WO2010057559A1

WO2010057559A1 - Damper for damping the return stroke movement of an operating piston that can be traveled over by the plunger of a press

Info

Publication number: WO2010057559A1
Application number: PCT/EP2009/007615
Authority: WO
Inventors: Werner Kuttruf
Original assignee: Voith Patent Gmbh
Priority date: 2008-11-21
Filing date: 2009-10-24
Publication date: 2010-05-27
Also published as: DE102008058526A1; DE102008058526B4

Abstract

The invention relates to a damper for damping the return stroke movement of an operating piston that can be traveled over by the plunger of a press from an upper dead point OT to a lower dead point UT, wherein the operating piston is movably arranged in an operating cylinder and delimits a lower operating pressure chamber that can be filled with hydraulic fluid, said damper having a separating piston with which the lower side of the lower operating pressure chamber can be sealed against a hydraulic pressure chamber and that delimits a gas pressure chamber on the lower side turned away from the operating piston, wherein upon moving the operating piston from the OT toward the UT, hydraulic fluid is forced out of the lower operating pressure chamber into the hydraulic pressure chamber and the separating piston moves toward the lower end position and wherein the separating piston moves up after reaching a lower end position thereof and seals the lower operating pressure chamber dependent on the path.

Description

Damping device for damping the return stroke of a convertible from a plunger of a press working piston

description

The invention relates to a damping device for damping the return stroke movement of a ram of a press from a top dead center OT in a bottom dead center UT traversable working piston.

Such damping devices are previously known from the prior art in many ways and are also known as feather pillows or die cushion.

Various types of die cushion are previously known for example from DE 10 2006 058 630 Al and DE 37 37 967 C2.

The present invention has for its object to provide a damping device mentioned above, on the one hand has a comparatively simple structure and with the appropriate damping is still achievable.

The object of the invention is achieved by a

Damping device solved with the features of claim 1. The working piston is thus arranged movably in a working cylinder and limits a fillable with hydraulic fluid lower working pressure chamber. Furthermore, a separating piston is provided with which the lower side of the lower working pressure chamber can be closed with respect to a hydraulic pressure chamber. The separating piston delimits, on the lower side facing away from the working piston, a gas pressure space which can be filled with gas pressure. The damping device is designed so that when Moving the working piston from top dead center in the direction of bottom dead center hydraulic fluid is forced from the lower working pressure chamber in the hydraulic pressure chamber, whereby the separating piston moves towards the lower end position and thereby increases the gas pressure in the gas pressure chamber. Furthermore, the arrangement is such that the separating piston is moved after reaching the bottom dead center of the working piston from its lower end position due to the pressure prevailing in the gas pressure chamber gas pressure and the return stroke of the press ram up and thereby closes the lower working pressure chamber path-dependent. Due to the path-dependent closing a damped return stroke of the working piston is achieved. On the one hand, the pressure of the hydraulic fluid and, on the other hand, the gas pressure can always be monitored and controlled. The device comes with comparatively small amounts of hydraulic fluid and comparatively small gas pressure chamber. Overall, a very high reliability.

It is advantageous if Gasdruckeinstellmittel for adjusting the gas pressure and when Hydraulikfüßigkeitseinstellmittel provided for adjusting the Hydraulikfütigkeitsdrucks such that the gas pressure regardless of

Hydraulic fluid pressure is adjustable. In particular, by providing the separating the hydraulic pressure chamber and the gas pressure chamber separating piston can be changed via the adjustable working pressure in the gas pressure chamber, the bias of the damping device. For adjusting the gas pressure, in particular, a gas pressure regulating valve which can be connected to a gas pressure source can be provided. The working pressure is always controlled and monitored during operation of the damping device. In the rest position of the device, when no external forces act on the working piston, the working pressure in the gas pressure chamber is preferably greater than the base pressure in the hydraulic pressure chamber. This will ensures that the separating piston is moved to its upper end position.

According to the invention can be advantageously provided that at least one of the lower working pressure chamber leading to the hydraulic pressure chamber throttle opening is provided and that the separating piston in an intermediate position only the lower working pressure chamber and in its end position also closes the at least one throttle opening. In the return stroke of the working piston, this results in a two-stage damping. The fact that initially the working pressure chamber is closed when the throttle opening is still open, a first stage of the damping takes place. By the subsequent closing of the throttle opening, the damping takes place in a second stage. It is advantageous if the separating piston in the upward movement in the direction of the upper end position, the at least one throttle opening travels depending on the path. The separating piston can form a control edge, which reduces the open cross section of the throttle opening in its upward movement and ultimately closes.

In a further embodiment of the invention, it is advantageous if the working piston defines an upper working pressure space which can be filled with hydraulic fluid, wherein the upper working pressure space is connected to the hydraulic pressure space via passage openings. It is advantageous if the effective piston surface, which limits the upper working pressure chamber, is smaller than the effective piston surface, which limits the lower pressure chamber. This ensures that at constant pressure of the working piston is moved to its top dead center or remains in this top dead center.

According to the invention, it is conceivable that the hydraulic pressure chamber and the gas pressure chamber are in each case closed pressure chambers are formed. Elaborate hydraulic accumulator or gas pressure accumulator account for this.

In a particularly preferred embodiment of the invention, it is provided that the separating piston comprises a control piston biased by means of a spring element in the direction of the lower working pressure chamber, the outer diameter of which essentially corresponds to the inner diameter of the working cylinder and which engages in the working cylinder for closing the lower working pressure chamber. The diameter of the portion of the control piston, which faces the lower working pressure chamber, advantageously corresponds to the diameter of the side of the working piston, which also limits the lower working pressure chamber. The spring element can be designed as a helical spring, which is supported at one end on the separating piston and the other end on the control piston. Due to the provision of the spring element ensures that the control piston with respect to the separating piston assumes a predetermined position.

It is also advantageous if the at least one throttle opening is provided in the region of the lower end of the working cylinder and when the control piston in the upper end position of the separating piston closes the throttle opening. The control piston may provide a control edge, which is heading for the movement of the separating piston or the control piston up to the throttle opening.

According to the invention, it is also conceivable that, as the working piston moves from top dead center OT in the direction of bottom dead center UT, the control piston moves downward against the biasing force of the spring element due to the pressure increasing in the lower working pressure space and the throttle opening is thereby opened Hydraulic fluid from the lower working pressure chamber can flow into the upper working pressure chamber, and is moved on further movement of the working piston in the direction of bottom dead center of the control piston with separating piston down, so that the lower working pressure chamber is opened to the hydraulic pressure chamber. When moving the working piston from the top dead center, therefore, the standing in the lower working pressure chamber hydraulic fluid column is moved downward, whereby the gas present in the gas pressure chamber is compressed without a movement of the actual separating piston is required. In this respect, the working piston can be moved from its top dead center almost without damping and without much resistance in the direction of bottom dead center. Overall, the lower working pressure chamber is opened quickly towards the hydraulic pressure chamber.

According to the invention is also advantageous if the working piston is slidably disposed in a cylinder sleeve, the lower end side of the separating piston is closed. This results in not only a robust, but also a comparatively compact damper construction.

The cylinder sleeve can have passage openings for the passage of hydraulic fluid in the upper region. Consequently, hydraulic fluid can flow into the upper working pressure chamber via these passage openings when the working piston moves downwards.

The throttle opening is preferably arranged in the region of the lower end of the cylinder sleeve. The throttle opening may extend substantially radially through the wall of the cylinder sleeve. Depending on the embodiment, not only a throttle opening, but also a plurality of throttle openings may be provided. Furthermore, it is advantageous if the outer diameter of the control piston substantially corresponds to the inner diameter of the cylinder sleeve. As a result, the control piston can at least partially engage in the cylinder sleeve and, in particular, close the throttle openings provided in the cylinder sleeve.

According to the invention it can be provided that the separating piston is arranged displaceably in a cylinder housing, in which the cylinder sleeve is arranged. The diameter of the separating piston is preferably greater than the diameter of the cylinder sleeve. Consequently, hydraulic fluid can flow between the inner wall of the cylinder housing and the outer wall of the cylinder sleeve.

It is conceivable that an annular gap is provided between the cylinder sleeve and the cylinder housing, which is connected to the hydraulic pressure chamber. Cylinder sleeve and cylinder housing are preferably arranged along a common central longitudinal axis, wherein, as already mentioned, the diameter of the control piston is smaller than the diameter of the separating piston.

The cylinder housing may be closed in the upper region with a cover element. The cylinder sleeve can preferably be arranged on the cover element. Cover element and cylinder sleeve can form a common preassembled unit.

Further advantages and advantageous embodiments of the invention will become apparent from the following description, on the basis of which the Aususführungsbeispiel shown in the figures of the invention is described and explained in more detail. Show it :

1 shows a longitudinal section through an inventive damping device at top dead center;

FIG. 2 shows the damping device according to FIG. 1 shortly after leaving top dead center;

FIG. 3 shows the damping device according to FIG. 1 in a middle position;

FIG. 4 shows the damping device according to FIG. 1 at bottom dead center; and

Figure 5 shows the damping device according to Figure 1 shortly before reaching the top dead center.

The damping device shown in the figures comprises a working piston 12, the upper end may be formed, for example, as a floating plate, which is taken down by a plunger of a press. The working piston 12 is movable in a designed as a cylinder sleeve working cylinder 14 between a top dead center shown in Figure 1 and a bottom dead center shown in Figure 4. The working piston 12 limits a filled with hydraulic fluid lower working pressure chamber 16. In the working cylinder 14, throttle openings 18 are provided, via which after leaving the top dead center hydraulic fluid can flow from the lower working pressure chamber 16 to a hydraulic pressure chamber 20.

The damping device 10 further comprises a separating piston 22, in which a control piston 24 is arranged integrated. The control piston 24 is biased by means of a spring element designed as a helical spring 26 in the direction of lower working pressure chamber 16. The spring element 26 is supported at one end on the control piston 24 and at the other end on the separating piston 22. The separating piston 22 and the control piston 24 closes at the top dead center of the working piston 12, as shown in Figure 1, the working piston 12 remote from the lower end face of the lower working pressure chamber 16. The separating piston 22 together with the control piston 24 defines on the side facing away from the working piston 12 a gas pressure chamber 28th ,

Since in the idle state of the damping device 10, the working pressure in the gas pressure chamber 28 is greater than the base pressure in the hydraulic pressure chamber 20, the working piston assumes the top dead center position shown in FIG. The basic working pressure in the gas pressure chamber may be, for example, 30 bar or higher; the base pressure in the hydraulic pressure chamber at, for example, about 20 bar.

As is clear from Figure 1, the guide diameter of the control piston 24 is equal to or slightly smaller than the inner diameter of the lower

Working pressure chamber 16 so that it can engage in sections in the lower open end of the working piston 12. The control piston 24 engages in the position shown in Figure 1 as far as in the working piston 16, that he largely closes the throttle openings 18 completely. The effective effective area of the lower working pressure chamber 16 facing side of the control piston 24 is therefore the same size as the also the lower working pressure 16 facing effective surface of the working piston 12th

The separating piston 22 is displaceably mounted in a cylinder housing 30. Between the outer wall of the working cylinder 14 and the inner wall of the cylinder housing 30, an annular gap 32 is present. The central longitudinal axis of the working pressure chamber 16 corresponds to the central longitudinal axis of the cylinder housing 30. In the upper region of the working cylinder 14, passage openings 34 are provided, through which hydraulic fluid from the hydraulic pressure chamber 20 or the annular gap 32 can flow into an upper working pressure chamber 36 delimited by the working piston.

If the plunger meets the working piston 12 or a workpiece lying on the working piston 12, then this is moved downwards from its position shown in FIG. 1, that is, from the top dead center. As a result of the closed volume of the lower working pressure chamber 16 and the incompressibility of the hydraulic fluid present in the working pressure chamber 16, as shown in FIG. 2, the control piston 24 is initially moved downwards in synchronism with the working piston 12. Due to the movement of the control piston 24, the throttle openings 18 are released from the control piston 24, whereby hydraulic fluid from the lower working chamber 16 via the annular gap 32 and the passage openings 34 flow into the upper working chamber 36.

If the working piston 16 is moved further in the direction UT by the force acting from the outside on the working piston at a correspondingly high speed, the control piston 24 is moved out of the lower working space 16, as shown in FIG. The lower working space 16 is thus opened downwards, wherein from the lower working space 16 hydraulic fluid can flow over a large area. At the same time, the separating piston 22 moves downward against the force resulting from the pressure in the gas pressure chamber 28 acting on the separating piston 22 until, as shown in FIG. 4, the working piston 16 reaches its bottom dead center.

At a base working pressure of the compressed gas in the gas pressure chamber 28 of about 30 bar in the TDC position of the working piston of the Pressure in the gas pressure chamber 28 - depending on requirements and task to the press - rise to relatively high values when reaching the lower end position of the separating piston 22, which may be in the range of 200 bar or higher. It is also conceivable that the basic working pressure in the gas pressure chamber 28 can also be much higher. Depending on the stroke of the working piston and volume of the gas pressure chamber can be provided that the gas pressure in the lower end position of the separating piston 22 then increases only comparatively slightly.

Starting from its lower end position, the separating piston 22 is moved upward due to the upwardly pressing press ram and the pressure prevailing in the gas pressure chamber 28 gas pressure, which is greater than the pressure of the hydraulic fluid. The working piston 12 is also moved upward toward top dead center, since the lower working pressure chamber 16 limiting surface of the piston 12 is greater than the upper working pressure chamber 36 limiting surface. Shortly before reaching the top dead center of the working piston 12, the control piston 24 closes, as shown in Figure 5, the lower end face of the lower working pressure chamber 16. As a result, the return stroke of the working piston 12 is damped in a first stage. Upon further movement of the control piston 24 upwards this closes the throttle openings 18 depending on the distance. This results in a further damping of the return stroke of the working piston 12. The upper edge of the control piston 24 serves as a control edge, with which the throttle openings 18 are controlled.

Characterized in that the effective area of the lower pressure chamber 16 facing side of the working piston 12 is greater than the effective area, which faces in the upper working pressure chamber 36, the working piston 12 is held at top dead center. The cylinder housing 30 is closed in the upper region by a cover section 38, which may also be designed as a cover element. In the cover portion 38, a guide bore 40 is provided for the working piston 12.

The lid portion 38 may be formed integrally with the cylinder sleeve 14, for example. It is also conceivable that the lid portion 38 is formed as a genuine lid member to which the cylinder sleeve 14 is attached.

In the working piston 12, a leakage line 41 is provided, which leads from the upper working pressure chamber 36 toward the guide bore 40. A leakage bore 42 ^", which corresponds to the leakage line 41 at the top dead center of the working piston, is introduced into the cover section 38. Furthermore, the hydraulic pressure chamber 20 is connected to a hydraulic pressure source via a corresponding line 21 and pressure adjustment means (not shown) Hydraulic fluid can flow into the device 10 via the line 21 and leave the device 10 via the leakage bore 42. In this way, in particular heated hydraulic fluid can be removed from the device and fresh hydraulic fluid can be supplied to the system.

The gas pressure chamber 28 may be connected via a corresponding line 29 with a gas pressure control valve, not shown, via which the working pressure in the gas pressure chamber 28 is adjustable.

The illustrated in the figure embodiment of the invention has the following particular advantages: To adjust the bias of the damping device 10, only the gas pressure in the gas pressure chamber 28 is changed. A change in the pressure in the hydraulic pressure chamber 20 is not required. To the another provides the working piston 12 when hitting the plunger of the press a comparatively low resistance, so that arise for the press, or the workpiece to be produced, overall advantageous conditions. Furthermore, it is advantageous that a suitable damping of the return stroke movement of the working piston is achieved due to the path-dependent control of the working pressure chamber 16.

Claims

claims

1. Damping device (10) for damping the return stroke movement of a plunger of a press from a top dead center OT in a bottom dead center UT convertible working piston (12), wherein the working piston (12) is movably arranged in a working cylinder (14) and one with Hydraulic fluid fillable lower working pressure chamber (16) limited, with a separating piston

(22), with which the lower side of the lower working pressure chamber with respect to a hydraulic pressure chamber (20) is closable and on the working piston (12) facing away from the lower side of a gas pressure chamber (28), wherein when moving the working piston (12) from the TDC in Direction UT hydraulic fluid from the lower working pressure chamber (16) is urged into the hydraulic pressure chamber (20) and the separating piston (22) moves in the direction of the lower end position, and wherein the separating piston (22) is moved after reaching its lower limit position upwards while the lower working pressure chamber (16) path-dependent closes.

2. damping device (10) according to claim 1, characterized in that Gasdruckeinstellmittel are provided for adjusting the gas pressure and that Hydraulikfüßigkeitseinstellmittel are provided for adjusting the Hydraulikfüßigkeitsdrucks, wherein the gas pressure is independent of the hydraulic fluid pressure adjustable.

3. damping device (10) according to claim 1 or 2, characterized in that at least one of the lower working pressure chamber (16) to the hydraulic pressure chamber (20) leading to the throttle opening (18) is provided and that the separating piston (22) in an intermediate position only the lower working pressure chamber (16) and in its upper End position also closes the at least one throttle opening (18).

4. damping device (10) according to claim 1, 2 or 3, characterized in that the working piston (12) can be filled with a hydraulic fluid upper working pressure space (36), wherein the upper working pressure chamber (36) via passage openings (34) with the hydraulic pressure chamber ( 20) is connected.

5. damping device (10) according to one of claims 1 to 4, characterized in that the hydraulic pressure chamber (20) and the gas pressure chamber (28) are formed as each closed pressure chambers.

6. damping device (10) according to any one of the preceding claims, characterized in that the separating piston

(22) a by means of a spring element (26) in the direction of lower working pressure chamber (16) biased control piston

(24), whose outer diameter substantially corresponds to the inner diameter of the working cylinder (14) and engages to shoot the lower working pressure chamber (16) in the working cylinder (14).

7. damping device (10) according to claim 6, characterized in that the at least one throttle opening (18) in the region of the lower end of the working cylinder (14) is provided and that the control piston (12) in the upper end position of the separating piston, the throttle opening (18 ) closes.

8. damping device (10) according to claim 6 or 7, characterized in that when moving the working piston (12) from top dead center TDC in the direction of bottom dead center UT due to the lower working pressure chamber (16) increasing pressure of the control piston (24) against the biasing force of Spring element (26) and the gas pressure in the gas pressure chamber moves down and thereby first the throttle opening (18) is opened then the control piston (24) together with separating piston (22) moves down and the lower working pressure chamber (16) is opened towards the hydraulic pressure chamber.

9. damping device (10) according to at least one of the preceding claims, characterized in that the working cylinder (14) is designed as a cylinder sleeve whose lower end face of the separating piston (22) is closable.

10. damping device (10) according to claim 9, characterized in that the working cylinder (14) in the upper region passage openings (34) for the passage of hydraulic fluid.

11. damping device (10) according to claim 9 or 10, characterized in that the throttle opening (18) is arranged in the region of the lower end of the cylinder sleeve.

12. damping device (10) according to at least one of the preceding claims, characterized in that the separating piston (22) in a cylinder housing (30) is arranged displaceably, in which the working cylinder

(14) is arranged.

13. damping device (10) according to claim 12, characterized in that between the cylinder sleeve and the cylinder housing (30) an annular gap (32) is provided which is connected to the hydraulic pressure chamber (20).