EP0283694A1 - Locking device for fluid actuator - Google Patents

Abstract

1. Braking device for pressure medium cylinders, especially cylinders (26) without a piston rod, having a braking element (9, 9') which can be operated on by pressure medium, this pressure medium operation being monitored by a switch valve (8, 8'), characterised in that between a pressure medium source (1) and the switch valve (8, 8'), constructed at least as a 3/2-way valve, there is arranged a pressure medium reservoir (4) which can be charged by means of a non-return valve (3) from the pressure medium source, in that the pressure of the pressure medium source (1) acts on a pressure monitor (5) which, when a first high pressure threshold is not reached, switches the switch valve (8, 8') so that it opens an otherwise closed connection from the pressure medium reservoir (4) to the brake element (9, 9'), in that a spring-loaded cylinder (13), acted on by the pressure medium reservoir (4), is provided which, when acted on by a pressure which falls below a second mean pressure threshold, activates a mechanical movement lock (14, 16) arranged in parallel to the braking element (9, 9'), and in that the braking element (9, 9') is designed to maintain the nominal load of the pressure medium cylinder until its actuation pressure falls below a third, low pressure threshold.

Description

The invention relates to a braking device for pressure medium cylinders, in particular rodless cylinders, with a brake element which can be tightened by means of pressure medium application and whose pressure medium application is monitored by a switching valve.

Such braking devices are shown, for example, in EP-A 104 364 for rodless cylinders, the braking member being arranged integrated in the power take-off member.

In such cylinders, it is also known to provide clamping grooves on the outside of the cylinder body, to which stroke-dependent switches can be adjustably connected.

The known brake devices mentioned have the defect to solve in the event of an undesired loss of pressure, which often cannot be permitted for safety reasons. To avoid this deficiency, it is known to design the braking members as spring-loaded brakes, that is to say to apply them with spring force and to release them by means of pressure medium. Here, however, it is difficult to accommodate springs that are sufficiently strong with a sufficient stroke in the cramped installation spaces; in addition, these highly stressed springs can weaken or break, causing the braking element to fail.

It is therefore an object of the invention to provide a braking device to create the type mentioned, which has a safe function with a simple structure.

This object is achieved according to the invention in that between a pressure medium source and the 3/2-way switching valve, a pressure medium accumulator which can be charged via a check valve from a pressure medium source is arranged in such a way that the pressure of the pressure medium source acts on a pressure switch which, when the pressure falls below a first, high Pressure threshold switches the switching valve to open an otherwise closed connection from the pressure medium store to the brake member, that a spring-loaded cylinder from the pressure medium store is provided, which activates a mechanical movement block arranged parallel to the brake member when a pressure exceeding a second, medium pressure threshold is applied, and that Braking member is designed to hold the nominal load of the pressure medium cylinder until it falls below a third, low pressure threshold of its pressure.

This ensures that in the event of an undesired pressure drop or failure of the pressure medium source, the brake member is initially pressurized from the pressure medium store to actuate it, this pressure also drops inadmissibly, the spring-loaded cylinder switches on the mechanical movement lock, for which purpose the spring of the spring-loaded cylinder only has a low output must muster; the pressure medium cylinder is then locked in position by the mechanical movement lock and cannot carry out any unwanted movement.

According to the further invention, advantageous design options for the braking device can be found in the subclaims.

• Fig.1 u. 2 zwei unterschiedliche Ausführungsformen in schematischer Darstellung,
• Fig.3 eine Ergänzung der Bremseinrichtung mit einer direkten Bremssteuerung in ebenfalls schematischer Darstellung,
• Fig.4 ein Funktionsdiagramm und
• Fig.5 A bis D ein Kraftabnahmeorgan eines kolbenstangenlosen Zylinders mit integrierter Bremseinrichtung in drei Ansichten und einem Schnittbild.

In the drawing, exemplary embodiments of braking devices designed according to the invention are shown, namely

• Fig.1 u. 2 shows two different embodiments in a schematic representation,
• 3 shows a supplement to the braking device with a direct brake control, likewise in a schematic representation,
• 4 shows a functional diagram and
• 5 A to D a force take-off element of a rodless cylinder with an integrated braking device in three views and a sectional view.

According to FIG. 1, a pressure medium connection 2 leads from a pressure medium source 1, here a compressed air source, through a check valve 3 to a pressure medium reservoir 4 designed as a container. A pressure switch 5 is connected to the pressure medium connection 2, which is above a relatively high spring 6 by an adjustable spring 6 adjustable pressure threshold in the pressure medium connection 2 closes a switch 7 and keeps it open below this pressure threshold. A switching valve, designed as a solenoid valve 8 and representing a 3/2-way valve, is connected to the pressure medium accumulator and connects the pressure medium accumulator 4 with a pressure medium connection 10 leading to braking elements 9 in the de-energized state; in the de-energized state, the solenoid valve 8 blocks this connection and keeps the pressure medium connection 10 depressurized, for example in the illustrated pneumatic system, vented to the atmosphere. The switch 7 is arranged in an electrical connection 11 from a current source symbolized only by a plus sign to the excitation coil of the solenoid valve 8. Furthermore, the pressure chamber 12 of a spring-loaded cylinder 13 is connected to the pressure medium reservoir 4, the piston rod 14 of the spring rod 15 when the force falls below a second, average pressure threshold in the pressure chamber 12 extends. In the retracted state, the piston rod 14, which represents a locking pin, ends in front of a perforated strip 16 located in front of the spring-loaded cylinder 13; in the extended state, the piston rod 14 can engage in the holes 17 in the perforated strip 16. The piston rod 14 thus forms, together with the perforated strip 16, a mechanical, switchable movement lock 14, 16.

The braking device described above is arranged on a pressure medium cylinder (not shown in FIG. 1) with at least one fixed part and one part that is movable under pressure medium in such a way that the check valve 3, the pressure monitor 5, the pressure medium accumulator 4, the solenoid valve 8, the braking members 9 and the Spring cylinder 13 on one and the perforated strip 16 on the other of the two parts. In a rodless cylinder with a mostly sled-like force-absorbing element, the perforated strip 16 is expediently fixed, and in the case of a conventional piston rod cylinder, the perforated strip 16 can be arranged in a movable manner with the piston rod. The braking members 9 are constructed in the usual way as a friction brake; they can, as can be seen from the above-mentioned EP-A 104 364, each have a cylinder or bellows which can be pressurized by the pressure medium connection 10 and which, when pressurized, has a friction element, in particular a brake shoe or presses a brake lining onto the other part of the pressure cylinder which is relatively displaceable for this purpose.

In addition to the brake device shown in FIG. 1, the pressure medium cylinder can be equipped with a further, customary brake, for example according to EP-A 104 364 mentioned, which is used as a service brake in normal operation of the pressure medium cylinder.

The braking device according to Fig. 1 acts as follows:

As long as the pressure medium source 1 has sufficient pressure, the switch 7 is closed and, if the power source is functioning, that Solenoid valve 8 thus excited. The pressure medium reservoir 4 is filled by the check valve 3 from the pressure medium source 1, but the energized solenoid valve 8 keeps the braking members 9 depressurized and thus released. The spring-loaded cylinder 13 is acted upon from the pressure medium reservoir 4, so that its piston rod 14 is retracted and out of engagement with the perforated strip 16. If the pressure at the pressure medium source 1 drops due to any damage, the switch 7 of the pressure switch 5 opens when the pressure falls below a first, still relatively high pressure threshold and thus interrupts the excitation of the solenoid valve 8. The solenoid valve 8 therefore switches to the switch position shown um, whereby it separates the braking members 9 from the atmosphere and instead connects to the pressure medium accumulator 4. The braking elements 9 are therefore pressurized from the pressure medium store 4 and tighten, so that the pressure medium cylinder is braked in its current position. Since the pressure drop in the pressure medium source 1 via the check valve 3 means that there is no further pressure make-up in the pressure medium reservoir 4, a compensating pressure is established between the pressure medium reservoir 4 and the pressurized spaces of the braking members 9, which, however, is considerably higher than the pressure level by appropriately dimensioning the volume of the pressure medium reservoir 4 which is required to safely brake the pressure medium cylinder under its nominal load. The spring-loaded cylinder 13 remains in its tensioned position, the piston rod 14 thus remains out of engagement with the perforated strip 16.

If a leak is present or occurs on the pressure medium reservoir 4 or the rooms connected to it, the compensating pressure prevailing in these rooms gradually drops. If the pressure falls below a second, medium pressure threshold, the storage spring 15 of the spring-loaded cylinder 13 pushes out the piston rod 14 so that it engages with the perforated strip 16. In general, the piston rod 14 will not yet engage in one of the holes 17 of the perforated strip 16, but rather on that Spring surface 13 facing surface 18 of perforated strip 16 stand up. At this medium pressure threshold mentioned, the application pressure is still sufficient to securely apply the braking elements 9. If the leak continues, the pressure in the pressure medium reservoir 4 and the spaces connected to it further decreases. As soon as this pressure falls below a third, relatively low pressure threshold, the application force of the braking elements 9 is no longer sufficient to brake the pressure medium cylinder when it is loaded with a nominal load, the piston rod or the force-taking elements of the pressure medium cylinder therefore begin to slip under load with a nominal load. During this slipping, the perforated strip 16 shifts in its longitudinal direction relative to the spring-loaded cylinder 13, so that one of the holes 17 soon reaches the piston rod 14 and the piston rod 14 thus snaps into this hole 17, as shown in FIG. At a slight, further displacement, the perforated strip 18 comes into contact with the piston rod 14 with the wall of the hole 17 and is thereby positively prevented from further displacement. The pressure medium cylinder is thus locked in a form-fitting manner, so no further movement can take place. If, by chance, the piston rod 14 immediately engages in one of the holes 17 when it is extended, the aforementioned slipping of the pressure medium cylinder is of course not required; the pressure medium cylinder is locked in a form-fitting manner immediately without slipping.

The storage spring 15 is only slightly loaded when the piston of the spring storage cylinder 13 is suitably dimensioned, and can therefore be designed to be fatigue-free and unbreakable.

In a modification of the above-described embodiment, it is possible to place a further switch 19, indicated only by dashed lines, in the electrical connection between the current source and the switch 7, possibly also in the connection 11: With an intact pressure medium and current source, this switch 19 can be used for operational actuation of the braking members 9 serve, it is in this So if no further service brake is required. To release or hold the brake members 9, the switch 19 is to be closed, the excitation of the solenoid valve 8 keeps the brake members 9 depressurized and thus released, while when the switch 19 is opened the excitation of the solenoid valve 8 is interrupted and the brake members are pressurized to brake will. The switch 19, as is customary for service brakes, can be switched by any stops or a control program for the pressure medium cylinder.

2 shows a braking device corresponding to that of FIG. 1, but the braking members are designed as a dual-circuit brake with the braking members 9 and 9ʹ for one braking circuit each, this dual-circuiting serves to further increase operational safety. The parts corresponding to FIG. 1 are given the same reference numerals in FIG. 2 and therefore require no further explanation. 1, a pressure medium connection 20 leads from the solenoid valve 8 to an inlet of a 5/3-way valve 21, which is stabilized in its middle switching position by two springs 22. The two output connections of the directional valve 21 are each connected to the braking members 9 and 9ʹ via a pressure medium connection 10ʹ or 23. From the pressure medium connections 10ʹ and 23 branch channels lead to the end-side loading chambers of the directional control valve 21, which switch this directional control valve 21 into one of its two end positions when the pressure medium is applied unevenly. In the middle switching position shown, the directional control valve 21 connects the pressure medium connection 20 to the two pressure medium connections 10ʹ and 23, so that during braking operations, as described above for FIG. 1, both brake circuits are pressurized and thus the braking members 9 and 9 wurden have been applied. If one of the two brake circuits fails due to a leak, no pressure can build up in it during braking, the directional control valve 21 is therefore pressurized on one side via the branch channels and switches to one of its lateral limit switch positions in which it connects the pressure medium connection 20 connects alone with the intact brake circuit for the braking elements 9 or 9ʹ, while the other, defective brake circuit is kept depressurized. The function of the braking device is thus ensured even in the case of a defective brake circuit. Otherwise, the function of the braking device according to FIG. 2 corresponds to that according to FIG. 1.

To use the braking elements provided for the braking device also for the service braking of the pressure medium cylinder required in normal operation, an arrangement according to FIG. 3 can be provided in a further modification: In FIG. 3, the check valve 3, the pressure switch 5, the air container 4 and the spring accumulator 13 combined into a structural unit, which is symbolized by a square 24, to which on the one hand the pressure medium source 1 and on the other hand a solenoid valve 8 'is connected. The line 10 or 20 extends from the solenoid valve 8ʹ according to FIG. 1 or 2. 1 and 2, the solenoid valve 8ʹ in the excited state does not connect the pressure medium connection 10 or 20 to the atmosphere, but to a further solenoid valve 25; in the de-energized state, the connections and functions described in FIGS. 1 and 2 are effected. The solenoid valve 25 is designed as a 3/2-way valve, in the unexcited state it connects a pressure medium source 1ʹ, which can correspond to the pressure medium source 1, to the solenoid valve 8ʹ, in the excited state it keeps the connection to the solenoid valve 8ʹ unpressurized. It thus follows that with an intact pressure medium source and power supply by means of the solenoid valve 25 direct control of the pressurization of the braking members is possible, the braking members being actuated when the solenoid valve 25 is not energized and the braking members released when the solenoid valve 25 is energized.

The function of the braking device according to FIGS. 1, 2 or 3 is illustrated in the diagram according to FIG. In FIG. 4, p3 means the pressure applied to the braking elements, that is to say the pressure prevailing in the pressure medium connection 10 or 20, p2 the pressure in the pressure medium reservoir 4, p _v the pressure of the pressure medium source 1 and I the excitation current for the solenoid valve 8 or 8ʹ. On the abscissa the time lapse is plotted. During the period T, the pressure medium and the current source are intact. During this period T takes place during the period between the times t₁ and t₂ a controlled by closing the switch 19 release process, the solenoid valve 8 picks up during this period, so that the pressure p₃ drops and the braking members 9 release. At the time t₃ there is a new release process, which should continue until the time t₄. At time t₅, however, the pressure medium source 1 fails, its pressure drops rapidly according to p _v and the switch 7 of the pressure monitor 5 opens immediately. The solenoid valve 8 drops and acts on the braking elements 9 from the pressure medium accumulator 4, so that its pressure, as can be seen from the pressure curve of the p₂, drops slightly; the drop in pressure is sufficient for safe braking. At the time t₆ the braking members 9 should also leak, so that their pressurization pressure together with the pressure of the pressure medium reservoir 4, as can be seen from the pressure profiles p₃ and p₂, begins to drop. At time t₇, the pressure in the pressure medium reservoir 4 has dropped to a value at which the spring-loaded cylinder 13 responds and the piston rod 14 extends; however, the braking members 9 are still securely applied. If there is a further loss of pressure, the pressure drops below the pressure in the braking elements 9 at which they begin to slip under load with the nominal load of the pressure medium cylinder, at the latest immediately after this point in time, the piston rod 14 engages in a hole 17 in the perforated strip 16 and positively locks the pressure medium cylinder . It can thus be seen that if the pressure medium source fails, the frictional braking elements 9 are actuated and if there is a subsequent pressure loss due to leakage, a positive locking takes place. This provides great security against undesired movements for the pressure medium cylinder. At the time t die the pressure medium source 1 becomes pressurized again, the pressure switch 5 soon closes its switch 7 so that the solenoid valve 8 is energized again between the time t₉ to t₄, the braking members 9 during this time so be kept depressurized. When pressure builds up in the pressure medium accumulator 4, the spring-loaded cylinder 13 simultaneously pulls its piston rod 14 out of the hole 17 in the perforated strip 16, so that the positive locking is released and the pressure medium cylinder is again free of movement. At time t₄ the switch 19 is opened, the excitation of the solenoid valve 8 is thus interrupted and the braking members 9 are pressurized for braking from the recharged pressure medium reservoir 4.

In FIGS. 5 AC, a rodless cylinder 26 is indicated in front view, top view and side view with dashed lines, which cylinder is provided with a slide or force output element 27 shown in solid lines. The force output element 27 includes a braking element, as is known, for example, from EP-A mentioned at the beginning. From FIG. 5 B, which shows a section along line AB in FIG. 5 A, it can be seen that the force output element 27 contains cavities 28 which serve as pressure medium stores. Furthermore, a recess 29 for receiving a check valve and a further recess 30 for receiving a pressure switch 31 are provided, the pressure switch 31, in contrast to FIG. 1, is designed as a 3/2-way valve without a switch 7 and thus also fulfills the function of the solenoid valve 8 Fig. 1. The spring-loaded cylinder 13 with the storage spring 15 and the piston rod 14 is arranged in the center of the force-output member 27, the piston rod 14 extends transversely to the longitudinal direction of the cylinder 26. Finally, a solenoid valve 32 is provided, which corresponds to the solenoid valve 25 according to FIG. The above-mentioned functional parts are connected by means of bores and channels running in the walls of the power output member 27. On the outside of the cylinder 26 there are clamping grooves 33, one of which is clamped with a stop 35 by means of a clamping device 34. The stop 35 protrudes only when the piston rod is extended in its path of motion when the force output element 27 is moving. Overall, this results in a rodless cylinder which, with little additional effort and little enlargement of the required Installation space in addition to a service brake has a frictional braking device, which acts in emergencies, with a form-fitting emergency stop held adjustably by the clamping device 34.

The braking device is also suitable for hydraulic pressure medium cylinders, the pressure medium accumulator must be designed accordingly and return lines must be provided instead of venting.

Reference symbol list

1.1ʹ pressure source
2 pressure medium connection
3 check valve
4 accumulators
5 pressure switches
6 spring
7 switches
8.8ʹ solenoid valve
9.9ʹ braking element
10.10ʹ pressure fluid connection
11 connection
12 pressurization room
13 spring-loaded cylinders
14 piston rod
15 spring
16 perforated strip
17 holes
18 surface
19 switches
20 pressure medium connection
21 way valve
22 spring
23 Pressure fluid connection
24 square
25 solenoid valve
26 cylinders
27 power transmission element
28 cavity
29 recess
30 recess
31 pressure switches
32 solenoid valve
33 clamping groove
34 clamping device
35 stop

p³ loading pressure
p² pressure
p _v pressure
I excitation current
T time span
t₁ time
t₂ time
t₃ time
t₄ time
t₅ time
t₆ time
t₇ time
t₈ time
t₉ time
AB line

Claims (8)

1. Braking device for pressure medium cylinders, in particular rodless cylinders (26), with a brake element (9, 9ʹ) which can be tightened by pressure medium application, the pressure medium application of which is monitored by a switching valve (8,8ʹ), characterized in that between a pressure medium source (1) and the A switching valve (8, 8 ') designed at least as a 3/2-way valve is arranged in a pressure medium accumulator (4) which can be charged via a check valve (3) from the pressure medium source (1) such that the pressure of the pressure medium source (1) acts on a pressure monitor (5). which, when falling below a first, high pressure threshold, switches the switching valve (8,8ʹ) to open an otherwise closed connection from the pressure medium accumulator (4) to the braking element (9,9ʹ), that a spring-loaded cylinder (13) loaded from the pressure medium accumulator (4) is provided which, when subjected to a pressure below a second, medium pressure threshold, is a mechanical one, parallel to the braking element (9.9ʹ) lel arranged movement lock (14,16) activated, and that the braking member (9.9ʹ) is designed to hold the nominal load of the pressure medium cylinder until it falls below a third, low pressure threshold of its pressure. 2. Braking device according to claim 1, characterized in that the movement lock is designed as a stop (14, 16 or 35) switchable by the spring-loaded cylinder (13). 3. Braking device according to claim 2, characterized in that the stop a movable from the spring-loaded cylinder (13), optionally formed from the piston rod (14) locking pin and has a multiplicity of stop surfaces arranged offset in the stroke direction of the pressure medium cylinder and possibly combined in a perforated strip (16), optionally walls of bores (17). 4. Braking device according to one of claims 1 to 3, characterized in that the pressure switch (5) has an excitation of the switching valve designed as a solenoid valve (8,8ʹ) when the pressure drops below the first pressure switch (7). 5. Braking device according to claim 4, characterized in that the switch (7) is another switch (19) electrically connected upstream. 6. Braking device according to claim 4, characterized in that the switching valve (8ʹ), the braking member (9) alternately to the pressure medium accumulator (4) or another, the connection to a pressure medium source (1ʹ) or a return control switching valve (25) connects . 7. Braking device according to claim 1, characterized in that two pneumatically separate braking members (9 and 9ʹ) are provided, which are connected via a 5/3-way valve (21) to the switching valve (8,8ʹ), the 5 / 3-way valve (21) is acted upon in the opposite switching directions by the pressures of the two braking elements (9 and 9ʹ), in the limit switch positions the brake element (9 or 9ʹ) with its pressure in the switching direction and both in its spring-stabilized, middle switching position Brakes (9 and 9ʹ) connects to the switching valve (8,8ʹ). 8. Braking device according to one or more of the preceding claims, for a rodless cylinder (26), in the power take-off member (27) of the braking member (9,9ʹ) is integrated, thereby characterized in that the switching valve (8,8ʹ), the pressure medium accumulator (4) and the spring-loaded cylinder (13) are also arranged integrated in the power take-off element (27).

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