VEHICLE CRANE INSTALLATION WITH LIMITER MEANS

Abstract: Hydraulic truck cranes of the swinging jib type may potentially be operated in such an inappropriate manner that the truck may simply turn over. In order to prevent this, it is known to introduce certain operational limitations which will ensure the stability of the truck already when the bed of the truck is empty. However, skilled operators find such limitations unduly restrictive, in that for example by first placing a part-load at a suitable place on the bed of the truck, its is perfectly possible to continue by picking up another part-load which could not be loaded safely if the bed of the truck were empty. With the invention, this security problem is solved in a more naturalistic manner, in that the limitation means are not made operative until an inclinometer detects when the truck tilts to such a degree that there is a real risk of it actually tilting over. The inclinometer is arranged to be reset to zero by the truck assuming a natural tilt when standing on a non-horizontal support surface, such that a certain natural tilting of the truck will not, per se, introduce undue limitations or risk in the operational conditions.

Description: 1 Vehicle crane installation with limiter means The present invention concerns a crane installation on or for trucks, i.e. with a luffing-jib of the swing type which is operated hydraulically . In this connection it is well-known and directly prescribed to work with various safety measures and arrangements for safeguarding the stability of both the crane and the vehicle, in that e.g. a front-mounted crane may well have a long telescopic jib extending rearwards over the bed of the vehicle, while a simple swinging-out of the jib with a certain load to a transverse position can result in a tipping over of the whole vehicle if the length of the jib is not reduced beforehand to a certain safety value. Correspondingly, the vehicle itself can very easily become unstable if work is carried out with the jib of the crane swung forwards over the driver's cabin. The known security systems are based mainly on standard limitations which have been introduced regarding the operational capabilities of the cranes, e.g. with regard to the maximum permissible loads in different angular positions of the crane jib. The security factors involved are ones which pay extensive regard to possibly inexpedient operation of the cranes, which thus result in skilful and experienced operators simply considering the systems to be unnecessarily restrictive. In other words, these operators would be able to load and unload in a more suitable manner if they were allowed to do so, naturally while still not seriously endangering the stability of the vehicle. For example, it will not actually be necessary to work with a general limitation of a side load moment which, although enough to cause an empty vehicle to tip over, will however be fully acceptable if the operator has taken care beforehand to place a suitable load at the opposite side of the bed of the vehicle. 2 The present invention is based on the consideration that it is possible to introduce a more direct detection of when or to what degree the stability of the vehicle is actually in the danger zone, in that the detection means can thus be engaged - possibly after the signalling of an alarm - to activate the necessary and already known blocking means to prevent crane movements which could increase the element of risk. Such an arrangement would be to the satisfaction of all parties, in that the competent operators can presumably be- come even more competent, while the less competent will be provided with expert assistance in realising that by an inexpedient crane operation they are actually in the process of causing the vehicle to tip over. According to the invention, such a detection can in principle even be achieved in an extremely simple manner, i.e. by providing the vehicle with an inclinometer which is set to zero after the vehicle has been parked at the work site, after which it is ensured while working with the crane that the vehicle is not made to tip or tilt more than a pre- determined safety angle from the zero setting, respectively in the longitudinal direction ahead and possibly rearwards and to the respective sides. The relevant permissible safety angles can be indicated quite specifically as an expression that the vehicle is now actually close to being tipped over but, however, is consequently still stable. For example, it is well-known that the area in front of the driver's cabin is one of the more sensitive areas in connection with front-mounted cranes. When loading goods, it can be quite decisive that the operator begins by placing semi-heavy goods at the rear end of the vehicle bed, so that these loads will contribute towards the stabilising of the vehicle against tipping forwards when lifting heavier loads or loads at greater distances in front of the vehicle. An incompetent operator can in this connection quickly bring 3 the vehicle into the danger zone. It has been found that the said safety angle here will normally be only approx. half a degree. It is not necessary to carry out any registration of how the building-up of the load on the bed of the vehicle is effected, in that it is sufficient with a detection of the extent to which the half a degree is exceeded. In the lateral direction, the permissible angle of tilt can be somewhat greater, whereas it is hardly relevant to detect a tipping rearwards . In the event that the vehicle should "settle" slightly aslant or possibly in a more inclined manner while standing on the work site, it will be preferred that the inclinometer be set to zero at certain intervals, either with the crane unloaded in the idle position or - in order to maintain a certain margin of security - with the crane only moderately loaded during operation.. It applies in general that in the use of cranes of the aforementioned type, operations should not take place with the vehicle inclined at more than 5° from the horizon- tal, the reason being that the pivoting cranes are otherwise already subject to undesired influences in that their swing drive must thus carry out active lifting work. With the use of the inclinometer, it is expedient that this can thus also be used for a quite concrete deactivation of the crane when this angle is exceeded. However, it is a condition here that the inclinometer has merely been reset to zero while the vehicle is in the "practically" horizontal position, or that it is in operative connection with a spirit level . In the following, the invention is described in more detail with reference to the drawing, in which fig. 1 is a side view of a vehicle with front - mounted luffing-jib crane, and fig. 2 is a block diagram of a security system according to the invention, and 4 fig. 3 is a functional diagram of the surveillance effected in connection with a system according to the invention. Fig. 1 shows a lorry with a quite commonly-known luffing crane with a base 2, a crane column 4, an inner crane j ib 6 and an outer knuckle-jib 8, preferably of telescopic configuration, and pressure cylinders 10 and 12 for vertical pivoting of the respective jibs. The cylinder 10, which is designated the luffing cylinder and is the crane's main cylinder, is connected to a pressure transducer 14 which measures the load on the crane. The reference number 16 indicates a downwards-displaceable telescopic leg, which exists on both sides of the vehicle, mounted on a support-leg boom which is horizontally extensible so that the effective support breadth of the vehicle can be increased. In connection with a mounting bridge 18 down under the base 2, operation handles (not shown) are provided for the activation of the supply and reduction of hydraulic fluid to/from the crane's various control cylinders, including a not-shown cylinder for directing a turning of the whole of the crane around a vertical axis on the base 2. These operating handles are connected to sensing equipment 20 which can detect the operative position of each of the handles, or at least the most important of them. The reference number 22 indicates a "dump valve" which via a control unit can be activated to short-circuit the supply of oil to any relevant control cylinder, i.e. if it is detected that such an activation of a cylinder will re- suit in an overloading of the crane, so that this will be able to be detected by the main pressure transducer 14. According to the invention there is hereto added an inclinometer 24 which registers the inclination of the vehicle/crane, preferably in both the longitudinal and the lat- 5 eral direction. A control unit 26 will hereby be informed regarding the extent to which the crane can at all be operative with the vehicle inclined in the one or the other direction, and if this inclination is exceeded, the dump valve 22 can thus be activated for all functions or the hydraulic motor can be stopped. On the other hand, if the vehicle assumes an acceptably small inclination, complete functional capability can be maintained without disturbing restrictions. Hereafter, as mentioned above, it will be the inclinometer 24 which totally determines when precautions must be taken against a threatened tilting/tipping over of the vehicle, i.e. when it is registered that the whole vehicle chassis has already been tilted through a predetermined angle after the zero-setting of the inclinometer. Consequently, it is of no importance whether the vehicle stands at a certain angle from the start, which can even be greater than the change of angle which initiates the measures taken against function of the crane. During a calibration phase, the inclinometer detects a tilting in relation to the horizontal, and the crane is rendered totally inoperative if the angle is more than the permissible maximum, e.g. 5°. Even though work can be carried out with general directions for the size of the said critical tilting angles, e.g. with vehicles of different types, it is however preferred that in connection with each individual installation there is carried out a real testing and calibration after mounting of the individual vehicle and during use of the as- sociated support leg system. During this test it is examined when with a given angle position of the jib, and with increasing load moment, the vehicle will tilt so much that this angle of tilt must not be exceeded, and this angle is programmed into the control unit 26 with reference to said angle 6 position. The same procedure is repeated at a suitable number of other angle positions, so that as end result there will be programmed a picture of the variation of the critical angle of tilt all the way around the crane column. In that the con- trol unit 26 is constantly kept informed concerning the angular position of the crane, a correct critical angle of tilt will thus automatically be available for controlling the limitation system. Several different calibrations can be involved, e.g. in connection with a crane mounted on a vehicle for the transport of articulated trucks, where it can be relevant to program said tilting angles for the vehicle respectively with and without the semi -trailer . In the block diagram in fig. 2 it is seen that via a signal cable 26, the crane 4,6 sends its angle position to the control unit 26 , which also receives information from the sensor 14 concerning the crane load. From the beginning, the critical inclination angles for a number of different angle positions of the crane are fed into a memory unit 28, and for each angle of the crane the control unit will thereafter compare the actual signal from the inclinometer 24 with the related critical value, in that in connection with an actual operation a zero-setting (unit 29) of the angle signal will be carried out for correction for a possible sloping un- der layer for the vehicle, without the vehicle being influenced by any significant crane load. If during operations there is hereafter registered the critical angle of tilt in relation to the zero-set value, the blocking arrangement 22 for the relevant crane functions is activated. With reference to the diagram shown in fig. 3 for the surveillance and calibration function, it is continuously detected, preferably some times per second, to what degree the crane is "considerably loaded" (block 30) , by which is meant loaded in excess of a predetermined percentage of the maximum 7 load, e.g. 15-30% of the maximum. This is done to ensure that a calibration is not carried out with the vehicle in an "artificially tilted" position. Quite quickly after the start, it will be in the operator's interest that a situation is es- tablished with a load less than the predetermined amount, in that the calibration can then be continued. It is first checked (block 32) that the angle of the vehicle continues not to exceed the permissible maximum, for example by the vehicle being generally brought to tilt further during the work, i.e. if the ground on which the vehicle stands is not completely firm. If this happens, the function of the crane is stopped (block 34) . If the angle is in order, the surveillance continues to block 26, where it is examined whether the current load is greater or smaller than that at which a calibration was last carried out during the course of operations. If the load is smaller, the system continues with a new calibration (block 40) , though initially through a detection (block 38) of to what extent the crane is being manoeuvred. If the crane is idle, the calibration is carried out (operative zero setting of the inclinometer), but if it is in movement, a calibration is not carried out since in such case this could be encumbered with errors. In that the detection is effected several times per second, a calibration will be able to be established reasonably quickly, and it will be understood that the system will continuously seek to effect a re- calibration at the smallest load that the control unit has hitherto registered during the whole course of operations. It is envisaged that the operator can not bring the vehicle into any dangerous situation providing that the crane load does not exceed said value from block 30, i.e. work can be carried out with the crane without additional, special surveillance. With greater loads, the system continues from block 30 to block 42, where it is constantly detected (i.e. 8 while the crane is in movement) whether the actual tilting of the vehicle is less than the predetermined value for deviation from "calibrated zero" in the respective directions of tilt. Providing that this is the case, the work can continue without relevant restrictions in general. On the other hand, if the relevant relative angle of tilt is exceeded, the control unit will then initiate relevant restrictions such as a limitation in the swinging movement, block 44, which can be understood to be both a prevention of the swinging of the crane to an area of risk, as well as a reduction in the speed at which the crane can swing, since the crane inertia could in unfortunate cases result in the angle limit being exceeded to a disastrous degree. The possibilities which exist for further, relevant regulations (e.g. block 46) will not be de- scribed here in further detail, in that this can be left to professional evaluation.

Claims: C L A I M S 1. Crane installation on or for trucks, i.e. with a luf- fingjib of the swing type which is operated hydraulically, with means for limiting the operational possibilities of the crane during operating conditions which can give rise to the risk of instability of the vehicle, c h a r -a c t e r i z e d in that said limitation means are via a control unit in operative connection with an inclinometer for the vehicle, said control unit being arranged to activate the limitation means dependent on the inclinometer registering a critical tilting/heeling-over of the vehicle. 2. Installation according to claim 1, c h a r a c t e r i z e d in that the inclination measuring equipment is arran- ged for the registration of both longitudinal and transverse tilting of the vehicle. 3. Installation according to claim 1, c h a r a c t e r i z e d in that the inclinometer or the control unit is configured with an arrangement for effective zero-setting of the tilt registration in relation to the tilt of the vehicle itself, without or with only light crane loads in an actual working position of the vehicle, also while standing on a sloping under layer. 4. Installation according to claim 1, c h a r a c t e r i z e d in that said critical tilt/heeling is a predetermined magnitude which is ascertained by load trials with the vehicle . 5. Installation according to claim 4, where the crane is a swinging jib crane which is provided with equipment which registers the angular position of the jib in relation to the longitudinal axis of the vehicle, c h a r a c t e r i z e d in that the control unit has a memory unit in which the observed critical degrees of tilt for different angular positions of the jib are stored, and that this memory is used as a reference for comparison with the actual degree of tilt for a given angular position of the jib. 6. Installation according to claim 3, c h a r a c t e r i z e d in that the control unit is arranged for the conti- 10 nuous retrieval of said zero-setting with reference to the lowest crane load registered during a working operation. 7. Control unit for an installation according to claim 1, c h a r a c t e r i z e d in that it is arranged in accor- dance with any of the claims 1-6.

Inventors: JAKOBSEN MORTEN BRUUN, JAKOBSEN, MORTEN, BRUUN
Applicants: HOEJBJERG MASKINFABRIK A S, JAKOBSEN MORTEN BRUUN, HOEJBJERG MASKINFABRIK A/S, JAKOBSEN, MORTEN, BRUUN
Application year: 1999
Main classification: B66C23
IPC codes: B66C23