DE2649793C2 - Safety control for a hydraulically operated press - Google Patents

Description

ä) the main control piston (13) of the second switching valve (12) also has three switching positions ^: L, 2, Mt ₂ , Ä12

b) if one of the main pistons gets stuck (13,14) the downward movement of the piston (8) of the working cylinder (3) is blocked

c) at least one (11) of the switching valves (11, 12) via two separate pilot valves (15, 16) 25 The main control piston (13) of the first switching valve is pilot-controlled and by hydraulic pressure (11) can be brought at least into its middle position and in the middle position Mi and / or M12 at least one of the switching valves (11 and / or 12) a downward movement of the work; 'ughalters (1) is blocked

d) in the middle position M _{u of} the main control piston (13) of the one switching valve (11) all paths (Hi to H ₄ ) of the Sdialt valve (11) are closed,

e) also in the middle position Mn of the main control piston (14) of the second switching valve

(12) two paths (12 | and I23) are closed and the other two paths (12 ₂ and 1%) are connected to one another and, as a result, the space (6) of the rapid traverse cylinder (2) is connected to the return (9),

f) further a first path (lli) of the first switching valve (H) with the pressure oil source (21) and a second path (11 2) with a third path (12j) of the second switching valve (12), a third path (Hj) with the ring space (5) and a fourth path (II4) are connected to the space (6) of the rapid traverse cylinder (2),

g) in one position (Lu) of the main control piston

(13) of the first switching valve (12) the first path '"(Hi) with the fourth path (II4) and also the second way (II2) with the third way (1 Ij) and

in the other position (R _t \) of the main control piston (13) the first path (Hi) and the second path (Hj) are connected to the third path (1 Ij) and the fourth path (114) is closed,
h) at the second switching valve (12) a first path (I2i) with the space (7) of the working cylinder (3), a second path (12 ₂ ) with the return (9), a third path (123) with the second path (II2) of the first switching valve (11) and via a working 'pressure relief valve (22) with the return' (91 a fourth path (H ₄ ) with the space (6) of the *>*> . '. Eilgarig cylinder (2) and the fourth path (II4) of the first switching valve (11) is connected,, _'....; , i | ,. in an end position (Ln) des.Hauptsteuerkol-

bens (14) of the second switching valve (12) the first 'Wegto mildem vierfeh- # eg''tou ^' aejr

k)

Wegto mildem vierfeh # egto, u ^ aejr second way (lij 'is connected to the old ^ Wre ΜΆ ,' \ -vr.-τ, ^ * M,%

in the other 'Endteilüng'Ma) of the l' ^J fiaufi \ - control piston (14) i of the second 'ScfiättvenHs (12) the first way (12,) üriUcjef Viefie ^ W ^ (ii) closed and the second way'(# 2) is connected to the third path (I23) and '.'" In the middle position (M _t $ of the main control piston (14) of the second switching valve.if, ti) the first path (12i) and the third path (12 ₃ ) closed and the second path (I22) is connected to the fourth path (124)

2. Safety controller according to claim 1, characterized characterized in that both pilot valves (15, 16) controlling the first control valve (11) are 4/2-way valves are.

3. Control according to claim 1, characterized in that the middle position (Mu) of the first switching valve (12) takes place in each case by a displaceable end-face ring (26,26 '), the ring area of which is about twice as large as the effective piston area (27, 27 ') for adjusting the pressure of the main control piston (13).

4. Control according to claim 1, characterized in that the main control piston (13, 14) at least one of the switching valves (11, 12) is spring-centered in the middle position fJVfa), e.g. B. by two counteracting springs (17,18).

5. Control according to claim 1, characterized in that that between the third way (II3) and the annular space (5) of the rapid traverse cylinder (2) Holding valve (23) is provided

6. Control according to claim 5, characterized in that the holding valve (23) has a bypass channel with a check valve (24)

7. Control according to claim 1, characterized in that the pressure oil, je! Le (21) via a controllable holding valve (25) can be connected to the return line (9).

8. Control according to claim 3, characterized in that in the neutral position of the two pilot valves (15, 16) the main control piston (13) of the first switching valve (U) is held in the central position (Mu) and in the working position (Lu) or (Ru) the associated pilot valve (15 or 16) relieves the pressure on one end face of the main control piston (13) of the switching valve (11).

9. Control according to claim 1 and 4, characterized in that the second switching valve (12) can be controlled via a 4/3 pilot valve (19) and in the middle position (Mm) of the pilot valve (19) both end faces of the main control piston (14) pressure-relieved and in the two other working positions one face is relieved of pressure and the opposite face of the main control piston (14) is pressurized.

The invention relates to a safety control for a hydraulically operated press, in which at least one single-stroke cylinder and one working cylinder can be controlled via at least two switching valves. are: and _; to,

's in the ftjngjaum unterialb'd ^ a piston

er ^ ljjjdef ^ d, ^ iriaesteps, a. Eauni pber the CoIben ^J can be shut off selectively with a Bruck oil well or a reflux connectable or davpn wherein dej- ^L 'Haiipfeteüerkölben of a switching valve three 5 switching positions and, Haüpfsteuerkolben of zweifen Sbhältv ^ entjls at least two switch positions having ^'.

In one known from DE-OS 16 27,864 Safety control is that three switch positions having the main vehicle switched via two magnets and; held in its central position by springs. There, reach a sufficient press speed to be able to control the cross-sections must be kept relatively large with appropriate Main control piston diameter, the springs and magnets must also be dimensioned accordingly large will. Due to the accumulation of dirt, there is now a risk of the main control piston becoming sluggish, so that a 100% security against getting stuck in the main control valve is not given But then there is a risk of getting stuck in The next control process unintentionally creates a dangerous work situation by lowering the tool holder can occur. The same applies to that only further switching valve having two switching positions. Similar dangerous situations can also occur with unnoticed breakage of a spring occur, in which the main control piston is no longer in its rest position can be traced back.

From US-PS 34 52 399 it is known pressure medium-operated Pilot valves by solenoid valves, so-called pilot valves, if the occurring Medium pressures in direct controls lead to very large and complex actuating magnets would.

The object of the present invention is to provide a safety controller of the type mentioned at the beginning improve that, despite any malfunctions that may occur in the individual control elements, there are no dangerous Downward movement of the working cylinder is possible, so that with such a safety control equipped presses can be operated by hand without risk.

This object is achieved by the characterizing features of claim 1.

In particular, by using two separate pilot valves for controlling the first switching valve, the switching reliability is significantly increased. First, by using the pilot valves, the 5 «main control piston itself is adjusted by hydraulic forces. These forces can be much higher than achievable by magnets forces the piston can be overcome without interference so that the resistance of small dirt during the movement of the Hauptsteue ^r. On the other hand, if a pilot valve gets stuck in a further switching sequence with activation of the other pilot valve by the main control piston, switching through is not possible, but at most reaching the middle position, in which the downward movement of the tool holder is blocked, so that a dangerous situation does not occur at all in the event of a malfunction can. The same also applies to the second control valve. In its central position, the downward movement of the tool holder is blocked and the second control valve must be brought over the central position in order to move from a display position for a working movement to a different switching position for another working movement.

The safety control is sure to "go into fault" even in the event of a fault. ^ S Pilotventiis can this ensures that at least one of the control valves can be controlled via two separate pilot valves is, with expediently both, .Pilot valves 4/2-way valves are ■

The paths of the switching valves can advantageously be switched in such a way that one is already in the middle position the switching valve, the downward movement of the piston of the working cylinder is blocked. This can be advantageous the main control piston at least one of the switching valves by hydraulic pressure in its middle position be bringable. It is advisable to cry through each time displaceable end-face ring, the ring area of which is about twice as large as the effective piston area for adjusting the pressure of the main control piston. This means that even if a higher Friction still reached a middle position due to the larger force occurring, while a Working position due to friction. / cht absolutely more has to be achieved. By dk. sure Achievable middle position is - as mentioned above - the downward movement of the piston of the Working cylinder locked.

A substantial increase in safety can still be achieved in that the pressure oil source has a The controllable holding valve can be connected to the return. A pressure above the necessary holding pressure for the Preventing the lowering of the piston read the working cylinder taking into account the weight of the tool can only be set up when the holding valve is energized, so that, for safety's sake, it is already in all stop positions There is no longer any working pressure in the entire printing system wrong control piston alignment no more harmful effect can be caused.

The invention is explained in more detail below with the aid of an exemplary embodiment shown in the drawings explained. It shows

F i g. 1 shows a circuit diagram of an embodiment of a safety control with working cylinder and Rapid traverse cylinder,

2 shows a schematic representation of one in the F i g. 1 shown switching valve and

F i g. 3 is a schematic representation of another in FIG. 1 switching valve also included.

The in F i g. 1 schematically illustrated tool holder 1 of a hydraulic press can via a Rapid traverse cylinder 2 and a working cylinder 3 are raised and lowered in a known manner. To the The tool holder 1 is raised in rapid traverse in a position below the piston 4 of the rapid traverse cylinder 2 angeird. esen annulus 5 supplied pressure oil. The space 6 of the rapid traverse cylinder opposite the piston 4 2 and a Rau.η 7 above the piston 8 of the working cylinder 3 are then with a return 9 in Connection to allow the displaced pressure oil to flow out. A lowering of the tool holder 1 in rapid traverse can take place if pressure oil is supplied in space 6 of the rapid traverse cylinder 2. Through the piston 8 moving downward emerges in space 7 of working cylinder 3 through a negative pressure via a suction valve OK oil with the corresponding Speed can be sucked in. During the subsequent work stroke, room 7 Pressure oil is supplied and so the desired pressing force corresponding to the large area of the piston 8

of tool holder 1 reached.

To safely control the movement of the tool holder 1, two separately arranged switching valves Π and 12 are provided. The main control piston 13 of the one switching valve 11 can assume three switching positions and the valve 11 can be connected via four paths Hi to II4. The other switching valve 12 is also designed accordingly. Its main control piston can also be brought into three positions and it is via the paths 12 | connected to 12 ₄ . Both switching valves 11 and 12 are 4/3 way valves. In the case of the switching valve II, the main control piston 13 is adjusted purely hydraulically via two separate pilot valves 15 and 16. Both pilot valves 15 and 16 are designed as 4/2 way pilot valves.

In contrast, the main control piston 14 of the other switching valve 12 can be centered in its central position by means of two springs 17, 18 arranged at the end, as shown in V 1 g. J can be seen and is described in more detail below. The adjustment of the main control piston 14 takes place in turn via a pilot valve 19, which is designed as a 4/3 way pilot valve.

As can be seen from FIG. 1, the path Hi of the switching valve 11 is connected to a pressurized oil source 21 with the interposition of a check valve 20. The path H ₂ is connected to the path 12 _{3 of} the other switching valve 12. This connecting line is also connected to the return 9 via a working pressure limiting valve 22 in order to prevent an undesirable, dangerous pressure increase. If, for example, the annular space 5 is not connected to the return line 9. When the space 7 is pressurized, the different effective piston areas between the rapid traverse cylinder 2 and the working cylinder 3 result in an impermissibly high pressure in the annular space 5. This pressure increase is reduced by the working pressure limit! 22 limited.

The path lh of the switching valve 11 is via a Holding valve 23 and a check valve 24 connected in parallel to the annular space 5 in connection. That Holding valve 23 is adjustable so that an outflow of the pressure oil from the annular space 5 only after reaching a certain pressure can take place. The pressure is adjusted so that the entire weight of the not illustrated tool, the tool holder 1, the piston 4 and the piston 8 with the associated Piston rods and the pressure oil overlying it is safely absorbed without the tool holder 1 can fall, so that even in the event of a complete failure of the pressure oil supply, there is no independent Going down of the tool holder 1 is possible

Finally, the path XU of the switching valve 11 is directly connected to the space 6 above the piston 4 of the rapid traverse cylinder 2 and also to the path 124 of the other switching valve 12.

As shown in FIG. 1 can also be seen, the path 12i of the other switching valve 12 is still connected to the space 7 above the piston 8 of the working cylinder 3, while the path 12 _{2 of} the other switching valve 12 is directly connected to the return 9

To increase safety, there is also the pressurized oil source 21 connected to the return line 9 via a controllable holding valve 25. This controllable holding valve 25 serves on the one hand to limit the maximum pressure of the pressure oil source ίί and on the other hand to increase the Operational safety, because the holding valve is in the rest position 25 in line-up so that the supply line von der 't) rucköiquelle "21 is without pressure and thus the

Device is blocked.

In the Lu position of the main control piston 13, the path 111 is connected to the path lh and the path H _{2 is} connected to the path lh. In the middle position Mu of the main control piston 13, all routes Hi to II4 are closed and in the position Ru of the main control piston 13, the routes III to 113 are connected to one another, while the route II4 is closed, as can be seen from the schematic illustration in FIG .

Correspondingly, in the position Ln of the main control piston 14 of the other switching valve 12, the path 12 | with path 12 * and path 12 ₂ in connection with path 12 _3. In the middle position Mn of the main control piston 14, the paths 12 | and 12 ₃ closed, while the paths 12 ₂ and 12 ″ are connected to one another. Finally, in the position Rn of the main control piston 14 of the other switching valve 12, the paths 12; and \ 7-. closed and the paths 12 ₂ and 12 ₃ in connection with one another.

The following overview shows the respective position of the switching valves 11, 12 and the holding valve 25 for the various machine functions.

function Valve positions Switching Hold r the Switching valve 12 valve 25 ι Mascb nc valve 11 Mn Rest position Standstill M _n Marg Working position Express from Lu M _n Rest position stop M ₁₁ Ln Working position Load off L _n Mn Working position Hurry up Ru

At a standstill, the tool holder 1 is held by the blocking of the path H ₃ by the switching valve 11. But even if the switching valve 11 gets stuck in a position other than the middle position, the tool holder cannot sink, since there is no pressure due to the holding valve 25, which is open in its rest position, and the tool holder 1 sinks due to its own weight due to the Holding valve 23 and also the check valve 20 is prevented. Any position of the other switching valve 12 cannot cause the pressurized oil to flow out of the annular space 5 either. A return flow of the oil from the R ^: jgraum 5 is additionally prevented in the switching position Ln by the working pressure limiting valve 22
With the function "express from" the main control piston 13 in the position Ln and the main control piston 14 of the other switching valve 12 in the position R, _n, reaches the main spool 13 is not the position L \\ nothing happens, because then the zero position of the switching valve 11 every movement is blocked

ω main control piston 14 does not change its position R \ r, but remains stuck, so the line touching to space 6 remains connected to return 9 via paths 124 and 122, while the connection line to annulus 5 is blocked by the main control slide ^

ή is, so that the pistons 4 and 8 stop.-i ^ Qjnmt the holding valve 25 is not in its working position, there is no pressure and again no adjustment can take place. Only when the main control piston · 13πι its

Position L _u arrives and the holding valve 25 is in its working position and, in addition, the other switching valve 12 is in its position Ru , the pistons 4 and 8 with the tool holder 1 can move at rapid traverse. This provides multiple security. If a switching function of one of the switching valves II, 12 and of the holding valve 25 fails, the device goes to “StöruTg” and the damage thus noticed can be repaired without any risk to the operating personnel.

If, for example, the main control piston 13 gets stuck from the transition from the fast-moving function to the stop, the space 6 above the piston 4 of the fast-moving cylinder 2 is created by the main control piston 14 of the switching valve 12 via the paths 12 ″ and 12 ₂ with the return 9 connected and at the same time the line "fast open" interrupted, so that a standstill occurs. If the main control piston 14 does not drop, a function of the input cylinder 2 of the working cylinder 3 is also prevented, since the main control piston 13 of the switching valve 11, which is in the Mn position, prevents any supply of pressurized oil. If, as a last resort, the holding valve 25 does not fall into its rest position, the Mn position of the main control piston 13 likewise interrupts any supply of pressurized oil to the cylinders 2 and 3 again. Only the pressurized oil source 21 does not get a "pressureless" circulation. A falling switching valve 11 or 12 is thus sufficient for safely stopping cylinders 2 and 7 from rapid traverse. It is extremely unlikely that both switching valves 11 or 12 fail at the same time during a switching process; such a case does not have to be taken into account even with an extremely safe safety control.

To initiate the working stroke of the working cylinder 3 ü, the switching valve 11 is in the position Ln, the switching _{valve 12 is in the position Li 2} and the holding valve 25 is in its working position. If one of the valves mentioned does not reach this position, the movement of the pistons 4 and 8 is blocked in practically the same way as was described for the "rapid down movement".

In the "fast-open movement", the main control piston 13 of the switching valve 11 is in the Ru position, the main control piston 14 of the other switching valve 12 is in its position Mi ₂ and the holding valve 25 is in its ->> working position. If the main control piston 13 of the switching valve 11 does not move into the An position, but remains in its central position Mn, the blocking of the paths II3 and 1112 prevents the piston from moving if the main control piston 14 of the other switching valve were in the Li _{2 position} , the path H of the switching valve 11 is connected ₂ via the paths 12 ₃ and 12 ₂ to the return line 9, so that no pressure can be built · If, however, the main spool 14 in its armed position Ai _2, so is also the path H ₂ Connected via the paths I23 and 12 ₂ to the return line 9, so that no pressure build-up is possible in this position either

When transitioning from the "Rush to" function to

"Stop" the main control piston 13 of the switching valve 11 must drop from its switching position Ru into its middle position '-Mu and the holding valve 25 must also pass from its working position into the rest position.

"Persists in the main spool 13 in its position -aj _1, thus keeping the piston movement, since about & ^5: 'made -HäTteventil 25, the pressure oil supply ^{depressurised: i} wtrd also an initiated following downstroke is.' BeihäKigengebfieberiem main spool 13 in its position of R ₁ 1 is not possible because the pressure oil source 21 is connected to the return 9 both in the position Ri2 and Li _{2 of the main control piston 14.}

Since the controllable holding valve 25 is not actively monitored. it could be that the switching valve 11 and the holding valve 25 do not fall off at the same time. In In this case, the piston would move over the upper limit switch during the rapid-open movement up to the inner stop. A new hub, neither "fast-off" nor "load off", can then be initiated, since for these two movements the main control piston 13 of the switching valve U necessarily in its position must be Ln. The fault must therefore be recognized by the operating personnel and you can only continue working after the malfunction has been eliminated.

In the F i g. 2 and 3, in addition to the symbolic representation of the switching valves 11 and 12, the actual design of the main control piston 13 and 14, respectively, is indicated. In the case of the switching valve 11, the main control piston 13 is hydraulically centered in its central position Mn by means of two end-face rings 26, 26 '. If pressure is applied on both sides via the two pilot valves 15 and 16 (FIG. 2), the rings 26, 26 'are pressed against inner contact surfaces. The main control piston 13 is designed to be correspondingly long, so that it then assumes precisely its central position Mi 1. If only one-sided pressure is applied, the main control piston 13 is axially displaced into the other end position by the pressure application on the piston surface 27 or 27 'of the main control piston 13, with which the rings 26 and 26' are centrally penetrated. The pressurized piston surface 27 or 27 'pushes the main control piston 13 with the opposite ring 26 or 26' into position Ln or Ru, depending on which pilot valve 15 or 16 is activated twice as large as the end faces of the piston surfaces 27, 27 ', so that for a shift into the central position Mn there is twice the shifting force compared to a shift into the switching position Ln or Ru this will become noticeable by getting stuck in the middle position Mn, since this switching position can still be reached by the greater switching force available. In this central position of the main control piston 13, however, no dangerous piston movement of the pistons 4 and 8 is possible, as has already been described above.

Thanks to the control with two separate 4/2 Piloc valves 15 and 16, each switching function the return springs of these pilot valves 15, 16 should be controlled by a spring from one of the two pilot valves 15, 16 broke, that's the next one Movement of pistons 4 and 8 - either moving up or down - can no longer be initiated. The machine goes fault and the error is thus recognized without additional monitoring of the pilot valves 15, 16 is required

The other switching valve 12 is controlled via the pilot valve 19, a 4/3 way valve. As already mentioned, the setting of the central position Mn takes place via two frontal plates 28 and 2S on the main spool 14 acting on springs 17 and 18, similarly As is the case with the switching valve 11 with / the end rings 26, 26 'and the .Druckbeaufschlagung. The centering takes place .jerally through

the spring force. When pressure is applied on one side via the pilot valve 19, a corresponding displacement of the main control piston 14 and thus the corresponding connection of the paths 12 ₍ to 12 <in the manner described above i g. 1 to 3 easily removable.

For this purpose 2 sheets of drawings

Claims (1)

'' '^' '< Claims: '' ^r '-' 11 'Safety control for a hydraulically ^{: vi)} actuable press with at least one rapid traverse ■' - ^ • cylinder 'and one working cylinder over at least ^[ 'Two switching valves are controllable and for this purpose at least one annular space below the piston of one of the '■' Cylinder and at least one space above the piston '■ - "•' optionally '' with a pressure oil source or a " ■ return can be connected or shut off from it, '- the main control piston of a switching valve ■' three switching positions and the Main control piston with a second switching valve at least two switching '■ "has positions marked thereby-15 ή egg; that