WO2003064311A1

WO2003064311A1 - Load control system, preferably for boom cranes

Info

Publication number: WO2003064311A1
Application number: PCT/DK2002/000801
Authority: WO
Inventors: Per Holm Hansen
Original assignee: Hojbjerg Maskinfabrik AS
Current assignee: Hojbjerg Maskinfabrik AS
Priority date: 2001-11-28
Filing date: 2002-11-28
Publication date: 2003-08-07
Anticipated expiration: 2004-05-28
Also published as: ES2536454T3; EP1490288A1; DK1490288T3; EP1490288B1

Abstract

For counteracting the overloading of hydraulic truck cranes (4) beyond their nominal load capacity there is often used a load control system (2), typically connected to one or more measuring devices (22) for measuring pressure disposed at relevant points on the hydraulic system of the crane, where e.g. a measured pressure in the load control system is transformed to an actual load that is compared with the maximum allowable limit, and in case of exceeding the limit, the load control system activates a dump valve (17) whereby further operation within a stop situation (stop period) determined by the load control system is rendered impossible. A load control system of the kind indicated, including a calculation unit, which, before an operation called by the operator is effected, performs a consequential assessment of this operation. Via information in an information centre (24) associated with the load control system and possibly including a remote control unit (28) for controlling the functions of the crane, the operator may determine whether further movement is possible, thereby optimising the operational capacity of the crane. Hereby unintended stop situations, in which operation of the crane functions are impossible, are avoided.

Description

Load control system, preferably for boom cranes

The present invention concerns a load control system with a readout for hydraulic truck cranes of the kind placed on a lorry or a trailer, and comprising a column rotating about a base, and a boom arrangement connected to the top of the column, predomintantly used for loading and unloading of the vehicle loading platform, and a valve block connected to electric switches that control supply of oil under pressure to the hydraulic cylinders of the crane, and where the load control system is connected to a relevant signal transducer for registering the instantaneous values of hydraulic system pressure, which in the control system are transformed to a load, and where the load control system in case of loading the crane beyond its nominal load generates limitations in the functions of the crane.

Such a load control system is known from WO 97/29038, where the load control system comprises a control unit permanently mounted on the crane itself, typically in the area where manual control of the crane functions is taking place, at the front of which a line broken by light emitting diodes is marked, which displays the actual load of the crane in 5% increments, from 80% to 100% load.

The said units also comprise an acoustic signal emitter which in case of loading the crane immediately below and beyond its nominal value activates a sound signal so that the operator of the crane is informed that he is about to load the crane to a level that is not permissible relative to the nominal load capacity of the crane.

The load on the crane is registered by a signal transducer on the main cylinder of the crane which is registering the current pressure in the main cylinder which is transformed into an actual load situation for the crane in the calculation unit of the load control system, and in case that the actual load situation exceeds the permissible value for the crane, the load control system activates a so-called dump valve that renders impossible any further operations of the crane, however in a manner permitting load reducing operations with the crane only. The described load control system only opens the possibility of following the current load of the crane as a whole in the upper range around the nominal load capacity of the crane by providing signals in the form of switching the previously mentioned light emitting diodes on and off. The load control system furthermore relies on previously occuring actions, even though there is incorporated a certain pedagogic regarding load capacity of the crane in the nature of the load control system, particularly its maximum nominal load capacity.

Furthermore, the attention of the crane operator will hardly be directed towards the load control system box with the aforesaid light emitting diodes which present the stepwise current load of the crane around its nominal load capacity, but rather on the handling situation itself with the burden suspended by the crane hook.

It is the purpose of the invention to provide an informative load control system that will considerably reduce the number of stop situations, as the operator via information may avoid unintended stop and limitation situations. This provides the operator with better overview and knowledge of the lifting capacity of the crane in various load situations.

This purpose is achieved by a load control system of the kind indicated in the introduction, which is characterised in that the load control system is connected to the electric switches of the valve block and is arranged with a calculation unit in such a manner that functions/operations of the crane called by the operator are checked in the control unit in relation to the nominal load capacity of the crane, before they are initiated/realised by regulating valve settings in the valve block through activation of the electric switches, and that a display, which is accessible for the operator in an information centre communicating with the control system, shows analogous values between 0 and 100% and/or real values in measurement units, each analogous value being an accurate expression of the current load as measured on relevant components on the crane.

Hereby, several advantages are achieved. Firstly, it is achieved that the operator is supplied with visual information on a running basis regarding the current load situation of the crane and other important information regarding the operation of the crane. This means that the operator may follow the current load on the crane simultaneously with manoeuvring the burden handled by the crane and thus avoid load exceeding operations that will entail limitation and stop situations. Like the driver in a car e.g. monitoring the speed via the dashboard of the car in order to ensure that the speed of the car does not exceed a relevant speed limit, thereby avoiding fines incurred for speeding, the crane operator may continuously observe various important information on the information centre display about the operation of the crane, including whether the current load of the crane is approaching the maximum nominally permissible load of the crane, the exceeding of which results in inexpedient stop and limitation situations.

The system thus provides hitherto unknown possibilities for safeguarding the crane operator and others involved in the work against the occurrence of the said inexpedient stop and limitation situations as a consequence of not having the possibility of knowledge about the current load of the crane, and furthermore for giving the crane operator a possibility for manoeuvring the crane to its absolute maximum.

Furthermore a preventive load control has been achieved, consisting in that intended operations of the crane are evaluated by the load control system before these are initiated, and that the crane operator is advised in advance before a load exceeding operation of the crane that may entail a stop situation, so that the operator can choose an alternative operation of the crane that does not result in a stop situation.

The operator may furthermore, via visual as well as acoustic information in the information centre, avoid unintended stops as the values of the relevant operation parameters are indicated in the information centre. The information is preferably indicated in %, alternatively as analogous proportional magnitudes.

Such a load control system warning the operator before a load excess occurs will have the consequence that the operator (and possibly his helpers) in many cases may avoid stop situations whereby there is achieved a great possibility of savings in the time used in connection with the use of the hydraulic truck crane as well as a maximum utilisation of the capacity of the crane.

With the purpose of giving the operator better possibility of following the actual load of the crane, the load control system may be disposed such that the display can be set to show all relevant data concerning the crane (parameters of operation, use and safety), which are registered by the control system. Hereby it is achieved that the operator may continuously be informed of the actual load on the various parts of the crane. That may be magnitudes of the load on the main cylinder of the crane, the cylinders on the other parts of the crane, e.g. a fly jib, and possibly in special cases where the crane is provided with a winch, the load thereon compared to its nominal load.

Thus it will now be possible for the operator to optimise the operation of the crane and thereby utilise its load capacity maximally, because the operator will be able to continuously supervise the magnitude of the load on various parts of the crane, and in case one part of the crane approaches the nominally permissible load, the operator will have possibility of performing compensating operations that reduce the load at the critical point and in this way optimises the use of the crane.

In connection with the use of truck cranes it will be very expedient indeed if the operator has a certain freedom of movement, so that during the operations of the crane he may be situated so as to have a complete overview over the load with which the crane is operating. With the purpose of improving the operator's conditions while simultaneously following the actual load situation of the crane, the information centre containing the display may furthermore comprise a remote control unit with a control panel including control keys for operating the functions of the crane, the remote control unit communicating with the crane via a transmitter-receiver unit (electronics box) on the crane, a load control system and electric modules connected thereto connected to the valve block for controlling/regulating its valves and thereby the functions of the crane as indicated in claim 3.

Hereby it is achieved that the operators of the crane may arbitrarily choose their positions relative to the crane and its load, so that it in practice they may be very close to the location where the load is to be set down/picked up by the crane, which will give a possibility for a more precise placement of the load handled by the crane, all the while the operator may continually follow the current load on the different parts of the crane via the load control system. With the purpose of drawing the operator's attention to possible undesired stop situations before these arise and when these have arisen, the information centre may include an acoustic signal emitter as indicated in claim 4.

Sometimes it will be expedient for the operator to follow other relevant operational data than the current load, or simultaneously therewith, and a possibility is provided therefor when the information centre according to the invention is adapted to show different parameters in the form of display images with icons and corresponding values and units in the form of analogous values, or relative values between 0 and 100% on its display, the values each being a precise indication of the actual load or other important parameters measured on relevant components of the crane, and switching between the display of respective display images by actuating a switch on the control panel of the remote control unit.

For the sake of clarity, the respective display images will comprise few and simple information elements/icons, but it is preferred that on each display image there may be shown at least two different parameters concerning the crane.

With the intention of quickly giving the operator relevant information before exceeding the nominal load, the load control system will be adapted so that any kind of alarm arising during operation of the crane, will cause an automatic switch to displaying the image relevant for the alarm concerned on the display of the information centre.

Signals between load control system and information centre and the remote control unit may be transmitted wirelessly or via cable as signals which via a receiver in the information centre informs about its icons/values and units on the display of the information centre.

By combining the information centre and the remote control unit for operating the functions of the crane, there is thus provided the possibility that the crane operator may freely position himself optimally with regard to a clear view in connection with the operation of the crane, while simultaneously he may continuously supervise operational and load data from the load control system of the crane. By means of the information centre according to the invention there may thus be achieved optimal conditions for the crane operator and the possibility of optimal utilisation of its capacity concurrently with the safety conditions being optimal as regards visual control of the handling of the load handled by the crane and with regard to monitoring the load on the crane and other operational parameters for it.

With the purpose of ensuring the load control system against unintended operations of the crane in case of a too low energy level in the battery of the remote control unit, where the information centre and the remote control unit are supplied with energy from a battery in the information centre, the status of said battery being continuously monitored and registered, respectively, in the information centre, and a signal concerning battery status being transmitted wirelessly or via cable to the load control system that is adapted so that the remote control unit is rendered inoperative in ease of a too low energy level in the battery, and in order that an alarm for this event is shown on the display and transmitted from the load control system to the information centre before the remote control unit is rendered inoperative.

Hereby is achieved that in good time before a too low battery level occurs, the operator is given a possibility of performing a switch to a fresh/newly charged battery, so that change of battery will not occur in a critical load situation for the crane.

It is to be noted that warning panels for truck cranes are known, where the panel includes an image of the crane concerned in the form of a diagram, including its hydraulic cylinders, where light emitting diodes on the marking illustrating the hydraulic cylinders are inserted in a row and are lit successively, where these indicate different levels of load of the crane parts, but stepwise, like in the load control system of the type described in the introduction. Such a warning panel is known from EP Al 146006. However, the warning panel disclosed in the said EP patent publication does not provide the same precise indication regarding the precise current load of the crane, just as the said system does not include a calculation unit performing a test of the operations of the crane intended before these are initiated. Frequently there will be a need for determining the weight of a body to be handled by the crane. This may be relevant in connection with the placement of the crane in relation to the place where the body/burden is to be placed. Normally, in connection with weight determination, a crane hook is used with an incorporated weighing cell which is connected to a display that indicates the weight of the body to be lifted. Such weighing cells are, however, relatively costly, and furthermore such weighing cells also need to be serviced.

With the purpose of performing weight determination for a body suspended in the crane hook, the load control system may be adapted so that it incorporates a special weight determining function for a body suspended from the crane hook after placing the boom system of the crane in one or more reference positions from which the calculation unit of the load control system calculates the weight of the body from relevant signal transducers in the hydraulic system and transmits the signal wirelessly or via cable to the information centre, where the calculated weight of the body together with a relevant icon for weight determination are displayed.

Hereby the possibility of dispensing with the aforementioned weighing cell, being also relatively expensive, may be achieved,. It may be difficult for the operators to remember the completely exact reference position in connection with weight determination of the burden/body suspended from the crane hook. The load control system may therefore be adapted so that the said reference positions for placing the boom system of the crane in connection with weight determination of the load suspended in the crane hook and are pre-programmed in the load control system and may be called by means of a key arranged therefor on the information centre. However, it is to be noted that the operator may intervene at any time against dangerous situations in connection with automatic operations to be performed by the crane after a reference position for weight determination has been called from the remote control unit, so that the operator at any time has the opportunity of intercepting possibly dangerous situations in connection with crane operations and to counteract unintended stop situations for operations of the crane.

The invention is explained in more detail in the following with reference to the drawing, where: Fig. 1 schematically shows a load control system according to the invention for a truck crane, and where

Fig. 2 shows a concrete embodiment of a truck crane with a load control system with a remote control unit according to the invention, and

Figs. 3 A - 3C are examples of information centre displays in connection with the load control system.

In Fig. 1 is shown in schematic form a truck crane 4 on a lorry 6, where the truck crane includes a base 8 with a rotatable column 10 standing up therefrom and a boom system 12 which is suspended at the top 14 of the column. The truck crane 4 furthermore includes a valve block 16 comprising electric switches 18 communicating with valves 19 that in turn communicate with the hydraulic cylinders 20 of the crane via pipes 21.

The load control system 2 is, as seen in Fig. 1, connected to a pressure transducer 22 via a cable connection 23, and furthermore the load control system 2 is connected to an electronics box 25 which in the shown embodiment, cf. also Fig. 2, has a wireless connection to an information centre 24. Furthermore, in the information centre 24 a remote control unit 28 is incorporated for controlling the functions of the crane that in the embodiment shown communicates with the electric switches 18 in the valve block 16 via the wireless connection and the electronics box 25.

The remote control unit 28 incorporated in the information centre 24 includes a control panel 29 with control keys 30, and the information centre also comprises an acoustic signal emitter 34 and a display 27 as well as a switch 38 for changing between different displays in the form of images 36 on the information centre 24.

The load control system 2 is adapted so that at any time during the operation of the crane it will decide whether operations with the crane are feasible, and will trip stop situations in case that the load on the crane is reaching its nominal load capacity. This means that all called operations of the crane are monitored, irrespective whether these are effected from the remote control unit 28 by activating the control keys 30 or are effected by manual activation of the valve 44 of the valve block.

The control unit 2 is thus performing two tasks, of which the first is monitoring the current load on the relevant functions of the crane by receiving data from pressure transducers 22 that are disposed at relevant points on the crane 4. The other task performed by the load control system 2 is that it further performs an advance calculation of the load consequences of operations called for regarding the crane. These advance calculations are activated in the control system 2 by activating the control keys 30 on the remote control unit 28 incorporated in the information centre 24.

The load control system 2 is thus transmitting signals back to the information centre 24 via the electronics box 25. These signals are transformed and shown on the information centre 24 of the remote control unit, where the operator may choose between different display images 36 concerning the current operational data from the crane. Typically, the data preferred will mostly be current load data regarding the load on the different parts of the crane as outlined in Fig. 2. In case that an intended operation of the crane 4, called by the keys 30 on remote control unit 28 integrated in the information centre 24 and implying exceeding of the maximum allowable load of the crane according to the calculation unit in the load control system 2, a signal is transmitted to the information centre 24 and is shown on its display 27 as a warning, typically combined with an automatic switch to an image of this, showing the parameters for the relevant overload situation, and activation of a warning lamp, and/or by activation of the acoustic signal emitter 34 on the information centre 24.

In case of a called operation of the crane that will cause exceeding of the maximum allowable load, in the shown embodiment the load control system will furthermore transmit a signal to the information centre 24 of the remote control unit via the electronics box 25 so that the intended load exceeding action is shown as a warning alarm 10 and with an indication that the alarm is of a preventive character.

The load control system 2 according to the invention furthermore has the property that it can perform determination of the weight of a burden 42 which is suspended in the crane hook under the condition that the boom system 12 of the crane has assumed a reference position from which the calculation unit (not shown) of the load control system will transform signals from the pressure transducer 22 on the hydraulic cylinder of the crane into a weight which is read out on the display 27 on the information centre 24 when this display is chosen in the information centre, cf. Fig. 3 A.

Examples of some of the other possibilities for showing current analogous data concerning the crane operation on the information centre display 27 are shown in Figs. 3 A and 3B, respectively indicating actual load on the crane and the current pressure in the hydraulic system (typically measured in the main cylinder of the crane).

The information centre 24 furthermore includes light emitting diodes 44, 46, 48 which are activated during different operational situations of the truck crane, e.g. the diode 44 may have a green colour indicating that the crane may be operated, the diode 46 may have a yellow light in case of reduced oil flow or support legs operations, and the diode 48 may have a blue light for signalling an impending safety interference from the load control system.

By means of the load control system 2 according to the invention there is thus indicated a preventive system which warns the operators of the crane truck 4 in advance of performing load exceeding actions that may entail stop situations. Furthermore integration of the remote control unit 28 in the information centre 24 implies that the operator can follow the actual value of the load on the individual parts of the truck crane while the operator may also be able to physically dispose himself in relation to the burden 42 handled by the crane (cf. Fig. 2), that the handling may be continually visually supervised so that dangerous operations of the crane/load may be avoided. The crane operator, provided with a load control system according to the present invention, will thus eventually achieve much routine in operating the crane in order to utilise its load capacity to the utmost without activating the stop function of the load control system.

List of reference numbers: : load control system : truck crane lorry : base 0 column 2 boom system 4 top of column 6 valve block 8 electric switches in (16) 19: valves 0 hydraulic cylinder (21): pipe 2 signal transducer (pressure transducer) 3 cable between (2) and (22) information centre 5 electronics box 6 acoustic signal emitter 7 display on information centre (24) 8 remote control unit integrated in information centre (24) 9 control panel on remote control unit (28) 0 control keys on remote control unit (28) 2 electric modules acoustic signal emitter on information centre (24) 6 display image on information centre (24) 8 switch on information centre (24) for changing between different display images crane hook burden in crane hook light emitting diode on information centre (24) light emitting diode on information centre (24) 8 light emitting diode on information centre (24)

Claims

P A T E N T C L A I M S

1. Load control system (2) for hydraulic truck cranes (4) of the kind placed on a lorry (6) or a trailer, and comprising a column (8) rotating about a base (10), and a boom arrangement (12) connected to the top of the column (14), and a valve block (16) connected to electric switches (18) that control supply of oil under pressure to the hydraulic cylinders (20) of the crane, and where the load control system (2) is connected to at least one relevant signal transducer (22) for registering the instantaneous values, e.g. of pressure in the hydraulic system, which in the control system (2) is transformed into a load, and where the load control system (2) in case of loading the crane (4) beyond its nominal load generates limitations in the functions of the crane in a (so-called) stop or penalty period during which the system renders impossible further operations with the crane (4), e.g. by activating a dump valve (17) in the hydraulic system of the crane, c h a r a c t e r i s e d i n that the load control system (2) is connected to electric switches (18) of the valve block and is thus arranged with a calculation unit that functions/operations of the crane (4) called by the operator are checked in the control unit in relation to the nominal load capacity of the crane, before they are initiated/realised by regulating valve settings in the valve block (16) through activation of the electric switches (18), and that a display (27), which is accessible for the operator in an information centre (24) communicating with the control system (2), show analogous values between 0 and 100% and/or real values in measurement units, the values each being an accurate expression of the actual load as measured on relevant components of the crane.

2. Load control system according to claim 1, c h a r a c t e r i s e d i n that the information centre (24) during operation of the crane (4) may be set to show all relevant data concerning the crane (4) (operational, use, and safety parameters), registered/calculated by the load control system (2) on its display (27).

3. Load control system (2) according to claim 1 or 2, c h a r a c t e r i s e d i n that the information centre (24) for showing analogue values measured by the control system in the display (27) further includes a remote control unit (28) with a control panel (29) including control keys (30) for operating the functions of the crane.

4. Load control system (2) according to any of the claims 1-3, characterised in that the remote control unit (28) comprises an acoustic signal emitter (34) controlled by the load control system (2) of the crane, the acoustic signal emitter (34) being activated when an overload situation is imminent or has occurred.

5. Load control system (2) according to any of the claims 1-4, characterised in that the information centre (24) is arranged for showing different parameters in the form of displays (36) with icons and values related thereto and units in the form of analogous values, or relative values between 0 and 100% on its display (27), which values are each a precise expression for the actual load or other important parameters measured on relevant components of the crane (4), and the respective display images being switched by actuating a switch (38) on the control panel (29) of the remote control unit.

6. Load control system (2) according to any of the claims 1-5, characterised in that on each display image (36) the value of at least two different parameters concerning the crane (4) may be shown.

7. Load control system (2) according to any of the claims 1-6, characterised in that it is adapted so that any alarm occurring during operation of the crane (4) will cause a switch to the display image (36) relevant for the alarm in question in the display (27) on the information centre (24).

8. Load control system (2) according to any of the claims 3-7, characterised in that signals between the load control system (2), the information centre (24) and the remote control unit (28) are transmitted wirelessly or via cable as signals which by a receiver in the information centre (24) are transformed into icons, values, and units on the display (27) of the information centre (24).

9. Load control system (2) according to any of the claims 3-8, characterised in that the information centre (24) and the remote control unit (28) are supplied with energy from a battery in the information centre (24), the status of said battery being continuously monitored and registered, respectively, in the information centre (24), and a signal concerning battery status being transmitted wirelessly or via cable to the load control system (2) adapted in such a way that the remote control unit (28) is rendered inoperative in case of too low energy level in the battery, and in order that an alarm for this event is shown on the display (27) and transmitted from the load control system (2) to the information centre (24) before the remote control unit (28) is rendered inoperative.

10. Load control system (2) according to any of the claims 1 - 9, characterised in that it includes a special weight determining function for a body (42) suspended from the crane hook (40) after placing the boom system (12) of the crane in one or more reference positions from which the calculation unit of the load control system calculates the weight of the body from relevant signal transducers (22) in the hydraulic system and transmits the signal wirelessly or via cable to the information centre (24) where the calculated weight of the body (42) together with a relevant icon for weight determination are read out from the display (27).

11. Load control system (2) according to any of the claims 1-11, characterised in that the information centre (24) further includes a number of light emitting diodes (44, 46, 48) that are activated by the load control system (2) at different load situations/operations of the truck crane (4).