EP3178581B1 - High frequency hydraulic cylinder - Google Patents

Description

The invention relates to a high-frequency cylinder with an extremely fast and yet reliable and very compact high-frequency drive for highest working speeds, for example for high-speed cutting (HGSS) or forging.

From the Godfather literature Schnellhubzylinder called hydraulic cylinders are known, which are designed for the generation of rapid rapid movements in hydraulic presses, for example, known from the DE102005047995B4 . DE 19642635A1 or DE 2127605C3 ,

Fast rapid movements are for example desired in idle strokes of machines such as presses and are referred to as quick-stroke or rapid traverse cylinder. They move the press ram in the idle stroke much faster than it would be possible with the area far larger working cylinder. The oil of the working cylinder is sucked in only with negative pressure. They have the same structure as usual working cylinders. Furthermore, hydraulic cylinders are also referred to as rapid traverse or quick-lift cylinders when conventional hydraulic cylinders receive an oil feed via storage or servo valves ( DE102007010426B4 ).

By reducing the mass of the moving cylinder parts, for example by using fiber materials, the dynamics can also be improved ( DE 3215795A1 ). Such known cylinders can be used for example in test benches, where it is required to accelerate a test object to a higher speed. Another field of application is the rapid supply and removal of parts in production processes.

For certain applications, however, much higher speeds are desired with high cylinder forces. Here come various processes of manufacturing processing of products in question, in which highest speeds are desired. This applies, for example, to the shear cutting of sheet metal or bar stock, where at high shear rates the process heat remains in the immediate shear area and, due to the higher shear temperature, a much better cut surface quality can be achieved. Equally true is the advantage of highest working speeds during forging. In hot forging machines, efforts are made to achieve high speeds to minimize the contact time of the mold halves with the hot workpiece.

In the DE 42 33 115 a device is described in which a coupling of the freely movable within a cylinder chamber piston is realized in an end position by means of the pressure control of a control room. However, this cylinder is not able to achieve the desired high speeds, in extreme cases 200 km / h. Likewise, no large forces can be applied over a longer distance. There are currently no hydraulic cylinders in use, which can be realized in such a simple way such high speeds at high forces.

In the patent DE 2007018066 is a device for impulse hydroforming specified. The operation of the working piston takes place in this type by ignition of an explosive mixture. However, such approaches have always proved problematic, such as wear and safety problems.

In the DE 10 2012 019 386 A1 is a device specified in which biased springs press on toggle that is slightly above the extended position. By a mechanical movement, the toggle lever are brought out of the extended position and move abruptly down due to the existing spring preload. The disadvantage here is that in particular The use of a large area on the part of the limited in their power springs requires a lot of space. The required traverse for setting up the springs continues to cause a due to their own inertia
significant reduction of the actually desired high speed for the working stroke.

The DE 19602390 A1 relates to a working cylinder with a piston and a cylinder whose inner diameter is greater than the maximum piston diameter. In order to avoid flow losses of the cylinder during the idle stroke of the piston and to make coupling of the piston with the cylinder for the working stroke faster, more wear-resistant and more reliable, the cylinder has an annular component with which the piston interacts during the working stroke, in that a functional space is formed between the piston, the annular component and the cylinder, which is sealed off from the remaining cylinder space and whose pressure can be controlled via a control valve.

The object of the present invention is therefore to provide an extremely fast and yet reliable and very compact high-frequency drive with the highest operating speeds, for example for high-speed cutting (HGSS) or forging.

This object is achieved by the invention according to claim 1. Advantageous and expedient refinements can be found in the subclaims.

In this case, a hydraulic cylinder is designed so that the piston can extend at extremely high speeds. At the same time, the return stroke of the piston should take place in the shortest possible time in order to enable the highest number of deliveries.

The high-frequency cylinder comprises a piston and a cylinder tube whose inner diameter is larger than the maximum diameter of the piston, the piston being internally hydraulically locked and disengageable to a control ring by the switching of valves, the clutched state hydraulically released for the purpose of extremely fast extension of the piston is and at the same time internally comprises a piston enclosing the accumulator piston and from the storage space pressure accumulator whose energy is released during rapid extension of the piston practically without flow losses of hydraulic lines to the piston.

An accumulator piston has an externally applied on its upper side with gas pressure outer annular storage area and an inner annular guide approach, which is acted upon at its top not with gas pressure but with the pressure of the return control chamber and is acted upon on its underside with the pressure of the cylinder chamber and at his Inner diameter forms a guide surface for the piston.

On the piston, a differential surface is formed, which is permanently subjected to oil pressure. The ratio of the area of the differential surface to the upper surface of the guide lug behaves as the surface of the lower piston portion with the diameter D1 to the effective area of the accumulator piston of D4 and D1.

During extension of the piston, the volume of the return control chamber remains approximately constant, with the return control chamber being connected to a reservoir.

The hydraulic control is carried out by means of a rotary valve, in whose rotor and stator oil connections for pump and tank are introduced. The rotor is mechanically coupled to a workpiece feed drive.

The hydraulic coupling of the piston can be achieved by frontal pressure relief of the piston by means of a, in particular metallic, Control ring in the retracted state of the piston or by immersing the piston in a recess in the bottom element in subsequent pressure relief of the lower end face of the piston can be realized.

The piston dips to the end of extension in the oil damping chamber on the accumulator piston or in a separate, located in front of the accumulator piston within an intermediate plate damping chamber. The piston seal is connected in front of a relief groove, which is connected to the tank during extension of the piston.

In an example calculation it is shown that stroke rates of 1000 rpm are possible and that a limitation mainly occurs through the switching times of valves. The usual number of deliveries of hydraulic presses are far exceeded. In a further embodiment with a special switching drive, the limitation is eliminated by switching times of valves for even higher stroke rates. The extremely fast extending piston can directly actuate a working element or serve as a drive for another drive, for example, designed for a hydraulic cylinder as a pressure booster.

Fig. 1 describes the design of the high-frequency cylinder according to the invention. In the initial state of the collar sits 5 of the piston 1 on the bottom element 26. The control ring 33 forms with the lower part of the collar 5 a sealing surface 34, which shields the pressure prevailing in the cylinder chamber 23 pressure against the control chamber 38. The control chamber 38 is relieved via the control valve 32 to tank. The control ring 33 is acted upon on its underside with the pressure prevailing in the cylinder chamber 23 pressure. On its upper side, it is partially relieved of pressure via a small paragraph to the control chamber 38 and the pressure drop across the sealing surface 34 between the cylinder chamber 23 and the control chamber 38. The upper annular surface of the collar 5 is fully loaded with the pressure prevailing in the cylinder chamber 23, while the pressure axial opposite, lower collar surface is only partially acted upon by the pressure prevailing in the cylinder chamber 23 pressure. The piston is locked.

In the space 21, the gas storage space formed between the parts 17 and 7, a gas, for example, nitrogen was introduced with the biasing pressure of 100 bar via the gas storage port 14 before the pressure buildup in the cylinder chamber 23. The accumulator piston 17 was seated on the spacer tube 24. As a result of a pressure buildup in the cylinder chamber 23 by oil supply via the oil port 29, for example to 300 bar, the accumulator piston 17 was moved upwards and reduces the volume of the gas storage space to 1/3.

Now, if the control chamber 38 is acted upon by the control valve 32 with pressure, the balance of power on the piston 1 with the collar 5 change abruptly. The pressurized surface on the underside of the piston 1 with the collar 5 is now larger than the pressurized surface at the top of the collar 5. The piston 1 dissolves and moves virtually unhindered upwards. It is accelerated with a force resulting from the diameter D2 of the upper piston section 2 and the pressure in the cylinder chamber 23.

Example: Diameter piston 30mm Length piston 350mm Average pressure 220 bar path 50mm → speed 28 m / sec, 100km / h path 10mm → speed 13 m / sec, 45km / h

On a way of 50mm, the piston reaches a speed of 28m / sec! On a way of 10mm, the piston reaches a speed of 13m / sec!

At a maximum speed of 28m / sec the average speed is 14m / sec. Thus, the piston for 50mm piston travel requires the time of almost 4msec! For the Dauerhubzahl are practically only the return stroke and the time to repressurization crucial. When cutting sheet metal at high speeds, it is endeavored to achieve a speed of at least 10 m / sec.

In this speed range, significant improvements in part quality can be achieved. This speed is already reached with the high frequency cylinder with an acceleration travel of 10mm!

When cutting sheet metal, the cost of the associated machine is largely to achieve the required maximum force. Presses are accounted for at purchase primarily by tonnage. With the high-frequency cylinder according to the invention, however, the working energy is specified during cutting. Thus, with a relatively small piston diameter, astonishing maximum forces due to the dynamic processes can be achieved.

example

Given is 1 .: Diameter of sheet metal cutting 100mm / sheet thickness: 7mm Break to: 3mm / linear force increase Overcoming strength: 300N / mm ^ 2 → maximum force approx. 670kN → energy approx. 1000Nm → A 67-ton press is required at least
Given is 2 .: D-piston 30mm Pressure 320 Bar piston stroke 50mm → Energy ample 1000Nm! The energy of a high-frequency cylinder with a 30mm piston and a stroke of 50mm is enough to replace a 670kN press!

For cutting a blank of 1000mm with a corresponding 6700kN press (W = 10.000Nm) it is sufficient to use the following high-frequency cylinder: D-bulb 80mm pressure 320 bar piston stroke 70mm → Energy plentiful 11,000Nm! The energy of a high-frequency cylinder with an 80 mm piston is sufficient to replace a 6700kN press (sheet metal cutting)!

Currently, high-strength sheets are entering production technology. When cutting high-strength and ultra-high-strength metal sheets, the advantage of the high-frequency cylinder is even more pronounced, since the forces increase strongly here, while at the same time breaking occurs earlier when cutting through.

Because of the high energy that builds up the piston during its acceleration, the piston should always reduce its energy externally in one operation. Should it happen due to an incorrect setting that no external energy reduction takes place, the collar 5 of the piston 1 enters the oil damping chamber 20. By entering into the formed on the oil damping chamber 20 slope energy of the piston is reduced there. The spring-back of the accumulator piston 17 in the direction of the gas storage space 21 supports the energy reduction.

As a rule, however, the collar 5 of the piston 1 comes to a standstill beforehand due to the external operation.

The piston 1 has an upper piston portion 2 and a lower piston portion 3. These form the differential area 4, via which the return stroke is realized by means of pressurization. When the piston is extended, oil is displaced through the differential surface 4 and must be able to flow with as little flow as possible, otherwise it would hinder the extension of the piston with the build-up of a flow pressure.

The build-up of a noticeable flow pressure is prevented by the fact that the stale oil in the return control chamber 8 can remain in place. This is realized by the accumulator piston 17 has a guide lug 18 and certain diameter ratios are met. The ratio of the speeds of piston 1 and accumulator piston 17 results from their surfaces. The following applies: $$\mathbf{v}\mathrm{-}\mathbf{piston}/\mathbf{v}\mathrm{-}\mathbf{accumulator\; piston}=\mathbf{A}\mathrm{-}\mathbf{accumulator\; piston}\left(\mathbf{D}4;\mathbf{<figure-callout\; id="1"\; label="D"\; filenames="imgf0001.png"\; state="\{\{state\}\}">D</figure-callout>}1\right)/\mathbf{A}\mathrm{-}<figure-callout\; id="1"\; label="\; piston\; D"\; filenames="imgf0001.png"\; state="\{\{state\}\}">\; </figure-callout>\mathbf{piston}\left(\mathbf{D}\right)\left(\mathbf{}1\right)$$

Assuming an effective area ratio accumulator piston / piston of 10, resulting in the piston 1, the tenfold speed compared to the accumulator piston 17th

Speicherkolben
dann wird die Verkleinerung des Rücksteuerraums 8 infolge des von der Differenzfläche 4 beim Ausfahren des Kolbens verdrängten Öls exakt kompensiert durch die Vergrößerung des Rücksteuerraums 8 infolge der Bewegung des Führungsansatzes 18 des Speicherkolbens 17 nach unten.If the differential area 4 and the effective area of the guide projection 18 continue to apply: $$\mathrm{A\; <figure-callout\; id="3"\; label="leadership\; approach\; D"\; filenames="imgf0001.png"\; state="\{\{state\}\}">leadership\; approach\; </figure-callout>}\left(\mathrm{D}\right)\left(\mathrm{}3;\mathrm{<figure-callout\; id="1"\; label="D"\; filenames="imgf0001.png"\; state="\{\{state\}\}">D</figure-callout>}1\right)/\mathrm{A\; <figure-callout\; id="2"\; label="differential\; area\; D"\; filenames="imgf0001.png"\; state="\{\{state\}\}">differential\; area\; </figure-callout>}\left(\mathrm{D}\right)\left(\mathrm{}2;\mathrm{<figure-callout\; id="1"\; label="D"\; filenames="imgf0001.png"\; state="\{\{state\}\}">D</figure-callout>}1\right)=\mathrm{v\; flask}/v$$

accumulator piston
then the reduction of the return control chamber 8 due to the displaced by the differential surface 4 during the extension of the piston oil is compensated exactly by the increase in the return control chamber 8 due to the movement of the guide extension 18 of the accumulator piston 17 down.

The return control chamber 8 is permanently pressurized. A small oil reservoir ensures that there is always pressure in the return control chamber 8. Smaller area deviations deviating from the optimum ratio can thus be compensated.

At the same time there is quickly enough oil available to be able to carry out the return stroke in the shortest possible time. From the control valve 32, the return stroke of the piston is initiated. By switching the control valve 32, the cylinder chamber 23 is now connected to the tank. The bottom of the piston 1 is depressurized except for the self-adjusting residual pressure due to flow. At the differential area 4 is permanently the pressure of the memory on the Oil storage port 13 on. The piston is moved back to its initial position until it touches down on the sealing surface 34 again.

For an exemplary diameter D1 of 30 and D2 of FIG. 28, the magnitude of the differential area 4 is 1 cm ³ . For 50mm Rückhubweg so about 5cm ³ oil of needed. With one liter of oil from the pump thus 200 return strokes can be realized, for 1000 strokes / min so you need an oil flow of 5L / min.

The pressure flowing from the connection 29 into the cylinder chamber 23, in conjunction with the springs 36, ensures the renewed coupling between the collar 5 of the piston 1 and the control ring 33 for the renewed production of the starting position.

The inflowing into the cylinder chamber 23 oil ensures the re-storage charging by the reduction of the gas storage space 21 due to displacement of the accumulator piston 17 upwards. With an upper piston diameter of 28 mm and a piston length of 50 mm pushed out of the cylinder, a required oil volume of about 31 cm ³ results. Together with the oil requirement for the return stroke of about 5cm ³ results in an oil consumption of 36cm ³ per stroke.

With one liter of oil from the pump thus approx. 28 strokes can be realized.

With a pump volume of 36L / min, 1000 strokes / min can thus be driven. The Hubzahleinschränkung comes then mainly due to the switching times of hydraulic valves. One solution to eliminate the switching times of hydraulic valves is in Fig. 2 specified.

Fig. 2 shows the fast and reliable control by means of a rotary valve. Such a valve is for example from the Scriptures DE 10 2012 024 642 A1 known. It is able to realize a valve control at highest frequencies up to 2000 / min.

With the rotary valve shown, a stator 40 and a rotor 39 are provided. In the stator 40 oil connections are introduced for pump and tank. The rotor 39 has the recesses a to d. These connect depending on the rotation angle of the rotor 39, the terminals 29 and 30 of the high-frequency cylinder with pump and tank according to the present rotation angle.

Fig. 2a and Fig. 2b represent in the rotary valve successively arranged cuts. The rotor may be mechanically coupled to the drive of a feed unit not shown via a direct shaft connection or a transmission. In this way it is ensured that the movement of the piston 1 runs absolutely synchronously with the feed at the highest stroke rates of the high-frequency cylinder.

LIST OF REFERENCE NUMBERS

1

piston

2

Upper piston section

3

Lower piston section

4

differential area

5

Federation

6

centering

7

control part

8th

Back control space

9

Upper piston guide

10

Memory piston guide

11

relief

12

piston seal

13

Oil storage terminal

14

Gas storage terminal

15

Drain port

16

thermowell

17

accumulator piston

18

leadership approach

19

gas seal

20

Oil damping space

21

Gas storage space

22

cylinder tube

23

cylinder space

24

spacer tube

25

cylinder seal

26

floor element

27

centering

28

ring groove

29

Oil connection cylinder room

30

Oil connection control room

31

floor seal

32

control valve

33

control ring

34

sealing surface

35

control seal

36

feather

37

retaining ring

38

control room

39

rotor

40

stator

41

Storage ring surface

Claims (8)

1. High-frequency cylinder having a piston (1) and a cylinder tube (22) whose inner diameter is larger than the maximum diameter of the piston (1), and a storage piston (17) having an outer storage ring surface (41) whose upper surface is acted upon by gas pressure,
   characterised in that
   the storage piston (17) has an internal annular guide extension (18) which is not acted upon on its upper surface by gas pressure but instead by pressure from a reverse control chamber (8) and on its lower surface by pressure from a cylinder chamber (23), and in which a guide surface for the piston (1) is present on the inside diameter.
2. High frequency cylinder according to claim 1,
   characterised in that
   the piston (1) has an upper piston section (2) and a lower piston section (3) which form a differential surface (4) and by which the return stroke of the piston (1) can be realised by applying pressure, the differential surface (4) being permanently subjected to oil pressure.
3. High frequency cylinder according to claims 1 and 2,
   characterised in that
   the volume of the return control chamber (8) remains approximately constant during the extension of the piston (1), and in that the return control chamber (8) can be connected to an accumulator.
4. Arrangement with a high-frequency cylinder according to claims 1 to 3, a rotation valve and a workpiece feed drive,
   characterised in that
   the high frequency cylinder is hydraulically controlled by the rotary valve, into whose rotor (39) and stator (40) are introduced oil connections for pump and tank, the rotor (39) being mechanically coupled to the workpiece feed drive.
5. Arrangement according to claim 4 or high frequency cylinder according to claims 1 to 3,
   characterised in that
   the hydraulic coupling of the piston (1) can be realised by relieving the pressure on the end face of the piston (1) by means of the high frequency cylinder's metal control ring (33) in the retracted state of the piston (1).
6. Arrangement as per claim 4 or high frequency cylinder as per claims 1 to 3 and 5,
   characterised in that
   the hydraulic coupling can be realised by immersing the piston (1) into a depression in a base element (26) of the high frequency cylinder with subsequent pressure relief of the lower end face of the piston (1).
7. Arrangement according to claim 4 or high frequency cylinder according to claims 1 to 3 and 5 to 6,
   characterised in that
   an inside-facing relief groove, which can be connected to the tank during the extension of the piston (1), is connected upstream of a piston seal (12).
8. Arrangement as per claim 4 or high frequency cylinder as per claims 1 to 3 and 5 to 7,
   characterised in that
   the piston (1) is immersed at the end of the extension into a separate damping space of the high frequency cylinder which is located in front of the storage piston (17) within an intermediate plate.

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