 according to the invention of a plunger cylinder in an overall view.

The piston unit has a piston rod 3 and a guide piston 4, wherein the guide piston 4 is arranged on a cylinder bottom side end portion of the piston rod. The term cylinder side is derived in this context from the, in Fig. 6 shown cylinder bottom 19 of the plunger cylinder 2 and in this case represents only a direction or position information.

The guide piston will, as in Fig. 1 illustrated, formed by a first half-shell 5 and a second half-shell 6, which are arranged on the piston rod 3 and which thereby engage in sections in a circumferential, concave receiving contour 7 of the piston rod 3.

Fig. 2 shows a detailed view of the piston unit 1 according to the invention, wherein in the present case only the first half-shell 5 is shown in its end position on the piston rod 3.

Of the Fig. 2 It can also be seen that the receiving contour 7 of the piston rod 3 on the cylinder bottom side has an outer wall 8 which encloses an acute angle α (alpha) with the longitudinal axis of the piston rod 3.

The receiving contour 7 is generated in the present embodiment by means of milling, wherein the receiving contour 7 is formed symmetrically in the vertical direction to simplify the milling process.

Furthermore, the first half-shell has a first end region 9 and a second end region 10, the end regions 9 and 10 being provided in each case by an oblique cut, and wherein, on the basis of the selected illustration in FIG Fig. 2 , only the front end portion 9 is visible.

Fig. 3 also shows a detailed view of the piston unit 1 according to the invention, wherein in the present case additionally the second half-shell 6 is shown in an assembly position before reaching its end position on the piston rod 3.

The second half-shell 6 also has two end regions 11 and 12, whereby only in this case, due to the selected representation, only the front, first end region 11 is visible.

In addition, both half-shells 5 and 6 have an engagement portion, each with an engagement contour 13, and 14, respectively.

As a particular technological advantage of the invention, the half-shells 5 and 6 are formed such that each half-shell 5, 6, by means of their associated engagement contour 13, 14, in the first end portion 9, 11 and one, the respective engagement contour 13, 14 axially opposite, Section in the second end portion 10, 12 (not shown), an angle greater than 180 ° includes. As a result, a recapture of the piston rod 3 is provided by the half-shells 5 and 6, through which a particularly advantageous manner during assembly of the piston unit according to the invention, an unwanted release of the half-shells 5 and 6 is prevented by the piston rod 3.

It has been shown that due to the inventive design of the half shells 5 and 6 and their interaction with the receiving contour 7, as a further technological advantage of the piston unit 1 a very simple assembly of the half shells 5 and 6 on the piston rod 3 is made possible, which also with a small force and can be done with comparatively very small, elastic deformations of the half shells 5 and 6.

• Zuerst wird die zweite Halbschale 6 schräg auf der Kolbenstange 3 positioniert, sodass der zylinderbodenseitige Eckpunkt des ersten Endabschnitts 11 auf der Außenmantelfläche der Kolbenstange anliegt. Gleichzeitig liegt der führungsseitige Eckpunkt des zweiten Endbereichs 12 (nicht dargestellt) im Bereich der Aufnahmekontur 7 an der Kolbenstange 3 an.

The assembly of the half-shells 5 and 6 is carried out in the present case by hand in the following manner (illustrated by the representation of the second half-shell 6 in Fig. 3 and 4 ):

• First, the second half-shell 6 is positioned obliquely on the piston rod 3, so that the bottom edge of the cylinder-side corner of the first end portion 11 rests on the outer circumferential surface of the piston rod. At the same time, the guide-side corner point of the second end region 12 (not shown) rests against the piston rod 3 in the region of the receiving contour 7.

After positioning the second half-shell 6 on the piston rod 3, the second half-shell 6 is pivoted about an axis (not shown) forming between the cylinder-bottom side corner of the first end portion 11 and the leading-side corner of the second end portion 12 (not shown). The pivoting movement is present in Fig. 3 illustrated by the curved arrow.

During the pivoting, in particular, the engagement portion of the second half-shell 6 slides with the engagement contour 14 in the receiving contour 7, which in Fig. 3 is illustrated by the horizontal arrow.

Fig. 4 shows the end position of the second half-shell 6 on the piston rod 3. In the end position according to the invention adjusts a positive connection between the half-shells 5 and 6 and the outer circumferential surface of the piston rod 3, wherein the positive connection is representative illustrated by the second half-shell 6.

The positive connection is characterized in particular in that the inner wall 16 of the engagement contour 14 of the second half-shell 6 rests against the outer wall 8 of the receiving contour 7. In addition, the inner circumferential surface of the second half-shell 6 abuts against the outer contour surface of the piston rod 3 outside the receiving contour 7.

By virtue of the inventively provided, positive connection of the half-shells 5 and 6 with the piston rod 3, it is possible as an additional advantage that the half-shells 5 and 6, when using the piston unit in a plunger cylinder, in its position against both a radial and against a axial position change relative to the piston rod 3 are secured.

In addition, a uniform and optimal transmission of forces occurring from the half-shells 5 and 6 is ensured in the piston rod 3 by the engagement portions 13, 14 of the half-shells 5 and 6.

Again Fig. 4 can also be seen, the half-shells 5 and 6 are arranged in their end position on the piston rod 3 spaced from each other, that between the opposite end portions 9 and 11, or 10 and 12 (not shown) of the half-shells 5 and 6 respectively Overflow 17 forms.

Via the overflow channel 17, during the use of the piston unit according to the invention in a plunger cylinder, a pressure medium (not shown) can flow over from one working space into another working space.

A second half-shell 6 according to the invention is shown in FIG Fig. 5a shown in a side view.

This shows Fig. 5a in particular, the first end region 11 and the second end region 12 of the second half-shell 6, wherein on the cylinder bottom side end of the first end portion 11, an outbreak is shown.

In addition, shows Fig. 5b a view of the mutually positioned first and second half-shell 5 and 6 from a side-leadership perspective. Fig. 6 shows a plunger cylinder 2 according to the invention with a cylinder tube 18, a cylinder bottom 19 and a guide 20th

In addition, the plunger cylinder 2 has a pressure medium connection 23, via which a hydraulic pressure medium can be introduced into the cylinder tube 18, or can be discharged from the cylinder tube 18.

The plunger cylinder 2 according to the invention comprises a piston unit 1 according to one of claims 1 to 3, wherein the piston unit 1 is guided in the region of the piston rod 3 in the guide 20 and in the region of the guide piston 4 through the inner circumferential surface of the cylinder tube 18.

A particular technological advantage of the plunger cylinder 2 is in the present case in connection with its manufacture and in particular in connection with the pre-assembly of the piston unit 1. Due to the provision of the encompassing of the piston rod 3 by the half-shells 5 and 6 of the guide piston 4, an inadvertent release of the guide piston 4th from the piston rod 3, before inserting the piston unit 1 in the cylinder tube 18 of the plunger cylinder 2, effectively prevented.

In a preferred embodiment, the guide 20 of the plunger cylinder 2, on the guide piston 4 of the piston unit 1 side facing, a conical seat 21, which with the, in the Fig. 2 to 4 shown, engaging portions of the half-shells 5 and 6 corresponds.

The guide 20 with the conical seat 21 serves in the present case as an end stop for the piston unit 1, by which the maximum extension path of the piston unit 1 is limited in the cylinder tube 18.

By the conical seat 21, an optimal concern of the guide piston 4 is secured to the guide 20, whereby occurring axial forces are absorbed by the guide 20 which is connected to the cylinder tube 18.

Used reference signs

1

piston unit

2

plunger

3

piston rod

4

guide piston

5

first half shell

6

second half shell

7

Up Silhouette

8th

Outer wall of the receiving contour

9

first end region of the first half shell

10

second end region of the first half shell

11

first end portion of the second half-shell

12

second end region of the second half shell

13

Engagement contour of the first half shell

14

Engagement contour of the second half shell

15

Inner wall of the engagement contour of the first half shell

16

Inner wall of the engagement contour of the second half-shell

17

overflow

18

cylinder tube

19

cylinder base

20

guide

21

conical seat

22

sealing element

23

Pressure medium connection

Claims (5)

1. A piston unit (1) for a plunger cylinder (2) comprising a piston rod (3) with an end section at the cylinder bottom side and an end section at the guide side, and comprising a guide piston (4) which is formed by a first half shell (5) and by a second half shell (6), wherein the half shells (5, 6) encompass the piston rod (3) at least in sections,
   characterized in
   that the piston rod (3) has a circumferential, concave receiving contour (7) in the area of the end section at the cylinder bottom side, wherein the receiving contour (7) has an outer wall (8) at the cylinder bottom side and wherein the outer wall (8) encloses an acute angle α (alpha) with the longitudinal axis of the piston rod (3), and that the inner jacket surface of each half shell (5, 6) rests on an outer jacket surface of the piston rod (3), and that the half shells (5, 6) have end sections (9, 10 and 11, 12) corresponding to each other, wherein the end sections (9, 10) of the first half shell (5) have an encompassing offset to the corresponding opposite end sections (11, 12) of the second half shell (6), and that each half shell (5, 6) is provided with an engagement section with an inside engagement contour (13, 14), wherein the corresponding engagement section constitutes the guide-side boundary of the allocated half shell (5, 6) and wherein the corresponding engagement contour (13, 14) is retracted relative to the inner jacket surface of the appropriate half shell (5, 6) and wherein the corresponding engagement contour (13, 14) of the appropriated half shell (5, 6) engages in the receiving contour (7) of the piston rod (3) and wherein each engagement contour (13, 14) has an inner wall (15, 16), wherein the corresponding inner wall (15, 16) corresponds to the cylinder-bottom-side outer wall (8) of the receiving contour (7), and that each half shell (5, 6) encloses an encompassing angle greater than 180° by the appropriate engagement contour (13, 14), in its first end section (9, 10) and by a section, axially opposite to the corresponding engagement contour (13, 14), in its second end section (10, 12).
2. The piston rod according to claim 1,
   characterized in
   that the end sections (9, 10, 11, 12) of the corresponding half shell (5, 6) are designed as bevel cuts.
3. The piston rod according to claim 1 or 2,
   characterized in
   that the end sections (9, 10) of the first half shell (5) are arranged at a distance to the corresponding opposite end sections (11, 12) of the second half shell (6) on the piston rod, wherein an overflow channel (17) between the half shells (5, 6) can be provided by the distance.
4. A plunger cylinder (2) with a cylinder rod (18), a cylinder bottom (19) and a guide (20),
   characterized in
   that it comprises a piston unit (1) according to one of the claims 1 to 3, wherein the piston unit (1) is received in the cylinder rod (18) and guided in the guide (20) and, by means of the guide piston (4), at the inner wall of the cylinder rod (18).
5. The plunger cylinder according to claim 4,
   characterized in
   that the guide has a conical fit (21) on its side facing the guide piston (4), and said fit corresponds to an outer wall (22, 23) of the appropriate engagement section of the half shells (5, 6) and is used to provide/can function as an end stop of the piston unit (1) in the cylinder rod (18).

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