Patent Application
20140217340
This application claims the priority of Patent Application Serial No. DE 10 2013 201 860.6 filed on Feb. 5, 2013, pursuant to 35 U.S.C. 119 (a)-(d), the content of which is incorporated herein as if fully set forth herein.
The invention relates to a method for influencing a cable winch force acting on a cable drive and a device for carrying out a method of this type.
Devices for winding a cable onto a winch of a cable drive are known from DE 10 2004 046 130 A1, from FR 2 843 954 A1, DE 24 51 547 A1, DE 23 01 623 A1, DE 38 19 447 C2, DE 10 2007 031 227 A1, U.S. Pat. No. 4,172,529 and from U.S. Pat. No. 4,204,664.
An object of the present invention is to improve a method for influencing a cable winch force acting on a cable drive in such a way that the cable winch force acting on the cable drive can be controlled depending on a respective cable drive operating state and an outer cable force.
This object is achieved by a method for influencing a cable winch force acting on a cable drive, comprising the method steps of providing a cable drive with a drivable winch and with a cable that can be wound on the winch, providing a device for producing a traction sheave cable force on the cable, determining an outer cable force, predetermining a cable drive operating state, providing a control-regulating unit to influence the traction sheave cable force, producing a control-regulating variable by means of the control-regulating unit depending on the outer cable force and the predetermined cable drive operating state, producing the traction sheave cable force by means of the device and influencing the traction sheave cable force by means of the control-regulating unit in such a way that the cable winch force acting on the cable drive can be controlled depending on the respective cable drive operating state and the outer cable force, wherein the device is a traction sheave drive, wherein a four-quadrant operation of the traction sheave drive is reproduced by means of the control-regulating unit, and wherein the four traction sheave drive operating states are no-load lifting, no-load lowering, load lifting and load lowering.
It was recognised according to the invention that a cable winch force can be controlled depending on a respective cable drive operating state and on an outer cable force by exerting a traction sheave cable force on a cable of a cable drive. By combining the cable drive, which basically allows only two operating states, with a device for producing a traction sheave cable force, which is, in particular, configured as a traction sheave drive, four different operating states can be reproduced. As a result, it is possible to influence a cable winch force acting on the cable drive, which can be determined, in particular, by means of a cable force measuring unit, in such a way that the cable winch force can be controlled depending on a cable drive operating state and on an outer cable force. Controlled and low-wear winding is made possible in that the cable is wound on at a cable winch force which is as constant and, in particular, low as possible. An additional drive of the cable in front of the winch can make this possible. This drive principle is based on the cable friction according to the Euler-Eytelwein formula. An acceptable tolerance range of the cable winch force, which is, in particular, +/−20% of a predetermined desired cable winch force, is taken to mean a constant cable winch force. In particular, the acceptable cable winch force range comprises +/−10% of the predetermined desired cable winch force and, in particular, +/−5% of the predetermined desired cable winch force. For example, a value of 2% of a minimum breaking force of the cable or of 10% of the nominal force of the cable drive is used as the desired cable winch force, which is used to prestress the cable for optimal winding or unwinding of the cable. By means of a cable, the device can be connected at a first cable end to the cable drive and at a second cable end to a load receiving device, such as, for example, a load hook, in particular a hook block. The cable in particular, in each case, loops the two traction sheaves. The cable drive operating state is fixed by an actuating direction of the cable drive, for example by a rotational direction of a winch of the cable drive, in other words a winding or unwinding of the cable. An outer cable force is caused, in particular by a load received by the load receiving device. Various traction sheave drive operating states can be determined depending on the respective cable drive operating state and depending on the outer cable force for a provided device for producing a traction sheave cable force on the cable. Four traction sheave drive operating states are produced, in other words with or without a load suspended on the load receiving device and the winding or unwinding of the cable from the winch of the cable drive. These traction sheave drive operating states are designated no-load lifting, i.e. winding the cable without a load, no-load lowering, i.e. unwinding the cable without a load, load lifting, i.e. winding the cable with a load and load lowering, i.e. unwinding the cable with a load. In particular, it is therefore possible using the method according to the invention to both wind and unwind the cable in a controlled manner, in other words at a constant cable winch force, it being unimportant whether the cable drive is loaded by an outer load, i.e. whether a load is suspended on the load receiving device or not. Wear to the cable, in particular on a winch wound in several layers, is reduced. Since, a monitoring and adaptation of the cable winch force is made possible in particular also when winding the cable onto the winch of the cable drive, winding errors and/or a cable fault as a result of a too loose, unstable cable assembly can be avoided. In particular, it can be avoided that a cable wound on incorrectly in this manner, which is then subject to a strong outer cable force as a result of a high outer load, is drawn in or forced in from an upper layer of a cable winding into deeper layers located therebelow with a looser winding. This form of cable damage is ruled out by the method according to the invention. Additional cable-braking devices, which are called cable baiters, can be dispensed with in the method according to the invention.
In particular, a four-quadrant operation of the traction sheave drive can be reproduced by means of a control-regulating unit.
Additional operating states are made possible thereby, which are not depicted by means of a two-quadrant operation known from DE 10 2004 046 130 A1 for producing a constant load when winding a cable onto the cable drive. In particular, the method according to the invention allows additional operating states to be depicted. The depiction of the additional operating states takes place by means of an adjustment of the operating states in an incremental control range. This means that the control of the cable force acting on the cable drive is also possible for the additional operating states of load lowering and no-load lowering. The cable guidance and the cable stress are thereby improved. In particular, the situation is ruled out of a so-called hanging cable or slack cable being produced as a result of low stressing of the cable, as, because of the outer cable force, the cable is not stressed by adequate tensile loading. An inadequate tensile loading may be present when, for example, the loading of the cable is only provided by a suspended hook or a reeved load block, and, in particular, an outer load is absent. Furthermore, it can be ruled out that a tearing of the cable will occur as a result of over-stressing. In particular, a method of this type can be advantageously used for mutual control of multiple cable reeving in double cable operation. In multiple cable reeving, the cables can be decelerated very differently because of cable braking forces caused by the sheaves. In this case, a compensation of the cable forces takes place in such a way that a tilting, in other words, a twisting of a double load block is avoided with, in particular, additional devices, which are known from EP 1 924 520 B1 and/or from EP 1 773 706 B1 for avoiding the tilting of a double load block, not being required. These cable force differences can already be dynamically taken into account and avoided, in particular compensated, in the cable run during four-quadrant operation. It is conceivable that a method in the four-quadrant operation mentioned of the traction sheave drive will for the first time allow a double cable drive with extremely long cable lengths of, for example, more than 1000 m.
It is advantageous if the traction sheave drive has a drive motor, in particular an electric motor, which, depending on the cable drive operating state, provides a torque of a required size, so that a traction sheave cable force caused by the cable sheave drive leads to a desired cable winch force. In particular, a control algorithm of the traction sheave drive depends directly on the cable drive operating state.
A method according to which the cable winch force acting on the cable drive can be controlled in such a way that it is reduced or increased relative to the outer cable force allows an advantageous control of the cable winch force in relation to the outer cable force.
A method according to which the cable winch force acting on the cable drive can be controlled in such a way that the traction sheave cable force follows a predetermined characteristic curve depending on the outer cable force allows a rapid and effective control of the cable winch force.
A method according to which the outer cable force is determined indirectly from the load force allows a rapid and uncomplicated determination of the outer cable force.
A method according to which the outer cable force is determined directly by means of a cable force measuring device allows a particularly precise determination of the outer cable force.
A method according to which the traction sheave cable force is determined that can be transmitted by means of the device from the outer cable force allows the traction sheave cable force to be monitored.
A method according to which the rotational direction of the winch, which is predetermined, in particular, by an operator, is considered to produce the control-regulating variable allows improved control of the cable winch force.
A method according to which a plurality of input variables, in particular the outer cable force, the load force, the rotational direction and/or the rotational speed of the winch, is used to produce the control-regulating variable allows various influencing variables for producing the control-regulating variable to be taken into account.
A method according to which the traction sheave cable force is controlled in such a way that the resulting cable winch force is independent of the rotational speed of the winch allows a control of the traction sheave cable force in such a way that the resulting cable winch force is independent of the rotational speed of the winch. The traction sheave cable force reacts directly to a change in the outer cable force due to the pressure level in the closed control circuit. The method is independent of the speed of the cable and, in particular, of accelerations or decelerations of the cable.
A further object of the present invention is to improve a device for influencing a cable winch force acting on a cable drive, in order, in particular, to reduce cable wear and to avoid winding errors when winding the cable.
This object is achieved by a device for carrying out a method according to any one of the preceding claims, wherein the device comprises two traction sheaves that can be looped by a cable and at least one drive to drive at least one of the traction sheaves, wherein a traction sheave cable force is produced on the cable by means of the traction sheaves and is influenced by means of a control-regulating unit in such a way that the cable winch force acting on the cable drive can be controlled depending on a respective cable drive operating state and an outer cable force.
According to the invention, it was recognised that two traction sheaves are used to exert a traction sheave cable force on a cable of a cable drive, the traction sheaves being drivable independently of one another at least by means of one drive and, in particular, by means of a drive in each case. The device ensures that the cable force acting on the cable drive is monitored independently of the respective operating type of the cable drive. The traction sheave drive can thus be controlled independently of the cable drive. It is thus possible by means of the two traction sheaves to assist the winding and unwinding of the cable from the winch of the cable drive in a targeted manner, i.e. to load the winch of the cable drive or to relieve it. Because of the assisting effect of the traction sheave cable force, the winch of a primary cable drive can be designed to be smaller and, in particular, with a reduced power and brake. As a result, the total weight of the winch arrangement of a work machine can be reduced and the cost outlay reduced. It is also possible to retrofit said device on an already existing work machine. When the device is configured as a refitting kit for an existing work machine, it is, in particular, unnecessary to place increased safety demands on the traction sheaves, as functions relevant to safety such as, for example, a braking function have to be satisfied in any case on the cable drive present on the work machine. In particular, the same safety demands are made of the device as a retrofitting kit as of a primary cable drive. Even a temporary failure of the device, for example the traction sheaves icing over can be tolerated. The device, as a retrofitting kit, can be implemented in an uncomplicated manner, in particular with reduced functions, and economically. It is possible to provided pre-equipped brackets and/or hydraulic lines on an intermediate piece in order to simplify later retrofitting of the device according to the invention. It is advantageous to provide, in the geometric vicinity of a traction sheave drive, a self-sufficient hydraulic unit, which is known, for example, from EP 1 641 703 B1 and to already set up the necessary cables for this beforehand.
A device in which the control-regulating unit has a signal connection to the at least one drive to control or regulate the drive torque and/or drive rotational speed of the drive allows an automatic adaptation and control of the traction sheave cable force by controlling the drive torque and/or drive rotational speed of at least one of the drives.
A device in which the at least one drive is a hydraulic motor, an electric motor or a motor-gearing combination allows a simplified and direct activation of the drives. In particular, it is advantageous for a predetermined desired torque to be able to be directly produced and activated. A device with hydraulic drives for the traction sheaves can be can be realised in an uncomplicated and economical manner. In particular, it is possible to provide a supply of the hydraulic drives by means of a hydraulic mechanism which is present in any case on a work apparatus. It is also possible for the hydraulic drives to be activated by a closed, self-sufficient hydraulic circuit. The use, in particular, of frequency-controlled electric motors allows a direct and more precise control of the drive torque. The electric motors can also be more easily integrated into a possible control loop. A control geared at this can take place close to real time. Moreover, electric motors have improved efficiency compared to hydraulic drives. The environmental pollution is reduced due to reduced emissions. The drive can also be configured as a motor-gearing combination. A combination of this type allows a particularly compact implementation of the drive. The drive can thereby be arranged, in particular, advantageously on the device and, overall, allows a compact, weight-reduced configuration of the traction sheave drive.
A device in which the at least one drive has an automatic torque control allows a simplified and effective control of the traction sheaves.
A device in which each traction sheave has a plurality of grooves for cable guidance allows a targeted and, in particular, robust cable guidance on the traction sheaves. In particular an overlaying of individual cable strands in the device is avoided. A device in which the traction sheaves in each case have a different number of grooves and, in particular, one traction sheave has precisely one groove more than the respective other traction sheave, allows an advantageous cable guidance.
A device in which the traction sheaves are arranged in a receiving frame allows an uncomplicated and simultaneously stable arrangement of the device on a work machine, in particular a crane.
An embodiment of the invention will be described in more detail below with the aid of the drawings.
The use of the device 2, which is configured as a traction sheave drive, can be applied to various work machines, in particular a crawler crane.
The device 2 will be described in more detail below with the aid of
A bearing journal 14, which is rotatably mounted in a floating bearing 15, which is arranged in a bearing opening 16 of the first traction sheave 4, is provided on a bearing vertical wall 13 arranged opposite the drive vertical wall 10. The first drive 7, the first gearing 8, the bearing journal 14 and the floating bearing 15 are oriented concentrically with respect to one another along the rotational axis 6.
The first traction sheave 4, at its outer cylinder casing face, has four grooves 17, which are used to guide the cable during the winding and unwinding of a cable from the first traction sheave 4. The grooves 17 are in each case separated by groove rims arranged in between. Furthermore, the first traction sheave 4 has flanks 18 directed obliquely outwardly from the grooves 17.
The second traction sheave 5 is held in an identical manner on the receiving frame 3. The second traction sheave 5 can be driven about its rotational axis 19 by means of a second drive 20 by means of a second gearing 21. The only difference is that the second traction sheave 5 has three instead of four grooves 17. As a result, a guidance of a cable 22 shown by a dash-dot line in
The device 2 furthermore has a control unit, not shown in
The mode of functioning of the device 2, in other words a method for influencing a cable winch force acting on a cable drive, will be described in more detail below with the aid of
The device 2 is connected at a first cable end of the cable 22, shown on the left in
The outer cable force 33 acting on the cable drive 29 is determined by means of a cable force measuring device, not shown, which may be configured, in particular, as a load torque limiter that is present in any case on a crane. The outer cable force 33 provides the prestressing, with which the cable 22 is wound onto the winch 28. The cable force 33 determined can, in particular, be used as an input signal for the control unit 34 of the device 2. As an alternative to the cable force measuring device, which allows a direct determination of the outer cable force 33, it is also possible to indirectly determine the outer cable force 33 from the load force 31. The indirect determination of the outer cable force 33 is possible in an uncomplicated manner. In particular, the apparatus outlay for this is small.
The cable 22 is wound using a cable winch force 35 onto the winch 28. In order to ensure that in the operating state no-load lifting, the cable 22 is wound with adequate prestressing, in other words not too loosely, onto the winch 28, the traction sheaves 4, 5 of the device 2 are activated and, in particular controlled, in such a way that a traction sheave cable force 36 on the cable 22 counteracts the cable winch force 35. The cable winch force 35 is controlled by the traction sheave cable force 36. The cable winch force 35 is the resultant of the traction sheave cable force 36 and outer cable force 33. The outer cable force 33 is produced from the load force 31 depending on the loading condition from the system, comprising the cable 22, the load block, or a simple load receiving device. The outer cable force 33 counteracts the cable winch force 35. This means that the outer cable force 33 and the cable winch force 35 compensate one another. The outer cable force 33 and the cable winch force 35 are the same in terms of amount, in particular during conventional operation of the device, and mutually cancel one another. A resulting force formed from these two forces 33, 35 is 0. In order to be able to change the cable winch force 35 with a predetermined outer cable force 33, in particular to increase or reduce it, the traction sheave drive 2 is inserted. Depending on the load condition and operating type, the cable winch force 35 can be increased or reduced by the traction sheave cable force 36. In particular, the direction of action of the traction sheave cable force 36 can be adjusted by the drive direction of the traction sheaves 4, 5. The traction sheave cable force 36 can thus be adjusted to be in the same or opposite direction to the cable winch force 35.
The interrelation of the cable forces 33, 35 and 36 is graphically shown in the characteristic curve graph according to
In order to ensure the traction sheave cable force 36 according to
The traction sheave drive operating state load lifting according to
The traction sheave drive operating state load lowering according to
The traction sheave drive operating state no-load lowering shown in
The mode of functioning of the hydraulic control will be described in more detail below with the aid of
| Number | Date | Country | Kind |
|---|---|---|---|
| 102013201860.6 | Feb 2013 | DE | national |
