EP0287807B1 - Safety device for the electric winch of a building site lift - Google Patents

Abstract

The safety device has an essentially rectangular pivoting frame (3) which is arranged below the rope drum (1) and can be pivoted on one side about a pivot axis (4) parallel to the rope-drum axis (A) and through which the rope (17) is passed. Rigidly connected to the pivoting frame (3) is an actuating member (9) which, as a function of the position of the pivoting frame (3), acts on a direction-sensitive limit switch (12) in such a way that, in the operating position of the pivoting frame (3), the limit switch (12) releases the power supply to the winch motor for both directions of rotation and, in the raised position of the pivoting frame (3), in a second switch position, releases the power supply only for the downward direction of rotation. On its side remote from the pivot axis (4), the pivoting frame (3) has a roller (6) which constantly bears against the rope (17) and can be rotated about a rotational axis (A1) parallel to the pivot axis (4). The pivoting frame (3) can be pivoted freely downwards. The limit switch (12) is provided with a third switch position into which it is moved when the pivoting frame (3) pivots downwards, the limit switch (12) in its third switch position releasing the power supply only for the upward direction of rotation of the winch motor.

Description

The invention relates to a safety device for the electric cable winch of a construction hoist, with a substantially rectangular swivel frame arranged immediately below the cable drum surrounded by a protective housing, through which the cable is passed, and which can be swiveled on one side about a swivel axis parallel to the cable drum axis, which is mounted in a console connected to the protective housing, and with an actuator rigidly connected to the swivel frame, which, depending on the position of the swivel frame, acts on a limit switch having at least two switching positions in such a way that in the operating position of the swivel frame the limit switch supplies the current to the winch motor for releases both directions of rotation and only releases the power supply for the downward direction of rotation when the swivel frame is in a raised position with respect to the operating position in a second switching position.

In known construction elevators with such a safety device (brochure from GEDA-Dechentreiter Maschinenbau GmbH, D-8854 Asbach-Bäumenheim "GEDA STAR 150", 9/84), a load weight is attached to the lower end of the freely hanging rope, which depends on carries a load hook at its lower end and a plate at its upper end. This plate is slightly larger than the through opening of the swivel frame. The movement of the swivel frame downwards is limited by a stop, so that the swivel frame assumes an inclined position of approximately 30 ° in relation to the horizontal in its operating position. The through opening of the frame is large enough so that the rope does not normally touch the frame in the operating position. The rope becomes almost complete wound on the cable drum and the load hook moved upwards, then the plate of the load weight abuts on the swivel frame and lifts it. In this case, the limit switch is moved into its second switching position via the actuating element connected to the swivel frame and the power supply for the upward direction of rotation of the winch motor is interrupted. This stops the winch motor. However, the limit switch is designed so that in its second switching position the power supply to the winch motor remains released for a downward direction of rotation. If the drive command for the downward movement of the load hook is given by actuating the down switch button on the control switch, the winch motor can therefore rotate in the downward direction of rotation. This ensures proper winding and unwinding of the rope in the uppermost position of the load hook.

However, winches from construction lifts are often set up and taken down. It can happen that the cable winch is hung so high that the load hook cannot reach the ground and after the cable has been completely unwound it is wound onto the cable drum in the opposite direction. A similar thing can happen if the load hook gets caught somewhere and this is not noticed. Even then, the rope is completely unwound from the rope drum and wound up in the wrong direction. This then leads to the cable cutting into the protective housing surrounding the cable drum, as a result of which not only the protective housing but also the cable are damaged. In addition, the travel commands on the control switch work in the opposite direction. This makes the safety device ineffective. The fully raised load hook lifts the swivel frame and thereby brings the limit switch into its second end position. However, the power supply for the normal downward rotation direction remains in this second end position of the winch motor continues to be released, the normal downward direction of rotation of the winch motor corresponding to an upward movement of the rope if the rope is wound upside down. Since the safety device is no longer working, the load hook can reach the protective housing of the cable drum, which not only damages this, but also the swivel frame. In addition, the winch then stops working at all, because when the swing frame is raised, the limit switch is in its second end position, and in this second end position the power supply to the winch motor, which normally corresponds to an upward direction of rotation, is blocked. If the rope is wound upside down, the up switch button on the control switch would have to be pressed to lower the load hook. However, since the upward direction of rotation of the winch motor is blocked, the winch motor can no longer rotate in a direction of rotation which would correspond to an upward movement of the rope wound upside down. A rope wound upside down also poses a great risk of an accident, since the travel commands given at the control switch by operating the respective control buttons work in the opposite direction.

The same disadvantages also have a known device on a cable winch (GB-A-832 367), which should switch off the winch motor if the cable tension is too high due to overloading or if the cable tension is too low due to slack rope formation. This device is arranged below the rope drum between two rope pulleys. It has a housing which can be pivoted about a horizontal axis and in which a contact roller is rotatably mounted about a horizontal axis. This contact roller is pressed by the dead weight of the housing and the contact roller as well as by spring force, the size of which is adjustable, against the piece of rope running between the two rope rollers with a predetermined force. On a fixed arm, on which the housing is also pivotally mounted, two limit switches are provided which can be actuated by adjustable stops on the housing. If the rope tension is too high or the rope tension is too low, the contact roller moves out of its normal central position and also pivots the housing, so that one of the two limit switches is actuated and the winch motor is thereby stopped. By means of suitable hand-operated means, the design of which is not specified, the device is to be made operational again after the rope tension is too high or too low. Since in this device the rope piece leading to the rope drum is guided over a rope pulley, the contact roller does not react when the rope is completely unwound under load and wound upside down on the rope drum. In addition, the cable pulley provided between the device and the cable drum prevents transverse movement of the cable when it is being wound up on the cable drum and thus prevents it from being wound up in an orderly manner.

A device for preventing slack rope in load winds is also known (DE-B -1 170 126), in which a swivel frame which can be freely pivoted downward is provided above a rope drum. This swivel frame has two axially parallel rollers, between which the rope is passed. A torque is exerted on the swivel frame by a weight and an additional leg spring, so that the swivel frame is pivoted away from the rope drum when slack rope occurs. A switch cam is connected to the swivel frame and actuates a limit switch having two switch positions. When swiveling the swivel frame out of the operating position, the winch motor is first switched off by opening a first contact in the limit switch and when swiveling the swivel frame further by closing a second contact switched in the opposite direction. However, this known safety device for an electric cable winch cannot prevent the cable from being wound up on the cable drum in the opposite direction.

The invention is therefore based on the object of providing a safety device for the electric cable winch of a construction hoist of the type mentioned at the outset which, with a simple construction, prevents the cable from being wound up on the cable drum in the wrong direction.

This is achieved according to the invention in that the swivel frame on its side facing away from the swivel axis has a roller constantly in contact with the rope, which can be rotated about an axis of rotation parallel to the swivel axis, in that the swivel frame can be swiveled freely down to a position at the maximum which the roller rests against the rope which is completely unwound from the rope drum and is wound up winding on the rope drum and hangs down from the rope drum, and that the limit switch has a third switch position, in which the limit switch when the pivot position is pivoted freely downward with respect to the operating position is brought by the actuator, whereby the power supply is released only for the upward direction of rotation of the winch motor.

With the new safety device, the roller is in constant contact with the tensioned rope during normal operation. As a result, the swivel frame is held in its operating position. However, if the load hook gets stuck somewhere, the rope will become slack. As a result, the roller loses its support on the rope and the swivel frame pivots under its own weight, possibly supported by spring force. The actuator connected to the swivel frame brings the limit switch into its third switch position, in which the further power supply, which causes the winch motor to rotate downward, is interrupted. The winch motor is stopped and the rope cannot unwind to the extent that it would be wound onto the rope drum in the wrong direction. Even if you press the down button again, the winch motor will no longer turn in the downward direction. However, since the power supply for the upward direction of rotation of the winch motor remains enabled in the third switch position of the limit switch, it rotates in the upward direction of rotation when the upward switch button is actuated, and the rope is properly rewound. The same happens if the load hook cannot reach the floor and the rope is completely unwound from the rope drum. In this case, the rope remains under tension. However, when the rope has been completely unwound from the rope drum, the attachment point of the rope moves to the rope drum upon further rotation of the cable drum from one point of a horizontal diameter to the diametrically opposite point. The tensioned rope is hereby offset by the diameter of the rope drum in the direction of the swivel axis of the swivel frame. The roller, which is still attached to the rope, follows this displacement of the rope and the swivel frame swivels downwards. The limit switch thus reaches its third switching position and the power supply in the downward direction of rotation of the winch motor is interrupted, as described above. In any case, the winding of the rope in the wrong direction of rotation and the associated disadvantages are definitely avoided.

Advantageous refinements of the inventions are characterized in the subclaims.

Figur 1

eine Seitenansicht der Elektroseilwinde eines Bauaufzuges mit Sicherheitsvorrichtung in Betriebsstellung,

Figur 2

eine Seitenansicht der Elektroseilwinde mit dem Lasthaken in oberster Stellung,

Figur 3

eine Seitenansicht der Elektroseilwinde in einer Störstellung,

Figur 4

einen Schnitt nach der Linie IV-IV der Figur 1.

The invention is explained in more detail below with reference to an embodiment shown in the drawing. Show it:

Figure 1

a side view of the electric cable winch of a construction elevator with safety device in the operating position,

Figure 2

a side view of the electric cable winch with the load hook in the uppermost position,

Figure 3

a side view of the electric cable winch in a fault position,

Figure 4

a section along the line IV-IV of Figure 1.

The cable drum 1 of the electric cable winch of a construction hoist is surrounded by a protective housing 2. It is driven by a winch motor, not shown. An essentially rectangular swivel frame 3 is pivotably mounted below the cable drum 1. For this purpose points the swivel frame has on one side a swivel axis 4 which is rotatably mounted in a bracket 5 connected to the protective housing 2. The pivot axis 4 extends parallel to the cable drum axis A.

On its side facing away from the pivot axis 4, the pivot frame 3 has a roller 6 which can be rotated about the axis A1. The axis A1 is arranged parallel to the pivot axis 4 or parallel to the cable drum axis A. The swivel frame 3 can be freely pivoted downwards. The swiveling downward movement can optionally be supported by a torsion spring in the form of a leg spring 7 or the like. The dead weight of the swivel frame 3 and the leg spring 7 exert a torque M acting clockwise according to FIGS. 1-3.

With the swivel frame 3, an actuator 9 is firmly connected in the form of a disc via the screw 8. The actuating member 9 or the disk has a cutout 10 with two boundary surfaces 10a, 10b running in the radial direction. The switch lever 11 of a direction-sensitive limit switch 12 engages in the cutout 10. The shift lever 11 can assume the three different shift positions shown in FIGS. 1-3.

At the free, lower end of the rope, the load weight 13 is arranged, which carries the load hook 14 on its underside and a plate 15 on its top. The diameter of this plate 15 is so large that the load weight 13 can under no circumstances pass through the passage opening 16 of the swivel frame or jam in the passage opening 16. The limit switch 12 is connected to the protective housing 2 or the housing of the winch motor.

Normally, the rope 17 hangs vertically downwards, tensioned by the load weight 13 or by the load. The roller 6 lies against the tensioned cable 17 and thus holds the swivel frame 3 in its operating position shown in FIG. 1. In this position, the switching lever 11 of the limit switch 12 is in its first switching position (middle position). In this first switch position, the limit switch supplies power to the winch motor for both directions of rotation, i.e. for the upward and downward direction of rotation, free. The upward direction of rotation means the direction of rotation of the winch motor in which it drives the cable drum 1 in the direction B counterclockwise, so that the cable 17 is wound on the cable drum 1 and thus the load hook 14 is moved upward. The reverse direction of rotation of the winch motor, in which the rope is unwound from the rope drum 1 and the load hook 14 is moved downward, is referred to as the downward direction of rotation. In the first switching position of the shift lever 11, lifting and lowering movements of the load hook 14 are possible.

If the load weight 13 comes close to the cable drum 1 and the winch motor is not switched off via the control switch (not shown), then the plate 15 comes into contact with the roller 6 and thus lifts the swivel frame from its operating position shown in FIG. 1 to its position shown in FIG 2 switch-off position shown. The shift lever 11 is brought into its second shift position shown in FIG. 2 by the radial boundary surface 10a of the actuating member 9. In this second switch position, the power supply to the winch motor is interrupted for the upward movement. The winch motor is switched off and the cable drum 1 is stopped. However, since the power supply in the second switch position is still released for the downward direction of rotation, the winch motor can be driven in the downward direction of rotation when the downward switch button on the control switch is actuated, and the load hook 14 can thus be lowered from its uppermost position. Swing frame 3 and shift lever 11 then return to the operating position shown in Figure 1.

If the load or the load hook has now reached the ground and the winch motor is not switched off via the control switch, then the rope 17 becomes slack according to FIG. 3. As a result, the roller 6 loses its support and the swivel frame 3 swivels under its own weight and under the action of the torsion spring 7 down into the position shown in FIG. 3. Here, the switching lever 11 is pivoted into its third switching position by the boundary surface 10b of the actuator 9. In this third switch position, the power supply for the downward rotation of the winch motor is interrupted and the cable drum 1 is thus automatically stopped. In the third switch position, however, the power supply remains released for the upward movement, so that after the upward switch button on the control switch is actuated, the winch motor drives the cable drum in direction B again, whereby the cable 17 is wound on the cable drum 1.

As long as the rope 17 is properly wound onto the rope drum 1, it runs tangentially onto the rope drum 1 on the right-hand side according to FIGS. 1-3. If the rope 17 is accidentally completely unwound from the rope drum 1, the fastening point P of the upper rope end on the rope drum 1 moves during a half turn of the rope drum from the right side to the left side of the rope drum, as shown in broken lines in FIG. Although the rope in this Position can still be tensioned by the load or the load weight, namely when the load or the load weight 13 has not reached the floor, the swivel arm 3 can move by the movement of the attachment point P from right to left and the associated displacement of the tensioned rope 17th swivel from right to left, downwards. As a result, the shift lever 11 is also brought into its third switching position and the winch motor is thus automatically switched off.

So that the direction-sensitive limit switch 12 can control the current supply to the winch motor in its three switching positions in the manner described above, it has separate switching inserts for switching the upward or downward rotation.

Claims (3)

1. The invention relates to a safety device for the electric winch of a building site lift, with a substantially rectangular swing frame (3) disposed directly underneath the cable drum (1) which is surrounded by a protective casing (2); said swing frame having the cable (17) passing through it, and being pivotable at one side around a pivotal axis (4) parallel to the axis (A) of the cable drum, said axis (4) being mounted in a bracket (5) connected to the protective casing (2) and with, rigidly connected to the swing frame (3), an actuating member (9) which acts upon an end-switch (12) having at least two switch positions, in dependence on the position of the swing frame (3), in such a way that, in the operative position of the swing frame (3), the end-switch (12) allows the power supply to the winch motor for both directions of rotation, and in which, with respect to the operative raised position of the swing frame (Fig. 2), it provides power supply only for the downward direction of rotation, characterised in that the swing frame (3) has on its side remote from the pivotal axis (4) a roller (6) permanently bearing on the cable (17), and which is rotatable around a rotary axis (A1) parallel with the pivotal axis (4), that the swing frame (3) is freely pivotal downwards into a maximum position (according to Fig. 3) in which the roller (6) bears on the cable (17) which has been totally unwound from the drum (1), is hanging downwards under tension from the drum, and is being wound on to the drum again in the wrong direction, and that the end-switch (12) has a third switch position into which said end-switch is brought by the actuating member (9) when the swing frame is in a freely downwardly pivoted position (according to Fig. 3), with respect to the operative position, so that the power supply is released only for the upward rotary direction of the winch motor.
2. A device according to Claim 1, characterised in that the swing frame (3) is loaded by a spring (7) which exerts a downwardly-directed force on the swing frame.
3. A device according to Claims 1 and 2, characterised in that a torsion spring (leg spring) (7) is located between the swing frame (3) and a bearing block (5) supporting the pivotal axis (4).

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