FI115162B - A system for weighing loads on the lifting and handling equipment - Google Patents

Description

115162 System for weighing loads on the hoist and transfer device

The invention relates to a weighing system according to the preamble of claim 1 for determining the weight of a load 5 to be handled by a lifting and moving device. The invention relates to a separate end piece for hanging loads, according to the preamble of claim 17, which can be attached to a lifting and transfer device.

To carry out harvesting, there are known off-road machines 10, such as harvesters (Harvester heads) fitted with processing devices, known as harvester heads, for cutting, felling and sawing the growing tree trunk to desired lengths. Sawn timber trunks are collected by another known off-road machine and its handling equipment, which includes a Grapple Loader (Forwarder), and the trunks are transported in its load space. Also known are combination machines, which combine the functions of a harvester and a loader, whereby the loader grapple has a harvester head which is also suitable for loading. Timber frames are also handled by means of booms and loaders mounted on the vehicle, especially 20 log trucks.

• · · «I i t. · * ·. The machines described above comprise a boom for working • v. Parallel motion and whose outer \ boom part to which the tool is attached can operate telescopically. Hell! The assembly comprises at least two, usually three articulated / attachable boom portions that move in a vertical plane. The boom is secured to the work machine by means of a pivot joint to rotate the boom vertically. In harvesters, the entire boom:, '- i swivel arm can also often be tilted at least 3 ° forward and forward. A suitable tool, such as a harvester head or loader grapple, can be attached to the free end of the boom, usually by means of a rotator. The boom is typically operated by a pressure medium, "·" usually controlled by hydraulic actuators:. ' such as cylinders, and control valves.

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For weighing a load to be lifted by a loader, for example a single tree trunk or bundle, load cells are known, for example based on the principle of roll-out 3911737 of U.S. Patent No. 1,616,122, which are coupled between a boom head and a pivot for measuring vertical force. The force is directly proportional to the load. The weighing device extends the distance between the boom head and the tool, which increases swinging and makes the tool difficult to handle. The place is also prone to bumps and collisions. Damage to the weighing machine may impair the carrying capacity and pose a safety hazard.

In addition, a bearing pin 10 pin sensor is known from GB 2037444. The machine can weigh the bucket load based on the load on the bearing pins. The equipment requires joint changes and is subjected to abrasive forces and considerable load simply due to the weight of the boom itself. Other systems that follow the load on the crane structure are known, for example, the system according to US-15 5557526. The system is designed to monitor local loads, which strongly depend on the position of the crane and where actuator and articulation points are located. In addition, systems for determining the load applied by the load are disclosed in U.S. Patents 4057792 and 5160055. The load varies with the length of the crane ···, even if the load remains the same, so it is also necessary to use • · »·. ···. position sensors to determine position.

It is an object of the present invention to introduce a new type of pound! 25 system for weighing loads and in particular eliminates the above-mentioned problems. The system is suitable for a variety of lifting and handling equipment: ···; structures and is as independent as possible of the crane position or reach.

The weighing system according to the invention is disclosed in claim 1. The tip piece according to the invention is disclosed in claim 17.

The advantage of an advantageous embodiment of the invention is the integrated sensing for weighing. The tip of the invention is suitably shaped for measuring purposes, whereby the structure combines good shielding with the ability to determine the load weight of the structure by the basic 115162 3 method. When the measuring device is a separate unit, it is quick and easy to replace. The tip piece is further constructed to be suitable for a separate unit.

5 The tip piece can be attached to a variety of lifting and moving devices and, in addition, the positioning of the sensor enables the position of the boom or the support points of its support structures to be minimized. This avoids position sensors and makes calculation easier. The system is particularly suitable for weighing timber trunks handled by a loader, whereby the total amount loaded or unloaded can be continuously monitored without interruption. The gauge is interchangeable without removing the boom member, tool or swivel.

The invention will now be described in more detail by way of example of some preferred embodiments, with reference to the accompanying drawings, in which: Figure 1 is a side view of a telescopically operating boom in which the kek-20 invention is applied. Fig. 2 shows the free end of the boom of Fig. 1 and a position of the weighing device, seen from the side, Fig. 3 shows the free end of the boom of Fig. 1, cut from A to A in Fig. 2, 30 appliances, viewed from above, and

Fig. 5 shows the weighing device according to Fig. 4 and the principle arrangement of the strain gauge sensors, Fig. 4, B - B

Fig. 6 of the cut-off O 35 115162 4 shows a weighing device and system according to a preferred embodiment, in block diagram form, for explaining the principle of operation.

The boom assembly 1 according to Fig. 1 comprises a first boom section, a pillar 2. The pillar 2 is generally vertical and arranged to rotate about a vertical axis Z1 (vertical Z) by a pivoting device 3 to which the first end 2a of the pillar is attached. The pillar 2 can also be mounted on a platform rotating about a vertical axis (vertical Z), which may also have a working cab. Boom 1 comprises a second boom section 4, the first end 4a of which is fixed by a horizontal joint 5a (transverse horizontal direction Y) at one end of the column 2. The other end 4b of the boom section 4 usually moves in a vertical plane (vertical Z and longitudinal horizontal X) rotating about the joint 5a. Rotation is effected by an actuator 6a coupled between the column 2 and the boom section 4. The boom 1 further comprises a third boom section 7, the first end 7a of which is connected to the end 4b by a horizontal joint 5b (horizontal Y). The free second end 7b usually moves in a vertical plane (vertical Z and horizontal X) about a pivot 5b. Rotation is achieved by an actuator 20b 6b coupled between the boom sections 4 and 7 by a link mechanism. The illustrated boom 1 is telescopically operable to extend the extension of the head 7b ···. so that boom section 7 has a sliding boom section 7c and ·· *. a boom section 7d sliding inside part 7c, which is controlled by a single actuator 6c and a chain mechanism (not shown). Boom head 7b working! *. The 25 bones 8 can thus be moved away from the implement. The tool 8 here is a loader which is attached to the head 7b by means of a rotator 9, which also corresponds to the attachment of the harvester head. The tool 8 is rotatably arranged around the vertical axis Z2 (vertical Z) by means of a rotator 9. Between the translator 9 and the head 7b there is still a removable cross cap [*: 30 pale 10 which allows for free hanging and rotation about the horizontal axes X1: '(horizontal X) and Y1 (horizontal Y) which are substantially perpendicular to each other. Parts 8, 9 and 10 typically have a combined weight of: · 300 kg and lifting logs typically have a weight of 300 to 1000 kg.

V ·: The boom shown has typically a lifting capacity of about 3000 kg, depending on 35 gauges.

115162 5

The application of the invention in various lifting and handling devices is easy, since the output from the measurement is as independent as possible from factors other than the load. In one simple, advantageous embodiment of the invention, the system is based entirely on calibration, whereby experimentally, levels of output signals corresponding to certain weights are found which can be used to determine other weights corresponding to other outputs, for example by means of a table or a formula. Known weights are used for calibration. The tool, which is part of the weight of the load and also causes a load, must also be taken into account when calculating the weight. The most accurate measurement is obtained when the load is at rest or moving at a constant speed. With the help of taring, the weight of the loader can be removed, for example. A table or a formula can be stored in the calculator of the measuring device, which displays the weighing results to the user. Alternatively, the calculation can be implemented in a machine control system, to which the output signals of the measuring device are connected via cabling and wiring.

When weighing a load, the various boom sections and load may be in motion, so accelerations must also be measured and taken into account in the weight calculation. Acceleration also gives an indication of the boom's operating status and working phase, so that the appropriate moment of measurement can be selected. When lifting. ···. acceleration occurs in the Z direction, where gravity also acts. With the telescopic boom • load, the load is also moved horizontally, whereby acceleration also affects the X direction. When turning the boom! The acceleration also affects the Y direction. In particular, the X and Z directions (vertical) are essential for the measurement. Maximum accelerations (2 to 8 g) can be measured or estimated based on boom dimensions, mass and actuator characteristics. Disturbances to measurement ai-V ·: especially caused by fast stops and accelerations. Travel speeds of 2 ”· 30 typically range from 5 to 15 m / s.

| ... In accordance with the invention, the forces acting on the boom member (at least in the X and Z 't' directions) are measured by means of sensors which measure? tense tension. The stress state is proportional to the effective load measurement and changes in it can determine the load or when the load is being handled. Preferably, the measuring point is located in a boom section projecting protrudingly from its first end and having a load suspended at its free end. The boom member is a load-bearing structure that is generally subjected to load bending in the vertical plane (X and Z directions) due to the gravity of the ground. Movement and acceleration give rise to additional forces and also non-vertical forces 5 which must be taken into account in the calculation and compensated for, which can be dynamic and the boom need not be stopped for the duration of the measurement. The stresses exert a proportional deformation on the material, preferably measured by strain gauges. Accelerometers 10 are also placed in the same device, depending on the measurement method. The change in deformation is proportional to the stress state and its changes.

The measuring point is located at the end of the outermost boom section, in the embodiment of Figure 1, at the end 7b of the outermost boom section 7 (preferably a half section 15d or equivalent, or boom section 7 without sections 7c and 7d). The boom 1 may also comprise one telescopic part 7d or only the boom part 7 and its end 7b. In addition, the boom member 7 is loaded by its own weight, which is located outside the measuring point, and by the weight of the crosspiece 10, the translator 9 and the loader 8, which must be taken into account in the calculation, e.g.

At the end, i.e. the tip piece 7b, the measuring point is at the point where the moment - .. * 2. the arm (distance between axis Y1 and measuring point) does not change substantially as the boom position changes and thus does not substantially affect the load. For example, there is no attachment between the shaft Y1 and the measuring point, or other support points (e.g., connection between the boom parts 7c and 7d), whose supporting forces would affect the load on the measuring point. Support forces vary, for example, with the gauge. The measuring point is: / ·; as close as possible to the axis Y1, whereby the portion of the boom part 7d which extends out of the boom part 7c can at the same time be shortened. The distance between the shafts Z1 and ./Z2 varies as the gauge changes, so that, for example, the loads on the boom sections 2 and 4 would vary even if the load was the same.

In the boom of Figure 1, the weighing device and measuring point are positioned at a point: 2: 35 in a piece 7b which is secured as a separate piece to a metal boom member 7d (or directly to the boom member 7), typically having a hollow square beam of 100-140 115162 7 mm. The tip piece 7b is, for example, a solid metal piece made by casting and having a recess in which the weighing device and the sensor means are well protected on all sides. The recesses extend approximately 50-100 5 mm in the longitudinal direction of the tip piece. The tip piece 7b is preferably secured to the boom part 7d by welding and has a cross-section corresponding to an I-beam having a central beam in the vertical plane and centered on the tip 7b and its axis of symmetry or neutral axis. At the same time, the center beam forms a vertical wall from which the desired deformation is measured. Further, the insertion of the tip piece 10 7b has the advantage that the other boom structure 1 need not be modified. As a welded structure, the tip 7b is, for example, a square beam. The boom section 7d is usually a hollow square beam.

The measuring point may also have a cross-sectional beam or otherwise be shaped 15. For the measurement, it is important to measure the forces acting in the X and Z directions, whereby the measuring point is not necessarily on a neutral scale but there are two measuring points on both sides of it symmetrically, for example on both sides of the tip piece 7b. A different measuring point is also often a prerequisite for using a ceramic resistor or piezoelectric resistor known per se. The measuring probe is attached, for example, to the projections that are created,. when H-shaped grooves and projections ··! · are formed on the sides of the tip piece 7b. pointing in the longitudinal direction of the tip piece 7b. Corresponding projections <> t \ can also be formed in the deeper tip piece 7b, the pre-! ; 25 for its neutral axis.

6 shows a weighing system according to a preferred embodiment, the weighing device 23 comprising sensor means 23a '·. ·: (For example, a strain gauge sensor 18-21 according to Figure 4), amplifiers 23b for amplifying measurement signals and computing means, as an integrated unit of processor 23c that can be reliably attached. The weighing device 23 further comprises the necessary protective housings and penetrations and may, as appropriate, consist of two or more -: * coarse housing and subassemblies for separate sensor sets: '2: 35 (e.g., 4 strain gauge sensors in each set). The processor 23c is arranged, on the basis of the measurement signals and by the desired weighing calculation algorithm, to compute the desired data, whereby it uses 115162 8 for example memory 23d for storing data. The calculation means 23c can also be located in the control system 24, whereby the device 23 provides one or more output signals which are used, as desired, to determine the weighing result. The operations of the computing means 23c can also be implemented in system 24, which can also be modified by software.

The more specific component selection and configuration of the weighing device 23 may vary. Preferably, the weighing device 23 can be connected to the boom 1 10 at a later stage, whereby it is connected to the other control and computer system 24 of the implement, for example by means of a field bus 23f. The bus 23f, for example the CAN bus (Controller Area Network), transmits the desired Input / Output signals. The exact configuration of system 24 varies from machine to machine. In particular, the out-15 of the weighing device 23 is the total weight of one or more lifted loads when the bodies are lifted in or out of the cargo space.

The following is Table 1, which shows the inputs and outputs 20 of a weighing device used in an extensive weighing system and calculation. Inputs are parameters, constants, or other measurement results that are taken into account in the calculation.

• 9 • v. Input / INPUT: power supply; kalibrointivakiot1); tarar constant 1); here \ calibration access code1); acceleration in the X, Y and / or Z directions; ! ! tension in the X and / or Z direction4) ._

Output / OUTPUT: load weight 2); X, Y and / or Z force 3); X-, Y- '···' and / or Z-acceleration 3); error or status code._

Explanation: 1) stored in the memory of the weighing device or control system: .i part of the calibration can also be done with HW; 2) one pound * ... * · result per lift; 3) Continuous or on demand 4) Can only include tension in the X direction._

Table 1 25 The weighing device 23 determines the weight of the load based on accelerations and / or changes in the stress caused by the load in the form of deformations of the wall structure, in particular the elongations measured by known strain gauges and electronic (e.g. The result can be determined computationally (SW), digitally in processor 23c and / or analogue (HW). Preferably, the result is presented to the user by means of the user interface means of the control system 24, the device 23 having suitable interface means (I / O module) 23e for connection to the fieldbus 23f. It is clear that the I / O may also comprise the measured force components, whereby the weighing result and other desired results can be calculated in system 24. The output signals useful for calibration are those which are load dependent. Parts 23c, 23d can be integrated with control system 10, which can also manage, record and store results as desired.

Figures 2 and 3 illustrate in more detail one preferred embodiment of the separate tip piece 11 (functionally corresponding to the tip piece 15 of Figure 1b), which is a continuous piece made by casting. At its first end 11c there are two adjacent vertical, plate-like flanges 12 and 13, between which the crosspiece is suspended from an axle pin (Y1 direction). On the left side 11a of the tip piece 11 and on the right side 11b, the second recesses, recesses 14 and 15, of substantially rectangular shape 20 are machined, where the tip piece 11 · *: · has a substantially l-beam having a vertical wall 25 the senses change as a result of the load. The sensors are arranged to • v. Measure the stresses in the vertical flange 25 to determine at least the X (tensile stress) and Z (shear stress) forces, so that *! Two sets of sensors are attached to the ends of the vertical flange 25 which are spaced apart in the longitudinal direction of the tip 11. Load Rack: · * ·: completely binds the I-structure, which acts as a load-bearing structure and transmits the load between the suspension means 12, 13 and the boom:. There are no other anchorage points between the load and the measuring point. The measuring point is between the ends 11c and 11d and laterally from the Y1 axis. Attachment to the vertical flange 25 is easy and can be reinforced with fastening, such as bolt or screw fastening 26. : * 'The depth of the opposing recesses determines the thickness of the l-beam and the stresses present. The tip piece 11 is secured to the boom member 16, which corresponds to the boom member 7 (more particularly part 7d) of Figure 1, preferably by welding, whereby the other end 11d of the tip piece 11 may have suitable shapes and fittings. The boom member 16 has a cross-section of 115162 10, typically a hollow square beam, into which the electrical conductors of the weighing device can be mounted in the shield if desired.

Figures 4 and 5 show a preferred embodiment of the sensor means comprising a vertically adjustable plate-like substrate 17 to which two sets of stretch tabs 18a-21a and 18b-21b are attached. In practice, there must be at least 4 strain gauges for one force component to compensate for interference. The base 17 is secured (bolt or screw fastening 27 at the corners) 10 to the vertical flange 25 of Figure 3, the deformation of which now 17 now follows. Thus, changes in the tension state of the tip member can also be determined. The strain gauges are electrically connected to the shape of the Wheatstone bridge as desired. At the output of the bridge, a voltage is obtained whose change is proportional to the change in the resistance of the strips, which in turn is known to depend on the elongation. It is well known in the art to attach stretch tabs, to arrange the necessary electronics, to protect them, and to more precisely dimension, balance, and select the bridge structure. The different directional components of the X- and Z-directional stress states can be determined with the help of different directional stretch strips. They can also compensate for the effect of temperatures on the measurement. Stretch • memory strips are positioned in the center of the base 17 to measure tensile (horizontal and vertical * * · t. ···.) Strips and shear stress (diagonal strips).

t · · • 1 · • I • »2: Let us now look at the more precisely applied measuring methods, where-! ] 25 is referenced in the following Table 2. The aim is to determine the X and • * · Z-directional forces Fx and Fz, which give the load: · «·; can be calculated as the resultant directly by their square sum expression, regardless of the position of the tip 11. If the boom is tilted · '/ ·, the force FY in the Y direction must also be considered, whereby the weight 30 is proportional to the root of the sum of the squares of their terms Fx, Fz and FY. With the weighing device and sensors shown, the field counts based on the measured quantities, so that other dimensions or position of the boom need not be taken into account.

»T r j 35 The entries 1), 2), 3) and 4) in Table 2 refer to the measurement methods which are briefly described. The desired combination of computational algorithms can be selected from the table depending on whether all 11516s are measured? 11 force and acceleration components, and depending on how the steps or sequence of operation of the boom are considered. The various combinations are obtained by combining one or more sensor types and their number to determine the required force components and 5 mm. to compensate for interference. Selected sensors provide the desired measurement result, which is used to determine the load. The calculation can be synchronized with other machine operations, thus improving the accuracy of the measurement result by the correct selection of the measurement moment and sufficient filtering of the measurement signals.

10

Measurement method: acceleration measurement and / or force measurement._

Sensor types: acceleration sensor 2) 3) 4); acceleration and gravity sensors3) 4); bonded stretch tabs1) 2) 3) 4); welded stretch tabs1) 2) 3) 4); separate strain gauges1) 2) 3) 4); integrated strain gauges1) 2) 3) 4) ._

Number: 0 - 2 (4), 3 (3) 4) (acceleration measurement); 1 - 3 pieces, 4 pieces 1) 2) 3) 4) (Vojmamjttaus) ._________________________

Measurement result: magnitude of acceleration 2) 4); X and Z components of acceleration 4); X, Y and Z components of acceleration3) 4); magnitude of force υ 2) 4). VOjman χ. and 2 components4); X, Y and Z components of force 3) 4): · Calculation of weighing result: force signal filtering 1); force · “*: average calculation 1); calculation of mean force, triggering based on acceleration 2); continuous force measurement and calculation (m = F / a) 3); triggering of angular difference between force and acceleration vectors (m = F / a) 3); measurement-. . selection of moment by cycle detection algorithm 4); calculation of the result with a work cycle memory algorithm 4); force and acceleration vectors * ··· 'point product3); calculation by impulse statement._

Table 2 I *

I I I

I «* a * <a>

In the first calculation method 1), only the force in the X and Z directions (vertical force components) or in the X, Y and Z directions is measured. Four strain strips for each force component a · are required for Mit-15 and the resultant force is calculated. For this resultan, an average can be calculated as a function of time, indicating the corresponding load of L, 1. Alternatively, to obtain an average, the signal corresponding to the power component 115162 12 is generated analogously and filtered to eliminate interference, thereby obtaining an average.

In the second measurement method 2) the calculation principle is otherwise the same as in method 5 1), but the calculation is started when the acceleration resultant (acceleration components in directions X, Y and / or Z) measured for acceleration is within predetermined limits, thereby avoiding incorrect measurement time during high acceleration or acceleration.

10 In the third method of measurement 3), three acceleration components and three force components are measured, on the basis of which the force and acceleration vectors are obtained in the desired X, Y, Z coordinate system. From the absolute value of the vectors, the load mass M is calculated either continuously or at certain times when the angular difference between the acceleration and force vector is within predetermined limits. Acceleration measurement may also include the effect of gravity. Mass M can also be determined based on vector algebra as a point product of force and acceleration, whereby only the component parallel to the measured force is taken into account from the acceleration.

20 In the fourth measurement method 4) the principle is that the weighing system recognizes from the measurement data what is in progress in the boom, and [::: deduces from the measurement or calculation results which moment the measurement result is most useful. The right moment of measurement is immediately recognized · Measurement results from the measurement results or boom are stored for analysis. The stored measurement data is analyzed at the desired moment, for example after the load has been unloaded, and the -: '. *! · * Is measured from the measurement data according to predefined criteria.

• · · • I · • ·. ···. The invention is not limited to the above embodiment only, but may be implemented within the scope of the appended claims. It is clear from the foregoing that the detailed processing, application and optimized integration of the measurement results into other weighing systems and machine control systems is clear. More detailed implementation. 35 may also vary according to the components and systems available.

Claims (20)

115162 13 A weighing system for determining the weight of a load handled by a lifting and moving device comprising a pivoting boom movable in a vertical plane (XZ) and an integral piece (11) fixed thereto for hanging the load and being loaded by at least vertical force; due to the weight of the suspended load, characterized in that the system comprises: 10. sensor means (23) attached to said tip piece (11), the output of which is one or more output signals (23b) proportional to the load caused by the load; 23c, 23d) arranged to determine a load weight corresponding to said output signals. System according to Claim 1, characterized in that the tip piece (11) is provided with a position on the sensor means (23) which is specifically intended for measuring deformation and which comprises means (25, 26) for attaching the sensor means (23). . «* * * • · • ·: v. System according to Claim 1 or 2, characterized in that the counting means (23c, 23d) can also be attached to the tip piece (11) either separately or together with the sensor means (23). • · · • · System according to one of Claims 1 to 3, characterized in that the tip piece (11) comprises means for hanging the load (30, 12, 13), the sensor means (23) being disposed between these means and the articulated boom. • » A system according to any one of claims 2 to 4, characterized in that said sensor means are for measuring the deformation of the material of the tip piece (11) 35, which is proportional to the load caused by the weight of the load. 115162 14 System according to Claim 2, characterized in that the sensor means (23) comprise stretch tab means arranged to measure the loads occurring in the vertical plane (X-Z). System according to Claim 6, characterized in that the strain gauge means are attached to a base, which in turn is removable! can be attached to the tip piece (11) so that the base follows the deformation of the tip piece (11). System according to one of Claims 1 to 7, characterized in that it further comprises sensor means for measuring the accelerations in the vertical plane (X-Z) and / or the horizontal plane (X-Y) of the tip piece (11), the output being one or more output signals proportional to the acceleration. System according to any one of claims 1 to 8, characterized in that it further comprises connection means (23e) arranged to connect a load indicating signal to the hoist and / or hoist and / or the implement to which the hoist / hoist is attached, oh-20 sensory system (24). A system according to any one of claims 1 to 9, characterized in that the counting means (23c, 23d; 24) are further arranged to sum and store the weights of the different processed loads. 25 A system according to any one of claims 1 to 10, characterized in that the computing means (23c, 23d; 24) is further arranged to continuously monitor said one or more output signals and determine for each load the time when the output signal 30 meets predefined criteria, and select the 2 * output signal at that time to use for weight determination. »· A system according to claim 11, characterized in that; ** the computing means (23c, 23d; 24) is further arranged to store 35 one or more output signals and to determine the time; section based on stored information. 115162 15 System according to any one of claims 1 to 12, characterized in that it also comprises user interface means for displaying the weight to the user and controlling the operation of the system. System according to one of Claims 1 to 13, characterized in that the tip piece (11) is integral with the articulated boom. System according to one of Claims 1 to 14, characterized in that it is an articulated boom of a load carrier. 10 A system according to any one of claims 1 to 15, characterized in that said sensor means are removably attached to said tip piece for replacement. A separate end piece for hanging loads to be attached to a lifting and transfer device, the end piece comprising a first end (11d) arranged for securing the end piece to an integral part of said device, being flexively loaded by at least vertical force due to the weight of the suspended load a head (11c) comprising means for hanging the load (12, 13), characterized in that a center (14, 15) is provided for measuring means in the middle part (11) of the tip piece; comprising means (25, 26) for said; v. for mounting the measuring device, said deformations being], '. 25 proportional to the load caused by the load. ; Tip according to Claim 17, characterized in that said position is provided in particular for securing the strain gauge means (23) of the measuring device (23) arranged to measure the loads V 30 occurring in the vertical plane (X-Z) in the operating position. Tip piece according to claim 17 or 18, characterized in that the tip piece (11) comprises a recess (14, 15) for mounting the sensor means (23). 115162 16 Tip piece according to one of Claims 17 to 19, characterized in that it is a tip piece to be attached to the articulated boom of the load carrier. * · •> I * • »» a * »* • * 115162 17