DE2910057A1 - Jib crane overload protection system - has programmable computer with comparator for actual and max. permissible values - Google Patents

Abstract

The overload protection system is for a crane with a variable-length derricking jib, and it has measuring devices for actual-load values. A digital computer with storage unit is programmed with maximum values at separate points over the operating range and it calculates values at intermediate points by interpolation. A comparator for the actual and maximum permissible values emits an overload signal where they are equal. The storage unit has a number of vertical storage planes, occupied by stored data in a set sequence and also supplying this in a set sequence. It is only in the lowest plane that load or tipping moment limt values are stored relating to a sutable operating value. In the higher ones for other operating values addresses or coefficients are stored, allowing selection of values stored in the next lower plane.

Description

Load moment limiter for a crane

The invention relates to a load torque limiter for a crane one that can be swiveled around a horizontal axis and, if necessary, around a vertical axis and is adjustable in length Boom, measuring transducers to record the for the momentary load condition of the Crane's characteristic actual operating parameters, a digital computer with memory, in which force or torque limit values are assigned to discrete points of a multidimensional Operational variable field are preprogrammed, the computer by interpolation Intermediate values of the force or torque limit values for measured actual operating parameters determined and a comparator, which the respective limit value with the measured The actual value of the force or the moment is compared and, if they are equal, an overload signal triggers.

A load torque limiter of this type is known (DE-OS 26 41 082), the memory of which is a core memory and is connected to programming devices target. The publication does not have anything to do with the structure and creation of this memory remove.

The structure of an accumulator for a load torque limiter for cranes the aforementioned Arbzw. a way of storing and discovering Limit values with retrieval of stored values is also known (lecture manuscript of Friedrich Krupp GmbH, Krupp Research Institute "Use of microprocessors in the Load moment limitation of mobile cranes ", RE 111.7.3), with load values of given Load curves stored at discrete support points of a program memory are. The number of discrete support points and their distances are in one Grid field for each load-bearing mast curve to be saved is rigidly specified. For investigation of limit values for the position of the boom that lie between the support points, is interpolated according to a hyperbolic function.

The invention is based on the object of the memory and its creation and thus the ability to program the load torque limiter while saving More flexible storage spaces, while at the same time increasing the accuracy of the iachbilduiiy the limit value curves specified by the crane manufacturer are to be improved.

To solve this problem, in the case of a load torque limiter, the above mentioned type provided according to the invention that the memory several vertically Arranged storage levels with a specific order of precedence for the individual storage levels when allocating memory locations and when calling up stored values, whereby only in the storage level lowest rank limit values in assignment to a suitable operating variable are stored and in the other memory levels higher rank assigned to other company variables, addresses or codes are stored, which are a selection of the next lower memory level enable stored values.

In the case of the invention, there is an individual consumption of memory spaces possible depending on the course and length of the limit value curve to be stored. Be like that for storing limit value curves of short length or limit value curves to a large extent straight course only a few memory slots occupied. On the other hand, you can be strong with yourself changing curve shape of the limit value curve - or in the case of long limit value curves . many bases can be chosen. This is possible with a very large number of operating modes or setup states of the crane save a large number of storage spaces.

Another important advantage of the invention is that in the According to the invention, memory does not have a rigid grid with always constant intervals of the individual bases is more realized. The distances between the support points in the Grids can be varied depending on the course of the limit value curve to be simulated. This improves the quality of the simulation of the limit value curves.

According to one embodiment of the invention it is provided that the memory a first memory level for storing code numbers and addresses in association for different setup states, a second memory level for storing code numbers and addresses associated with discrete cantilever length values and a third level of memory for storing limit values in association with discrete values of projections and / or Swivel angles of the boom comprises, and that the first memory level the first place, the second memory level the second place and the third memory level den take third place in the ranking.

Because of the variability of the number and the distance between the support points in the grid field of the memory is sufficient according to a further development of the invention, when the computer is between the limit moments found in the third memory level to determine the limit torque associated with the measured actual operating state of the crane linearly interpolated two-dimensionally, e.g. between two over adjacent ones Limit torque values stored at a constant radius and between two limit torques stored via adjacent extension values constant boom length.

According to one embodiment of the invention, it can also be provided that in the third storage level limit moments for the unloaded cantilever and are stored for the loaded boom, and that the computer is used to determine of the limit torque caused solely by the load on the crane hook Limit torque cantilever values from the limit torque total values s; subtracted. This embodiment is advantageous, in particular, when the actual load state is recorded by measuring the total torque, for example by measuring the pressure in the luffing cylinder of the boom.

The invention is shown below with reference to schematic drawings further details explained in more detail. They show: FIG. 1 a diagram of a mobile Telescopic crane with important occurrences.

Company sizes; 2 shows a block diagram of the structure of a load torque limiter according to the invention; 3 shows a schematic representation of the structure of a memory the load torque limiter according to Fig..l; 4 shows a three-dimensional diagram to illustrate the Interpolation to be carried out in the load torque limiter to determine limit torques.

Fig. 1 shows schematically the boom of a mobile telescopic crane telescopically extendable main boom 1 is by means of a luffing cylinder 2, the has a fixed base point Z on a superstructure (not shown) of the crane, in its angular position relative to the vertical can be changed (angle o ().

At the upper end of the main boom 1 carries a stem 3 on which a Jib boom 4 is pivotably articulated (angle). The fly jib 4 carries in turn, a stem 5 on the jib head, on which a load Q hangs Load can be lifted with a hoist rope 6, which is carried by a rope drum via pulleys 8, 9 7 is led to the load Q.

The important operating parameters shown in FIG. 1 are taken from the following list: LHA = length of the main boom 1 LSPA = length of the fly jib 4 HBZ = Lever arm of the luffing cylinder2 L1 = Length of the stem 3 for the jib linkage L2 = difference between the nominal length of the tip and the actual length L3 = length of the stem 5 of the jib head D = distance between the crane support and the center of the slewing ring = = Angle of the main boom to the vertical = = angle of the tip relative to the angle o (R = radius (outreach) AR = radius enlargement due to the cantilever deflection HHub = distance of the hoist rope from the pivot point of the boom SE = number of rope shears Q = load hanging on the crane hook Mges = total actual moment acting on the crane Mleer = moment of the unloaded boom acting on the crane the following (and also in Fig. 3) referred to as "radius" is that lever arm around which the crane can tip over if it is overloaded. This radius is not from the center of the slewing ring but taken at a distance D from it, from the center of the slewing ring up to the crane support selected in each case.

This radius R can be calculated from the operating parameters according to the following equation determine: R = LHA. sense + L1. sin (o "+ 900) + (LSPA '+ L2) sin (ty + L3.sin (« ++ 9Oc) - 0 With the help of this equation, the total torque is Mges - Mleer + Q (R + D) - Q HHub / SE A block diagram for a load torque limiter is based on the Fig. 2 describe.

Measuring transducer for the actual operating parameters, namely a measuring transducer 10 for the angle ffi of the jib boom 4, a combined measuring transducer 12 for the length LHA and the angle α of the main boom and a measuring transducer 14 for the operating mode with which the support area via the crane electrical system 15 is detected, and finally a measuring transducer 16 in the form of a pressure transducer, the the pressures on both sides of the piston 18 of the rocker cylinder 2 measures, lead their measured values to a preamplifier 20. The combined transducer 12 for the Sizes of the main boom 1 are lift end values from a lift limit switch 11 for the Main boom and entered from a hoist limit switch 13 of the fly jib 4, as soon as these limit values are reached.

Via a schematically indicated connection 22 with 48 lines and an analog-to-digital converter 24 is the output of the preamplifier 20 with a digital Central unit connected, the a computer 28 and a memory arranged thereon 30 includes.

The central unit 26 is connected to a multiplexer circuit 32 Display device 34 connected. Furthermore, the central unit 26 is directly connected to a Disconnection device 36 connected, which all movements increasing the load torque, especially the load stroke, switches off when the load torque reaches a critical value exceeds.

The load torque limiter described works on the principle of Setpoint / actual value comparison, the setpoint value being a limit value namely that for the current one Operating state is the permissible limit torque.

This limit torque is stored in memory 30 by computer 28 Limiting torques determined while the actual torque is measured after measuring the force in the tilting cylinder 2 and after determining the radius R according to the equation given above by functional Linking these quantities is formed.

The memory 30 is constructed so that it is particularly economical Use of the memory locations a good replica of the one specified by the crane manufacturer Limit torque curves for all operating states enabled. The structure of the memory is explained in more detail below with reference to FIG.

According to FIG. 3, the memory 30 has three memory levels, namely one first memory level 40 for storing the operating modes, a second memory level 42 for storing the so-called length table and a third memory level 44- to save a radius / angle table. The storage via radius and Lengths are necessary because these sizes are due to the changeability of the length LHA of the Main boom 1 (telescope) are geometrically independent variable sizes.

The three storage levels are arranged "vertically", with the order of precedence of the storage levels begins with the storage level 40 as the highest level and ends with the storage level 44. as the lowest storage level of the lowest rank.

The shutdown curves are stored sequentially in the levels.

Operating modes (short: BA) are stored in the first memory level 40, with a code number for each operating mode, the length of the fly jib, the The tip angle and an address are stored in the second memory level 42.

In the second memory level 42 there are different modes for each operating mode Telescope step lengths stored, with code numbers and a Address stored in the radius table of the third memory level 44 is. The levels between each length can range from four to a maximum of thirty-two Steps are expanded. There are also multipliers in the first two memory levels voon 1 to 8 for the length, the radius and the nominal value with which the stored limit torque values can be "stretched".

The third memory level contains for each operating mode and each length level for a number of radii a "setpoint" for the limit load torque, a '9 empty torque value " for the moment generated by the unloaded boom and a lever arm'HHub of the hoist rope saved at the corresponding radius.

For example, if there are five operating modes in memory level 40, a the second memory level 42 eight length increments and in the third memory level eight radius steps are saved, then a total of 320 "support points" needed. The memory can of course also have more memory spaces as required exhibit.

The structure of the memory according to FIG. 3 with the sequential described As already mentioned, table technology allows dynamic storage, i.e. depending on the requirements a variation of the length steps and the Ra, die steps both in terms of their Number as well as in terms of their distance. That makes how useful this is Diagram according to FIG. 4 clearly. In Fig. 4 are above a plane with / ZW8 perpendicular to each other standing axes for the length L and the radius R to the maximum total moment Mmax related cantilever limit torques M empty plotted in%. The to the individual Curves resulting in length increments are denoted by the reference symbols 46, 48, 50, 52. Due to the memory structure described, it is now possible, depending on the course the surface described by the curves 46 to 52, the distance of the curve fits to choose, i.e. to change the length increments in the direction of the length axis L and likewise the points on the curves, where the length L is constant in each case is, by varying the distance between the steps of the radius depending on the course of the curve . to choose a smaller or larger distance. So the grid is in both directions L, R variable. The area formed by curves 46, 52 represents the cantilever limit torque area. Of this area, however, only the discrete limit moments are known that are caused by the Points on the curves are symbolized. The actual values for each actual existing length L and the respective actually existing radius R are in operation between the bases. Due to the favorable, the curve shape adaptable With the number of support points, it is sufficient if the computer 28 interpolates linearly in two dimensions. To do this, it first interpolates with a fixed value that is adjacent to the operating point smaller radius R1 between the Points L1R1 and L2R1, i.e. between the smaller length L1 and the larger length L2 than the length at the operating point LpRp. Then the computer interpolates while maintaining the larger radius R2 the points L1 R2 and L2 R2 again with a smaller length L1 and a greater length L2. The result of these two interpolations are the limit torques at the intermediate points Lp, i.e. in Fig. 4 the points Lp R1 and LP R2 with a smaller radius R1 and a larger radius R2.

In a third interpolation, the computer 28-now interpolates these two points at point LpRp, i.e. the cantilever limit torque at the operating point.

In the same way, the total limit torques are derived from the stored Total limit torque values determined.

In order to obtain the torque component caused solely by the load, the computer subtracts the idle boom limit torque determined at the respective operating point from the determined total limit torque.

The load torque limiter described is particularly suitable for the execution in microprocessor technology, which with little equipment-technical effort the execution of extensive calculations, easy adaptation to special crane types on-site programmability, self-test and further expandability enabled, just to name a few advantages.

Claims (4)

Claims 1. Load torque limiter for a crane with one-to-one horizontal Axis and, if necessary, boom that can be pivoted about a vertical axis and adjustable in length and sensors for recording the current load condition of the crane characteristic actual operating parameters, a digital computer with memory, in the force or torque limit values assigned to discrete points of a multidimensional Operational variable field are preprogrammable, the computer by interpolation Intermediate values of the force or torque limit values for measured operating parameters are determined, and a comparator that compares the determined limit value with the measured actual value compares the force or the moment acting on the crane and, if they are equal, a Overload signal triggers, as a result of the fact that the memory has several vertically arranged storage levels with a specific ranking of the individual storage levels when allocating memory locations and when calling up stored values, where ntrin the lowest-ranked storage level, force or torque limit values in Assignment to a suitable operating memory size are stored and in the other storage levels of a higher rank assigned to different operating parameters in each case Addresses or code numbers are stored that allow a selection of the in each case next lower memory level. 2. Load torque limiter according to claim 1, characterized in that g e k e n n z e i c h n'e t that the memory has a first memory level for storing code numbers and addresses in assignment to different setup states / operating modes), one i memory level for storing code numbers and addresses in association with discrete boom length values and a third storage level for storing limit values in association with discrete ones Includes values of overhangs (radii) and / or pivot angles of the boom, and that the first memory level the first place, the second memory level the second Place and the third tier of storage take third place in the order of precedence. 3. Load torque limiter according to claim 2, characterized in that g e k e n n z e i c h n e t that the computer between the limit moments found in the third memory level to determine the limit torque associated with the measured actual operating state of the crane two-dimensional linear interpolation. 4. load torque limiter according to claim 2 or 3, characterized g e k e n n z e i c h -n e t that in the third storage level limit moments for the unloaded Empty boom and for the loaded boom are stored, and that the computer to determine the limit torque caused solely by the load on the crane hook the calculated limit torque idle boom values from the calculated limit torque total values h subtracted.