GB2271100A

GB2271100A - Method and apparatus for preventing a crane from tipping over.

Info

Publication number: GB2271100A
Application number: GB9321032A
Authority: GB
Inventors: Helmut Link
Original assignee: Iveco Magirus AG
Current assignee: Iveco Magirus AG
Priority date: 1992-09-19
Filing date: 1993-09-20
Publication date: 1994-04-06
Anticipated expiration: 2013-09-20
Also published as: BE1007515A4; JP3426299B2; ITTO930665A1; GB9321032D0; IT1261586B; NL194270B; GB2271100B; NL9301613A; FR2695925B1; JPH06263391A; NL194270C; DE4231441B4; FR2695925A1; DE4231441A1; ITTO930665A0

Abstract

Spring defections of the axes are braced by cable 11 and secured via hydraulic cylinder 6 before supporting beams 13 are extended. Pressure-tight check valves 10 prevent any slackening of this locking position. During a subsequent supporting operation the hydraulic reaction pressure applied in the spring locking cylinder 6 from the supporting operation is used as a control variable in respect of stability. The force S on the support leg 13 is simultaneously used as a control variable to determine stability. <IMAGE>

Description

2271100 METHOD AND APPARATUS FOR PREVENTING A CRANE OR A LIFTING RESCUE

VEHICLE FROM TIPPING OVER The invention relates to a method and apparatus for preventing a crane or a lifting rescue vehicle from tipping over by clamping and locking the wheel springs by means of a hydraulic springlocking device and extending out and arranging a supporting device on the ground by means of a control means.

With known spring-locking devices in vehicles the spring deflections of the axles are usually braced by cable control and secured via hydraulic cylinders before the supporting beams are extended is out. Pressure-tight check valves prevent any slackening of this locking position. Subsequently, the stabilising arms of the supporting device are extended into the corresponding position and brought into contact with the ground so as to provide an increased contact area in the desired firm ground region.

It is the object of the invention to devise a method and apparatus of the aforementioned type for preventing a crane or a lifting rescue vehicle from tipping over, wherein with simple means increased stability and, in particular, support control is reliably provided.

The object forming the basis of the invention is achieved by a method of the type indicated in Claim 1.

The method according to the invention is developed advantageously in accordance with sub-claims 2 to 6.

Claims

A preferred means for preventing tipping over for carrying out the method

according to the invention is characterised by the features of Claim

7. It is developed advantageously by the features of sub-claims 8 to 10.

The invention utilises the aforementioned known type of spring locking so that during a subsequent supporting operation the hydraulic reaction pressure applied in the spring locking cylinder from the supporting operation is used as a control variable indicating stability. If a definite value is assigned to the wheel remaining on the ground, when the stabilising arm is loaded on the unloaded side of the vehicle, this fixed value acts additionally on the spring-locking cylinder as an additional variable. The hydraulic pressure in the cylinder increases. This effect is utilised to protect the vehicle against tipping over by no longer allowing any load-increasing and moment-increasing control values. The proportional increase in the control variable offers the possibility of effecting a smooth control of the movement of the article.

Therefore, the means for preventing tipping over is applicable to vehicles with lockable hydraulic spring-locking devices on the axles and requires ground contact of the wheels. It protects the vehicle which has definite, established wheel pressures against tipping over in the usually endangered left-hand and right-hand side regions. In these regions the counterweights are small usually as a result of design constraints. The ground pressure exerted by the wheels, together with the static friction of the wheels on the ground resulting therefrom, stabilises the vehicle and this in particular in the special cases-of inclined positions and of dynamic impacts. The particular advantage of the invention lies in the fact that the measuring element is not arranged in a directly load-bearing support member of the supporting device.

The control operation for locking or smooth control of load and momentincreasing control values can be carried out both hydraulically, electrically, electronically and also together.

In a single-axle arrangement with two springs on each side of the axle. the following equilibria of forces occur at the tipping limit when no hydraulic preloading is generated in the spring-locking cylinders prior to the supporting operation: rear axle load = wheel load/2 = maximum cable 20 control force (which corresponds to the maximum hydraulic pressure in the cylinder). As a result of the residual load on the wheels on the ground, this load component induces a lower cable control force on the cylinders. Accordingly, a difference is possible between this and the maximum load. The simplest way is to take up the pressure in the cylinder by means of suitable pressure-tight electronic pressure sensors which are free of oil leaks. With the hydraulic preloading of the cylinders during the tensioning of the cable the maximum pressure in the cylinder increases by the increase from the reaction force of the spring by the preloading pressure.

The invention will be described in more detail below on the basis of one example of embodiment with reference to the accompanying drawings, wherein:

Figure 1 shows a view of the forces and moments in the lifting rescue vehicle with stabilising arms in one of the most critical lateral positions; Figure 2 shows an example of a spring locking device with cable control on a hydraulic cylinder, by means of which the spring of one axle is clamped, and Figure 3 shows the characteristic curve of the wheel spring during the bracing of the means for preventing tipping according to Figure 2.

Figure 1 shows a lifting rescue vehicle (1) with a supporting device (2) having stabilising arms and with a hydraulic spring-locking device (3) in one of the most critical lateral positions, in which it is illustrated how the outer supports on firm ground form the pivot point of the load moment or tilting moment M when the load L acts at the rescue cage of the rotating turret and the other side is raised "from the springs". The elasticity of the frame contributes to rendering the measured value effective prior to tipping and provides a further safety factor.

The means for preventing tipping over illustrated in Figure 2 is applicable to a crane or a lifting rescue vehicle which is provided with spring-locking devices (3) with hydraulic cylinders (6) and which exerts any residual wheel pressure of the vehicle wheels (7) on the ground (5).

The assemblies are usually mounted only on the rear axle or axles of the vehicle but can also be mounted on all the axles, i.e. are provided with spring-locking devices for each of the sprung axles.

Hydraulic spring-locking cylinders (6) may be used as the spring-locking devices (3), which are directed directly or, for example, by means of a cable control (11) with or without deflections against the elastic forces of the axles and wheels (7). Similarly, directly pivoted hydraulic cylinders may also be used which during the operation of the vehicle act as shock absorbers via throttle valves. These hydraulic cylinders are used for clamping and locking the wheel springs (4). This makes possible simple measurement of the reaction forces of the axle springs via pressure sensors (8) in the operating chamber (12) of the spring-locking cylinders (6).

If the normally loaded axle is braced by the spring-locking cylinders (6), this preload pressure induces in the operating chamber (12) an additional force on the spring (4) of the axle. If the vehicle is subsequently supported, the pressure in the operating chamber begins to rise as soon as the supports (13) have reached the ground (6). Before reaching the maximum value - the maximum can amount to the value:

pressure p = elastic force F/effective surface A of the cylinder (6) - the further support is stopped, with any desired low pressure. This pressure gives the remaining ground pressure or residual wheel pressure of the vehicle wheel (7).

The tipping device utilises the elasticity of the vehicle frame (14) so as to introduce a portion of the front wheel load as a further safety variable against tipping over.

The measured values in the hydraulic spring-locking cylinder (6) on the side opposite the load moment are increasing with the tilting moment M 5 up to the tilting limit.

Depending on the rigidity of the entire structure, on the axles secured and according to the chosen residual wheel pressure, the measured pressure forms a variable for the tipping over of the vehicle (I). According to the safety requirement, before reaching this pressure the further load- moment increasing movements are reduced or arrested by way of the microprocessor (9). This processing by means of the microprocessor (9) makes possible continuous monitoring with respect to the stability of the vehicle.

The pressure in the spring-locking cylinder (6) can be utilised directly to activate check valves (10) for limiting harmful control movements of the control means of the supporting device (2).

An important indication can also be obtained from the arrangement on the load moment side. Practically no pressure reduction should occur here, since this would signify a sinking of the support plate of the supports (13) on the ground (5). By means of the microprocessor (9), which stores the values of the shut-off pressure of the support at the start of operation, it is possible to carry out a constant comparison of the measured value from the locking cylinder (6) and the increase on the unloaded side and the decrease on the loaded side are monitored. For this purpose, the position of the stabilising arm is determined via a rotational 7 transducer.

With a device of this type it is possible to monitor the actual reaction from the supporting operation in the case of unknown ground conditions with a view to ensuring stability.

Therefore, the spring (4) of the axle is clamped according to Figure 2 by means of a cable control (11) which is connected to the spring-locking device (3). The bracing is carried out before any supporting operation of the vehicle so as to achieve a definite starting basis. In this context the axle load H and the preloading pressure p of the hydraulic cylinder (6) of an assembly with a cable control 11 come into consideration for tensioning the cable.

As illustrated in Figure 3, the spring deflection s and the axle load H are in a major correlation to one another and the example shows a spring with a parabolic characteristic curve. The preloading force V generated by the hydraulic pressure p acts additionally on the spring (4) of the axle. When pressure is being relieved as the wheel is raised, the elastic force F and the preloading force V produce the maximum pressure in the cylinder.

If greater accuracy is required in inclined positions, the inclination of the vehicle (1) can be taken for axle load or wheel load correction, calculated by microprocessor and assigned to the individual wheels as a correction value variably for limiting the control movement.

All the novel features mentioned in the description andlor illustrated in the drawings, 0, either taken alone or in a suitable combination, are essential to the invention even if they are not expressly claimed in the claims.

CLAIMS:

A method of preventing a crane or a lifting rescue vehicle from tipping over by clamping and locking the wheel springs by means of a hydraulic spring-locking device and extending out and arranging a supporting device on the ground by means of a control means, wherein a residual wheel pressure of the vehicle on the ground is established by clamping the wheel springs by means of the spring-locking device, during a subsequent supporting operation the reaction pressure applied in the spring-locking cylinder is used by a control device as a control variable indicating the stability of the vehicle, and is with a load S on the stabilising arm of the supporting device on the unloaded side of the vehicle the residual wheel pressure acts on the spring-locking cylinder as an additional variable.
2. A method according to claim 1, wherein by loading the spring-locking cylinders with a definite hydraulic pressure the variable for a reaction force from the wheel spring of the axle in the spring-locking cylinder initially takes the form of a hydraulic pressure p, which in the supporting device in the actual load condition on the unloaded side, the pressure p corresponding to the maximum measurable reaction pressure when the wheel is fully relieved of load, which is measured by means of a pressure sensor and is stored in a microprocessor as a comparison variable with respect to the instantaneous value, which results from the residual wheel pressure, and forms a measured value of the unloading of the wheel with respect to the tilting moment, and in that before reaching the tilting limit the microprocessor reduces the load-moment increasing control movements and arrests them when it is reached.
3. A method according to either claim 1 or claim 2, wherein a rotational transducer on the rotating turret of the crane or lifting rescue vehicle indicates to the microprocessor the actual load direction for the evaluation of the wheel side.
4. A method according to any one of claims 1 to 3, wherein the microprocessor also arrests load-increasing control movement on the loaded side before dropping below a pressure determined during the supporting operation and additionally triggers a warning device.
5. A method according to any one of claims 1 to 4, wherein the reaction pressure in the spring-locking cylinder acts on the control means partly hydraulically, pneumatically, partly electronically/ electrically alone or in combination, and prevents the load-increasing control movement or allows a load-decreasing control movement.
6. A method according to any one of claims 1 to 5, wherein in vehicles with admissible inclined positions the axle load distribution is corrected by way of the calculation of the centre of gravity of the vehicle and the reaction forces from the axle springs correct the errors from the inclined position.
7. A means for preventing tipping over for carrying out the method according to any of claims 1 to 6, wherein a rotational transducer is provided on the rotating turret of the crane or lifting rescue vehicle, which by way of an output signal activates the microprocessor with a view to indicating the 11 actual load direction for the evaluation of the wheel side.
8. A means for preventing tipping over according to claim 7, wherein the microprocessor activates an arresting device of the control means for the purpose of arresting load-increasing control movements and additionally a warning device so as to trigger a warning signal, when a given pressure value is not 10 reached on the load side during a supporting operation.
9. A means for preventing tipping over according to either claim 7 or claim 8, wherein a check valve is is provided which is directly activated by the reaction pressure in the operating chamber of the spring-locking cylinder, and in that the activated check valve arrests the hydraulic drive means of the supporting device so as to prevent load-moment 20 increasing control movements.
10. A means for preventing tipping over according to any one of claims 7 to 9, wherein it is mounted at least on individual wheels independently of the 25 number of vehicle axles.
11. A method substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings. 30
12. A means for preventing tipping over substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings. 35