EP0241023B1 - Method for controlling automatic cable cranes and hydraulic control system - Google Patents

Abstract

In known automatic cable cranes it is considered to be a disadvantage that, from the safety point of view, vibratory movements of the load pendulum, which can lead to inadvertent clearing of the automatic cable crane, could not be eased by constructional measures. On the other hand, the hydraulic valve layout is made in such a way that sudden displacements of the valves are normally necessary and two-way valves are used as slide or shuttle valves. The leakage losses which are consequently present, in particular in the zero position, can cause dangerous operating states. To avoid these disadvantages, the invention proposes to design the requisite main valves as separate individual valves with dead-time actuation and, in addition, to provide a delay time or a delay displacement so that undesirable vibratory movements of the load pendulum cannot lead to clearing of the automatic cable crane. <IMAGE>

Description

The invention relates to a method for controlling a cable crane machine according to the preamble of claim 1 and a hydraulic control according to the preamble of claim 2.

Such a generic method or the corresponding hydraulic control is known from AT-PS 328 505. This known automatic control of a crane cable car or crane cable machine for load transport, in which a clamping device for locking the cable crane machine and a load pendulum or a load hook connectable with it are provided, has the disadvantage that when the operating position is reached , that is, the position in which the cable crane automat should abseil or lift the load, for safety reasons only a delay time until the actual switching position in which the working cylinders are actuated is provided. This delay time is essential since, when the cable crane machine is at a standstill, at least a certain decay of the vibrations of the suspension cable must first be waited for before the clamping jaw device for clamping the cable crane machine on the suspension cable can be pivoted in and fixed.

However, from a safety point of view it is disadvantageous that the inward and outward movements of the load hook, in particular with the load attached to it, essentially occur in the operating position can trigger vertical vibrations, which can lead to a "disconnection" of the working cylinders and thus the jaws. It therefore appears possible that when the load claws are closed around the load to be picked up, the vibrations of the load hook "unlock" the cable crane machine. Apart from an increased risk of accidents caused by this, it may become necessary that the cable crane automat must first be moved in all cases so that the pressure accumulator provided can be recharged for the renewed loading of the clamping jaws and the other working cylinders. In the worst case, the cable crane machine must even be lowered so that a defined operating state can be achieved again.

Another, unsatisfactory aspect can be seen in the known cable crane machine in that it is designed with a 2-way valve in the form of a shuttle valve that loses pressure oil in the tank during the switching process. Another possible disadvantage is that a slide valve is used which, however, is known to cause leakage losses in the "zero" position, since no absolute tightness is achieved with this type of valve for the high pressures present in the cable crane machines. Leakage losses therefore occur, so that a decrease in the pressure in the corresponding working cylinders with the resulting accident risks appears to be possible. On the other hand, such a slide valve or 2-way valve requires an abrupt actuation when switching, so that aspects of material wear and abrupt changes in the operation of the cable crane machine occur.

Hydraulic controls with a different design for automatic cable cranes are known, for example, from AT-PSn 378 943 and 379 994.

Starting from the above-mentioned prior art, the invention is based on the object of improving the safety-related aspects of the cable crane machine in such a way that even swinging movements on the load hook do not activate of the cable crane machine can bring about with sufficient security and that also with regard to reaching the switching position for loading the working cylinder from the "zero" position, this can be carried out with a high degree of certainty, the structural design permitting a largely controllable, gradual control process , where leakage losses can be largely prevented.

This object is achieved in a generic method by the features of the characterizing part of claim 1 and in a generic control by the features of the characterizing part of claim 2.

An essential idea can therefore be seen in the fact that, in addition to a first delay time to reach the switch position, a further delay time is to be constructively incorporated into the hydraulic control system, which prevents accidental, unwanted disconnection by swinging movements on the load pendulum. In addition, the decoupling of the two main valves for loading and unloading the working cylinders is solved via separate individual valves. These valves, which are advantageously designed as one-way valves with a ball-seat valve design, each assume a position that is complementary to the position of the other valve. This means that when the pressure valve is open, the pressure relief valve is previously closed and vice versa.

In the hydraulic control, the first delay time is advantageously realized by the components of a delay path between the tappet actuating the pressure valve and the corresponding pretensioning of a control piston 18.

The second delay time, which is also considered proportional can be viewed to a second deceleration distance is determined by the distance or time that a control lever needs or has to cover in order to reach the effective range of a control pin that can be actuated by the load pendulum. The control lever itself can, depending on its "zero" position, be designed as a straight-line control rod or with a part-circular recess. The use of separate ball seat valves and their control ensures that leakage losses do not occur even in the case of long idle times in the operating position in which, for example, the working cylinders are pressurized. The construction of the control lever with a pivoting movement in the manner of clock hands around its axis or with a slight oblique deflection against the axis allows the control lever to be movable from an operative connection with the shifting gate when the load pendulum is retracted reliably and a corresponding release mechanism for the clamping jaws is actuated can gradually return to its zero position under the pre-tensioned control piston of the valves.

The working cylinders for pivoting the clamping jaws or actuating the clamping jaws themselves are expediently coupled to one another in such a way that an overflow to the working cylinder of the clamping basin is only released after the reliable engagement and pivoting-in, so that the fixing process only then begins. This ensures that oscillating movements of the suspension cable have at least largely subsided and the clamping jaws can thus be reliably fixed on the suspension cable. Without requiring any further mention, the cable crane automat according to the invention can alternatively be equipped for single-cable operation, two-cable operation or three-cable operation.

The second delay time which is essential to the invention can therefore be defined as the time which the control lever requires, to get from the switch position to a control pin that is operatively connected to the load pendulum. During this time, an uncontrolled activation of the cable crane machine is not possible for safety reasons.

The invention therefore has the advantages that the shift lever can act on a switching piston of the valves by the control via a shift gate so that the pressure relief valve is always closed and the pressure valve subsequently opens in order to enable the working cylinder to be acted upon safely via the opened valve . This process does not start suddenly, as with conventional control valves, but takes place gradually, so that pressure losses are avoided. The release of the shift lever from its locked position on the shift gate by a lateral movement at an angle to its axis is effected via inclined surfaces of a linkage and the control bolt, so that the shift lever is pressed from its position on or in the shift gate and both due to the pressure of the pressure fluid and a compression spring is returned to its initial position (zero position). The shift lever can therefore only be taken from the shift gate when the operating position of the cable crane machine, which is understood to mean the place at which the load is to be picked up or roped, is only taken back when the shift gate is back in its right due to the movement of the timer piston Has reached the end position. In this end position, the shift lever is pressed by a spring in front of the front face of the shift gate.

A major advantage of the hydraulic control is that the entire control is housed in a closed, compact block, which also includes the mechanical components. This makes it easier to repair reached. An additional rope break protection can also be easily retrofitted. It is also achieved that the switching operations can only take place when the pressure accumulator is charged and without further control of a pressure switch. The time between the unlocking of the load hook or the clamping on the supporting cable and between the earliest possible relocking or releasing the clamping on the supporting cable is carried out via at least one adjustable throttle, so that an automatic setting of the switching time is realized. The invention therefore makes it possible to provide an optimal hydraulic control for a cable crane machine which has to be clamped on the supporting cable for lowering or lifting a load hook, during which time the load hook lock is opened. As long as the rope crane is moving on the suspension rope and the rope pulleys on the suspension rope rotate, there should of course be no jamming on the suspension rope. Only when the automatic cable crane has reached the point at which loading or unloading takes place (operating position), should the built-in hydraulic control clamp the lifting cable and unlock the load hook, so that after loading or unloading and after retraction of the load hook to lock it again and to release the clamp on the suspension cable.

Advantageous developments of the invention are claimed in the subclaims.

Fig. 1

ein schematisches Flußdiagramm durch die Hydraulikleitungen und Anschlüsse mit der "Null"-Stellung eines Steuerhebels mit einem geöffneten Druckentspannungsventil und der Darstellung der Verzögerungsstrecke V 1;

Fig. 2

das schematische Flußdiagramm nach Fig. 1 mit dem Schalthebel in Schaltstellung bzw. mit strichpunktiertem Linienzug in Betätigungsstellung über einen Steuerbolzen, wobei die Verzögerungsstrecke V2 dargestellt ist;

Fig. 3

eine Schnittdarstellung längs der Linie III-III nach Fig. 2 durch einen Teil der mechanischen Schaltmechanismen mit einer Stellung des Schalthebels, in der dieser von einer Schaltkulisse gesteuert wird, wobei dies einer Phase des noch nicht eingefahrenen Lasthakens entspricht;

Fig. 4

eine vergleichbare Stellung nach Fig. 1, wobei der Steuerhebel sich in Fahrt- bzw. Ruhestellung oder "Null"-Stellung befindet;

Fig. 5

eine leicht geänderte Darstellung des Beispiels nach Fig. 1 mit der hydraulischen Steuerung während der Fahrt eines Seilkrans und vor Erreichen des Betriebsdruckes.

The invention is explained in more detail below with the aid of schematic hydraulic diagrams or cross sections through the mechanical control device. Show it:

Fig. 1

a schematic flow diagram through the hydraulic lines and connections with the "zero" position of a control lever with an open pressure relief valve and the representation of the delay line V 1;

Fig. 2

the schematic flow chart of Figure 1 with the shift lever in the switching position or with dash-dotted lines in the actuating position via a control pin, the delay line V2 is shown.

Fig. 3

a sectional view along the line III-III of Figure 2 by part of the mechanical switching mechanisms with a position of the shift lever in which this is controlled by a shift gate, which corresponds to a phase of the not yet retracted load hook.

Fig. 4

a comparable position of Figure 1, wherein the control lever is in the travel or rest position or "zero" position.

Fig. 5

a slightly modified representation of the example of FIG. 1 with the hydraulic control while driving a cable crane and before reaching the operating pressure.

The hydraulic control 1 serves to clamp an automatic cable crane for lowering or lifting a load hook, which is not shown in the drawings, on the supporting cable and to open the lock of the load hook during this time.

As long as the rope crane moves along the wire rope and If the rope pulleys turn on the suspension rope as a result, jamming on the suspension rope should naturally be prevented or only take place in an emergency, for example using a rope break safety device. Only when the automatic rope crane has reached the point at which loading or unloading takes place, i.e. the operating position, should the built-in hydraulic control clamp the lifting rope and unlock the load hook, after loading or unloading and after Retract the load hook to lock it again and release the clamp on the suspension cable. During the journey, an oil pump 2 continuously pumps the hydraulic fluid, which in the example is a pressure oil, from the tank 3 into the compactly designed control block. In the example according to FIG. 2, the control block essentially comprises all lines, time cylinders and valves as well as the mechanical control mechanisms in order to ensure the full function of the automatic cable crane.

In the example according to FIG. 1, the pressure oil from the pump 2 reaches a pressure accumulator via a high pressure filter 4 and a check valve 5. The pressure oil delivered into the pressure accumulator 6 has the primary function of applying the appropriate pressure oil to the working cylinders 22 to 24 when the operating position is reached. The pressure accumulator 6 is connected to a pressure valve 7. This pressure valve 7 is designed as a check valve and has a valve ball 8 which, in the position shown in FIG. 1, bears against the valve seat 29, so that the valve is closed.

When a set storage pressure in the pressure accumulator 6 is reached, the pressure oil flows through a pressure limiting valve 8 on the one hand into a time cylinder 10 and on the other hand through a flow-regulating throttle valve 14, the latter being in reflux connection with the tank 3.

The pressure oil pumped into the time cylinder 10 pushes its piston 9 to the right and thus moves the piston rod 11 and the shifting link 16 articulated thereon against the force of a spring 12 to the right. 1 shows the "zero" position of the piston 9 or of a shift lever or shift finger 15 which can be controlled via the shift link 16.

When pressure is applied to the piston 9, the piston 9 is moved to the right into a specific end position, which is not shown. In this end position, the piston releases an overflow 13, so that the pressure oil which is still pumped into the time cylinder 10 can flow back into the tank 3. In the right end position of the piston 9, the shift lever 15 engages with its lower end 50 in engagement with the front edge 17 of the shift link, the engagement from a groove 47 (FIG. 3) on the front edge 17 being effected by the force of a spring 46.

When the operating position of the cable crane machine is reached, the shift lever 15 is in the “zero” position shown in FIG. 1, but the front edge 17 of the shift link 16 engages at its lower end 50. The piston 9 is in its right end position. When this operating position is reached, the pressure oil supply in the time cylinder 10 now stops, so that the spring 12 gradually displaces the piston 9 to the left and the pressure oil is thereby conveyed back from the time cylinder 10 via the throttle valve 14 into the tank 3.

In order to provide a first delay time when the operating position of the cable crane machine is reached for safety reasons, there is a delay path V1 between the valve ball 28 and the valve tappet 30 actuating it constructively provided.

In the position shown in FIG. 1, the pressure relief valve 20 for returning the pressure oil from the working cylinders 22 to 24 into the tank 3 is open in this position, or is closed again after relieving the pressure on the working cylinders.

If the control lever 15 is now moved from its "zero" position according to FIG. 1 with engagement on the front edge 17 of the switching link 16 into the "switching position" according to FIG. 2, the delay distance V1 must first be covered. The valve tappet 30 which is decisive for this is connected to the control piston 18, through which the switching lever 15 can be guided, for example, so that a force-fitting actuation of both elements is possible. The control piston 18 is also biased toward the right by a spring 19. As a result, this spring force 19 acts against a force acting through the switching link 16 on the control lever 15 and directed to the left.

1, the control lever 15 is moved from its "zero" position into the position of the shift lever 15 shown in solid line in FIG. 2 through the shift gate. The shift lever 15 performs a clockwise movement about its axis 48, so to speak. Before opening the valve 7 it is ensured in any case that the pressure relief valve 20 is closed. This is most suitably done with a minimal movement out of the "zero" position, so that almost the entire deceleration distance or the first deceleration time resulting therefrom taking into account the spring characteristic 19 is available in terms of safety. This first delay can vary depending on the design of the individual components between approx. 2 to 30 seconds.

The first delay time can therefore be defined as the period of time that the control lever 15 needs to get from its "zero" position to the "switching position". From a safety point of view, this first delay time primarily serves to calm the suspension cable after the operating position of the cable crane machine has been reached. Only when the pressure valve 7 is open, after the first delay time has elapsed, for example, the working piston 22 of the pivoting cylinder is pressurized with pressure oil, the clamping jaw cylinder itself being actuated only after an overflow 26 has been reached.

In the operating or working position shown in FIG. 2, pressure oil therefore flows from the pressure accumulator 6 via the valve 7 to the working cylinders 22 to 24 and there causes the automatic cable crane to be clamped to the supporting cable and the load hook to be unlocked. At the same time, this pressure oil reaches the second valve 20, which is still blocked, however, since it only has the function of depressurizing the working cylinders when the load hook is retracted.

The time that should elapse between reaching the operating position of the cable crane machine and releasing the clamping can therefore be regulated by means of the adjustable throttle valve 14.

As soon as the load hook (not shown) moves back into the cable crane machine after loading or unloading, the load hook triggers the control pin 40 or trigger via a shift linkage 41 and a slope 43 (FIG. 3, FIG. 4). That is, by shifting the shift linkage 41 upward against a spring 42 (FIG. 3), the slope 43 comes into sliding engagement with a slope 44 on the control piston 40 and pushes it against a spring 45 to the right. The shift lever 15 guided according to FIG. 3 on the front edge 17 of the shifting link 16 is pressed over the ring surface 52 of the control bolt 40 to the right into a certain oblique position against the spring force 46. The guide opening 49 within the control piston is held so that the slight inclination from the vertical to the axis 48 can still be realized without the control lever 15 jamming in the shifting link or the control piston 18.

By moving the control pin 40, which is slidably movable in a guide 51, for example of the housing, the lower end 50 of the control lever 15 is brought out of engagement with the front edge 17 of the switching link 16 and is inserted into a groove 47 of the switching link. When this position according to FIG. 4 or the dash-dotted position according to FIG. 2 is reached, the spring force 19 causes the control piston to shift to the right, so that the valve 7 is first closed and the pressure relief valve 20 is gradually opened so that the working piston 22 up to 24 can be relieved of pressure.

In this position, the pressure oil can flow back into the tank 3 from the working cylinders via the opened valve 20 and a return line 31. The clamping of the cable crane machine on the suspension cable is released and the load hook is locked again.

The cable crane machine is now ready to drive again. While driving on the oil pump 2, the partially emptied pressure accumulator 6 is filled again and then the timer cylinder 10, so that the shift lever 15 returns to a standby position in which its "zero" position according to FIG. 1 with system the front edge 17 of the shift gate 16 is reached.

A second delay time or a second delay line V2 is structurally provided in order to get a handle on vibration-like inward and outward movements of the load hook or load pendulum cylinder when the rope crane machine reaches the operating position. This delay section is necessary from a safety point of view, since, for example, in the starting phase of lowering a load of the load hook via the shift linkage 41, it could cause a shift movement, as shown in FIG. 4. This would lead to the locking of the valve 7 and the opening of the valve 20 and thus the release of the jaw cylinder 23, which could have catastrophic consequences. In order to avoid this, the return of the shift lever 15 (FIG. 2) from the solid position to the dash-dotted position in a clockwise direction via the throttle valve 14 is designed so that the shift lever 15 is the dash-dotted position in which the actuation of the working cylinder 22 to 24 is stopped, only reached after a second delay time or a corresponding time delay distance V2. Only then is it possible to disengage from the position shown in FIG. 3 into the position shown in FIG. 4.

5, the same reference numerals have the same meaning as in the preceding examples, the overall function also being designed accordingly.

Claims (8)

1. Method of controlling an automatic cable crane, in which, when the operating position has been reached, the pressurisation of the working cylinders (22, 23, 24) for a clamping device hydraulic fluid in accordance with the operation is released only after a delay time, and the return flow of the hydraulic fluid from the pressurised working cylinders (22, 23, 24) into the hydraulic fluid tank (3) is subsequently carried out by retracting the load hook, characterised in that the release of the return flow of the hydraulic fluid from the pressurised working cylinders (22, 23, 24) is carried out with a first time delay (V1) after the pressurisation of the working cylinders (22, 23, 24) has been blocked, and in that the tripping for the release of the return flow is provided by a load or swinging of the load hook after a second delay time (V2).
2. Hydraulic control for an automatic cable crane, which control pressurises the working cylinders (22, 23, 24) with hydraulic fluid from an accumulator (6) via a pressure valve (7) in the operating position of the automatic cable crane after an adjustable first delay time (V1), having a pressure relief valve (20) for returning the pressure fluid from the working cylinders (22, 23, 24) into a tank (3), and having a switch lever (15) for actuating at least the pressure valve (7), the switch lever (15) being operatively connected to a time switch cylinder (10), characterised in that the pressure valve (7) and the pressure relief valve (20) are constructed as separate one-way directional valves and can be moved via a prestressed shift piston (18), taking the first delay time (V1) into consideration, into a complementary opening position of the one valve and a closing position of the other valve in each case, in that a shifting gate (16), coupled to the time switch cylinder (10), is provided to control the switch lever (15), it being possible for the switch lever (15) to be moved by a control bolt (40) out of operative connection with the shifting gate (16), and in that an operative connection is effected between the control bolt (40) and a shift linkage (41, 43), which can be actuated by the load pendulum, for "clearing" at least one working cylinder (22, 23, 24) only after an adjustable second delay time (V2) has elapsed.
3. Hydraulic control according to Claim 2, characterised in that the switch lever (15) is forced away by the control bolt (40) to the side of the shifting gate (16) by retraction or swinging of the load hook, such that the switch lever (15) passes into its original starting position again by means of the springprestressed shift piston (18), the pressure valve (7) closing and the pressure relief valve (20) opening so that the hydraulic fluid can flow back into the tank (3) from the working cylinders (22 to 24).
4. Hydraulic control according to Claim 2 or 3, characterised in that the shift piston (18), which is prestressed in the direction of the pressure relief valve (20), is constructed on the side of the pressure valve (7) in such a way that the hydraulic fluid continues to support a spring (19) of the shift piston (18) in the direction of pressure until the pressure relief valve (20) is opened.
5. Hydraulic control according to one of Claims 2 to 4, characterised in that the switch lever (15) is mounted in such a way that, about its axis (48), it can carry out both a pivoting movement about the axis and a radial deflection relative thereto.
6. Hydraulic control according to one of Claims 2 to 5, characterised in that, despite prestress via a spring (46), the switch lever (15) in its "zero" position is guided in a sliding manner in a recess (47) of the shifting gate (16) during displacement of the shifting gate (16).
7. Hydraulic control according to one of Claims 2 to 6, characterised in that, when the automatic cable crane has reached the operating position, the time switch cylinder (10) has displaced the shifting gate (16) in such a way that the switch lever (15) rests nonpositively against a carrier surface (17) of the shifting gate as a result of the spring force (46).
8. Hydraulic circuit according to one of Claims 2 to 7, characterised in that the first and second delay times are adjustable via a common (14) or two separate throttle valves.

Images