EP1203161B1 - Security valve for a press - Google Patents

Description

The invention relates generally to hydraulic safety valves and in particular a safety valve unit according to the preamble of claim 1.

Document DE-A-3008935 discloses a safety valve unit according to the preamble of claim 1.

Hydraulic safety valves of the affected here Type will be e.g. for controlling the brake and / or clutch used a mechanical press. That's how it is DE 38 17 123 A1 already a hydraulic valve became known for the aforementioned application, the by two electromagnetically operated pilot valves is controlled. The valve also has two opposite directions mutually movable valve body with control piston on. By means of the control piston, the connections between a pump connection, two working connections and two tank connections controlled. at If there is a malfunction, the valve bodies go into a hydraulically locked end position. Especially is one of the two pilot valves as a proportional pressure differential valve trained, with his assigned Control spool provided with fine control notches are, so that the valve proportionally controlled and thus the pressure build-up, the speed and the direction of movement a consumer downstream of the valve are controllable.

In DE 196 20 468 A1 is also a safety valve described in which in a housing two parallel arranged working piston are arranged, of which each with a valve plate is firmly connected. Both Working pistons become electromagnetic by means of pilot valves driven. In the housing an inlet is formed, connected to a compressed air source is. The inlet leads to the valve plates, which means Cross channels are interconnected crosswise. Via a consumer connection, a consumer, e.g. a piston drive of a mechanical press, in the switching position of the safety valve pressurized will be in a zero position the Consumer vented via a vent port is. One channel branches off each of the cross channels each of the pilot valves. Furthermore, runs from each Pilot valve a channel to the associated working piston. In addition, each pilot valve with a solenoid provided, and each solenoid is over a Power supply line connected to a power source, which is part of a machine control.

To increase the productivity of mechanical consumers is to increase mechanical pressing or the like it required the speed of the piston drive to increase.

Furthermore, it is increasingly being used, whole To unite press lines in single large press. However, these presses require correspondingly large clutch / brake units, around the high hydraulic Cope with switching volumes, these clutch / brake units either in unit or separately can be arranged.

The above, known in the art Safety valves are exclusively in piston slide valve technology executed, whereby their maximum Flow rate is limited. In addition, these valves require due to the required during a switching operation Piston strokes long switching times when coupling and Braking the press.

Summary of the invention

The invention is therefore based on the object, a Hydraulic valve arrangement of the type mentioned specify the shortest possible switching times of a mechanical consumer, in particular as short as possible Clutch and brake operations on a mechanical press, provides while still a possible ensures high operational safety.

This task is characterized by the characteristics of the independent Claim 1 solved. Advantageous embodiments of Invention are the subject of the dependent claims.

The invention provides for a for the operation of a mechanical Consumer's suitable safety valve unit of the type mentioned, which means at least a pressure connection with a hydraulic Pressure source, by means of at least one working port with the hydraulic consumer and by means of at least a tank connection with a hydraulic fluid connected tank, and which at least having two working valves by means of at least an electrically controllable control valve are operable, the at least two working valves are designed as seat valves, and wherein the at least two work valves operated in opposite directions be, with the first working valve in the open state the pressure connection at least with the working connection connects and that the at least second working valve in the open state with the work connection the tank connection connects, in particular before, that the at least second working valve by means of a spring force is normally open.

The seat valve construction used in the valves mentioned allows in particular high flow rates and at the same time very short switching times of these valves, because of this design already low piston movements almost no time delay to large valve port cross sections to lead.

Brief description of the drawings

Embodiments of the invention will be described below described on the basis of drawings that make up more Features and advantages of the invention. In The drawings are identical or functional same features with matching reference numerals Mistake.

Fig. 1a

eine hydraulische Ventilanordnung mit einer Sicherheitsventileinheit und einer Dämpfungsventileinheit gemäß einer ersten Variante;

Fig. 1b

eine der Fig. 1a entsprechende Ventilanordnung mit einer gegenüber der Fig. 1 unterschiedlichen Variante der Dämpfungsventileinheit; und

Fig. 2

ein Funktionsablaufdiagramm zur Illustration der Arbeitsweise der in Fig. 1a und 1b gezeigten Ventilanordnungen.

In detail show:

Fig. 1a

a hydraulic valve assembly having a safety valve unit and a damping valve unit according to a first variant;

Fig. 1b

a valve arrangement corresponding to FIG. 1a with a variant of the damping valve unit which is different from that of FIG. 1; and

Fig. 2

a functional flow chart for illustrating the operation of the valve arrangements shown in Fig. 1a and 1b.

Detailed description of the embodiment

Fig. 1 shows a hydraulic valve assembly consisting from two assemblies, namely a safety valve unit 10 and a damping valve unit 20. The two units 10, 20 are connected via a pressure connection 30 with a hydraulic pump 40, via a tank connection 50 with a hydraulic fluid tank 60 and over a working connection 70 with a mechanical consumer, one for operation in the present example a (not shown here) mechanical Press provided clutch and / or brake piston 80, connected hydraulically or pressure-conducting. On the hydraulic fluid it does not matter here; it may therefore be either a gas or a liquid.

The safety valve unit 10 has a first in Seat valve design trained 2/2-way valve 90, in which a reaching into a valve chamber 100 Piston 105 with one on the inside of the valve housing trained annular surface forms a valve seat 110. This valve seat 110 connects or disconnects one from the pressure port 30 outgoing pressure line 120th with an outgoing from the work port 70 working line 130. The two lines 120, 130 are in interrupted in the present operating state (closed).

An active movement of the piston 105 to operate the Valve 90 is also hydraulic, via a (Valve) control chamber 115. The directional control valve 90 also has a designed as an inductive switch proximity switch (S3) 95, by means of which the operating state the directional control valve 90 can be sensed.

Furthermore, two are also trained in poppet design 2/2-way valves 140, 150 are provided, in which on an inner annular surface 160, 170 about to concern upcoming piston 155, 165 form a valve seat, and in the currentless operating state shown by means of Spring preloads 180, 190 are open. Therefore, find the directional valves 140, 150 in particular in the case of Energy failure in the safe "open" position, in which the working line 130 is relieved. Also at These valves 140, 150, the piston 155, 165 hydraulically moved via control chambers 162, 175 (active). In addition, the directional valves 140, 150 each have one Proximity switch 145, 155 with the above Functionality on.

Because of all designed in poppet design 2/2-way valves along with in the area of each Valve seat arranged (not shown here) pressure sensors offers, in combination with the fast valve switching times, a high level of operational safety.

Since the working line 130, parallel to the connection with the first directional control valve 90, also with the valve chambers 200, 210 of the two-way valves 140, 150 connected is the working line 130 in the present situation via a hydraulic fluid tank 60 leading Tank line 220 relieved hydraulically.

To increase the reliability of the entire valve assembly are the two 2/2-way valves 140, 150th functionally identical. Their parallel connection In addition, this means additional operational safety increasing redundancy, ensuring safe braking the clutch and / or brake piston 80 always guaranteed is.

As already said, the directional control valves 90, 140, 150 by each via the control chambers 115, 162, 175 driven Movements of the pistons 105, 155, 165 connected. The control chambers 115, 162, 175 are to this Purpose to a dashed line in the drawing hydraulic control line system 225 connected.

The safety valve unit 10 also has two as 4/2-way valves formed pilot valves 230, 240th on, connected by means of electromagnets 235, 245 become. The pilot valves 230, 240 connect either (as shown here) the control chamber 115 of the first Directional valve 90 with the pressure line 120, and thus also the pump 40, and the control chambers 162, 175 of the directional control valves 140, 150 with the tank line 220, and so also the tank 60. In a (not shown here) Cross position, however, the control chamber 115 with the tank line 220 and the control chambers 162, 175 with the pressure line 227 connected.

Since all 2/2-way valves 90, 140, 150 of the same Pilot valves 230, 240 are actuated, works the entire arrangement in the manner of a forced circuit, whereby all operating states are unique are fixed.

The damping valve unit 20 has a proportional pressure relief valve 250 on, by means of a spring preload normally closed and that over one Control current is controlled or opened. Thereby is guaranteed that even with an electric Power failure the press via the clutch or brake piston 80 can be braked soft.

A proportional pressure reducing valve 260 allows a Pressure modulation during soft coupling and different Pressure levels when engaging the press by means of Clutch piston 80.

A pressure limiting valve 270 serves for maximum pressure protection the driven by the clutch piston 80 Clutch. The pressure limiting valve 270 prevents too high actuating pressure in the coupling, for example, by a faulty control of the proportional pressure reducing valve 260 could arise.

Finally, the damping valve unit also has a Spring accumulator 290, which provides a permanent back pressure in the tank line, in particular during a soft braking phase, guaranteed and thus a more controlled Braking the press allows.

In the following, the functional sequence of the shown Valve arrangement described in more detail, being also on Fig. 2 is to be referenced.

In the basic position shown in Fig. 1, the electromagnets 235, 245 of the pilot valves 230 and 240 de-energized. As a result, the directional control valves 140 and 150 switch by means of the respective spring preload 180, 190 in the open position, wherein the inductive switch 145 and 155 be damped. The directional control valve 90 is in the Basic position closed and its inductive switch 95 undamped.

The transmitted via the pressure line 120 pump pressure acts accordingly on the annular surface of the valve piston 105th of the directional valve 90. At the same time, the pilot valves 230, 240, the directional control valve 90 due to the area difference the two sides of the piston in the closed Held position.

Between the pump connection 30 and the working connection 70 and the tank connection 50 is not connected and therefore, the working port 70 is above the tank line 220 and the tank port 50 relieved.

Before from the basic position into a switching position can be transferred, the proximity switch 95th the closed, i. acknowledge undamped position. Accordingly, the proximity switches 145 and 155 must S2 the present opened, i. damped position Acknowledge.

In the switching position, the electromagnets 235, 245th the two pilot valves 230, 240 energized. Thereby becomes the directional control valve 90 leading part of the control line 225 relieved to the tank 60 down. In addition will be the directional valves 140 and 150 closed. In the Switching position is the pump connection 30 with the working connection 70 connected. The connection between the Work port 70 and the tank port 50 is, however, blocked.

It is now a malfunction of one of the pilot valves 230, 240 assumed, wherein the electromagnet 245 of Pilot valve 240 energized and the solenoid 235th the pilot valve 230 is de-energized. Therefore only will the directional control valve 150 is closed, whereas the directional control valve 140 remains open. Consequently, the connection remains between the working port 70 and the tank port 50 open. Thus, at the work connection 70 do not build up pressure, which is a high safety factor represents. The mentioned malfunction (switching) is also due to the unequal signaling of the proximity switch 145 and 155 in the (not shown here) Control recognized as such.

To detect such or similar malfunctions During a press stroke, the proximity switches are switched 145, 155 and 95 cyclically checked.

With the damping valve unit becomes a soft engagement and braking achieved.

When soft coupling is in addition to the pilot valves 230, 240 and the solenoid 265 of the proportional pressure reducing valve 260 excited, the latter so with Power is controlled that the secondary pressure the Pump pressure corresponds. This ensures that the stroke volume quickly to the clutch-brake combination flows. This means a quick response of the Clutch.

When the clutch closes, the current at the proportional pressure reducing valve becomes 260 lowered again, causing the secondary pressure up to the desired soft-coupling pressure drops. After the acceleration process is the Current at the proportional pressure reducing valve 260 then again increased, so the pressure determined for the clutch up rises to a nominal pressure.

When soft braking, however, the electromagnets 235, 245 of the pilot valves 230, 240 de-energized and the Solenoid 255 of the proportional pressure relief valve 250 excited, the latter so is energized that it opens completely.

The hydraulic generated by the clutch / brake combination Switching volume now flows through the proportional pressure relief valve 250 in the tank 60 from. Short before the brake closes, the current at the proportional pressure relief valve 250 lowered again, so that in leading to the work terminal 70 line build up a pressure. This soft brake pressure acts in the type of backpressure and causes the Soft braked press. The height of the soft brake pressure is determined by the modulation of the proportional pressure relief valve 250 determined.

The damping valve unit therefore allows optimization the start and stop process of the press and thus ensures high security for the entire Production facility. In addition, it can be lower the operating noise level of the press and the reduce mechanical load on the press drive, resulting in longer service life of the production facility leads.

FIG. 1b shows a valve arrangement corresponding to FIG. 1a different with respect to FIG. 1a formed damping valve unit 20, however with a matching safety valve unit 10. Regarding the features and function (s) of the safety valve unit is therefore completely on refer to the comments on Fig. 1a.

In the embodiment of FIG. 1b is in addition a directional valve 310 formed way valve 300 provided to the pressure relief valve 250th is connected in parallel. The directional control valve 300 is over a pilot valve 330 is driven. Due to the seat valve design be, similar to the way valves 140 and 150, high flow rates and shorter switching times when braking, especially in the danger area of Press, possible. The directional control valve 300 is in the de-energized Condition is opened by a spring force 320 and is located in the basic position, especially in the Fall of a power failure, in the open position. The open position of the directional valve 300 allows in addition, a very fast switching and very effective EMERGENCY STOP or fast braking of the press (via the piston 80), as one in the working line 130th about existing hydraulic pressure over the lines 223, the tank line 220, and in particular on the Routing 222 are reduced almost instantaneously can.

Another advantage of the seat valve construction of the directional control valve 300 is that the damping valve unit 20 directly over the valve seat 310 of the directional control valve 300 can be monitored, resulting in a particularly high Ensured safety with respect to the damping behavior is.

• Spannungsverlauf 500 an den Elektromagneten 235, 245 der Vorsteuerventile 230, 240;
• Stromverlauf 510 am Elektromagneten 265 des Proportional-Druckminderventils 260;
• Stromverlauf 520 am Elektromagneten 255 des Proportional-Druckbegrenzungsventils 250;
• Druckverlauf 530 in der Kupplung/Bremsenkombination der Presse; sowie
• Drehzahlverlauf 540 in der Antriebswelle der Presse.

FIG. 2 illustrates the functional sequence of the valve arrangements shown in FIGS. 1a and 1b on the basis of the time sequence of the following variables, which are called from top to bottom in the sequence according to FIG. 2:

• Voltage curve 500 to the electromagnet 235, 245 of the pilot valves 230, 240;
• Current path 510 at the electromagnet 265 of the proportional pressure reducing valve 260;
• Current path 520 at the electromagnet 255 of the proportional pressure relief valve 250;
• Pressure curve 530 in the clutch / brake combination of the press; such as
• Speed curve 540 in the drive shaft of the press.

By driving the pilot valves 230, 240 go They cross over and open the directional control valve 90, since the control chamber 115 now via the tank line 220 is relieved. At the same time close the two-way valves 140 and 150, since the control chambers 162, 175 are subjected to the pump pressure and thereby moving the pistons 155, 165 to the seating position become.

After a certain lead time (hydraulic settling time) thus increases the pressure on consumers, here the clutch / brake combination. After getting there a pressure has built up, the speed increases the drive shaft of the press up to a rated speed steadily. By actuating the proportional pressure reducing valve 260 is the pressure increase allerings damped, which slows down the overall shown Increasing course of the speed results.

After the directional valves 90, 140, 150 by switching again the pilot valves 230, 240 back into the Change over to basic position, is the proportional pressure relief valve for a short time 250 controlled, whereby the at the consumer 80 present pressure increases over the Tank line 220 can be reduced. After a time delay Then the speed falls back on the original value.

The already mentioned switching delay when opening the Directional valve 90 opposite the directional control valves 140, 150 prevented the formation of a hydraulic short circuit between point A of the directional valve 90 and the points B of the directional control valves 140, 150. In addition, this is a Starting the press even without a soft coupling allows. Furthermore, the temporal overlap can be and thus adjust the soft-coupling pressure externally.

It is understood that the valve arrangement according to the invention not only advantageous for mechanical presses can be used, but wherever large Masses by means of a hydraulically operated clutch and / or brake are moved.

Claims (6)

1. Safety valve unit for the operation of a hydraulic consumer (80), which is connected by means of at least one pressure connection (30) to a hydraulic pressure source (40), by means of at least one working connection (70) to the hydraulic consumer (80), and by means of at least one tank connection (50) to a tank (60) containing hydraulic fluid, and which has at least two working valves (90, 140), which can be actuated by at least one electrically operated control valve (230), the minimum of two working valves (90, 140) being designed as seat valves (110, 170) and the minimum of two working valves (90, 140) being operated in opposite directions, where the first working valve (90), when in the open state, connects the pressure connection (30) at least to the working connection (70), and in that the minimum of one second working valve (140), when in the open state, connects the working connection (70) to the tank connection (50), characterized in that the minimum of one second working valve (140) remains open under the force of a spring (180) when de-energized.
2. Safety valve unit according to Claim 1, characterized in that the minimum of two working valves (90, 140) are designed as 2/2-directional control valves and the minimum of one control valve (230) is designed as a 4/2-directional control valve, where the minimum of one control valve (230) connects the piston chambers of the minimum of two working valves (90, 140) in opposite directions to the pressure connection (30) and to the tank connection (50).
3. Safety valve unit according to Claim 1 or 2, characterized in that the minimum of two working valves (90, 140) can be actuated by the same control valve (230), of which there is at least one.
4. Safety valve unit according to one of the preceding claims, characterized in that a minimum of two second working valves (140) are provided in the form of two parallel-connected 2/2-directional control valves.
5. Safety valve unit according to one of the preceding claims, characterized in that the first working valve (90) is actuated with a time delay with respect to the minimum of one second working valve (140).
6. Safety valve unit according to one of the preceding claims, characterized in that each of the minimum of two working valves (90, 140) has an inductive switching position sensor (95, 145).

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