EP1911717B1 - Jib position indicator for crane - Google Patents

Description

The present invention relates generally to the technical field of cranes. More particularly, this invention relates to a device for indicating the position in space, that is, of the orientation, of the boom of a tower crane or a luffing jib crane.

A tower crane taken here as an example has, in a generally known manner, a distributing boom which, thanks to a motorized rotation mechanism, is orientable about a vertical axis, so that this boom pivots in a horizontal plane. The boom can thus be pivotally mounted at the top of a fixed crane mast, in which case the rotation mechanism is at the top of the mast. In other crane embodiments, the boom is integral in rotation with the mast, the rotation mechanism being in this case at the base of the mast of the crane.

In order to prevent the boom of a crane from accidentally coming into contact with a fixed or moving obstacle, for example with another relatively close crane, it is already possible to use so-called anti-collision safety systems, such as, for example, the crane interference detection system described in the patent French FR 2458504 . Such a safety system aims to stop the rotation of the boom of the crane, before it encounters an obstacle. For this purpose, it is necessary to determine at all times the position of the rotating part of the crane in space, and for this the crane must be equipped with a specific indicator device capable of detecting the instantaneous angle of orientation. of the arrow.

In practice, the measurement of the angle of rotation of the boom of a crane is carried out by means of an angular sensor which may be a potentiometer or an encoder or any other equivalent sensor, analog or digital type. Such an angular sensor is rotated by means of a pinion, which meshes with a ring gear which belongs to the rotation mechanism which equips the crane.

Such an example of a sensor is shown in the document US 3,760,401 .

Thus, during the rotation of the boom by the aforementioned motorized mechanism, the angular sensor such as potentiometer is itself rotated by a shaft rotating at an angular speed multiple of that of the arrow in the reduction ratio. R of the crown / pinion gear set, ie R = D / d if D designates the number of teeth of the crown, and d the number of teeth of the pinion (here it is more particularly a multiplier ratio, the pinion turning faster than the arrow itself).

• Une première solution, purement mécanique, consiste à insérer pour l'entraînement en rotation du capteur un jeu d'engrenages supplémentaire, de rapport inverse au rapport R = D/d (rapport couronne/pignon) précédemment mentionné. Ainsi, le capteur angulaire tourne en synchronisme parfait avec la flèche de la grue, c'est-à-dire que le capteur décrit lui-même exactement un tour complet, pour un tour complet de la flèche. Dans ce cas, toutefois, le système est spécifique à chaque couple pignon/couronne et, même si ce système n'introduit aucune erreur de mesure grâce au parfait synchronisme de rotation entre le capteur et la flèche, un tel système n'est certainement pas universel compte tenu de la variété existante de couronnes et de pignons.
• Une deuxième solution, autorisant une certaine variété d'utilisations, consiste à prédéfinir un certain nombre de couples standardisés couronne/pignon, à chaque couple correspondant un rapport R = D/d qui peut être un nombre quelconque. Le capteur angulaire tel que potentiomètre, dont la rotation est liée à celle de la flèche, totalise ainsi un nombre de tours (Nc) de ce capteur lui-même. Un calculateur intégré, connaissant le rapport R du jeu d'engrenages (R = D/d soit : nombre de dents de la couronne / nombre de dents du pignon), en déduit le nombre de tours (Ng) effectué par la flèche de la grue, par la formule de calcul : $$\mathrm{Ng}=\mathrm{Nc}/\mathrm{R}$$
  
  
  Cependant, dans la mesure où le rapport R est quelconque, il peut s'agir pour lui-même comme pour son inverse 1/R d'un nombre décimal possédant un nombre de décimales infini. Dans ce cas, il faut tronquer donc arrondir ce nombre, c'est-à-dire ne conserver qu'un nombre limité de décimales, pour l'enregistrer et le traiter dans le calculateur. Ceci entraîne une erreur systématique dans la détermination, à partir du nombre de tours du capteur, du nombre de tours effectués par la flèche, donc dans la détermination de la position de la flèche elle-même, et comme on le comprend aisément cette erreur ne pourra qu'augmenter avec le nombre de tours effectués dans un même sens par la flèche.

To then be able to properly exploit the rotation of the sensor such as potentiometer, one of the two following solutions is currently used:

• A first purely mechanical solution consists in inserting for the rotational drive of the sensor an additional set of gearing, of inverse ratio to the ratio R = D / d (crown / gear ratio) previously mentioned. Thus, the angular sensor rotates in perfect synchronism with the boom of the crane, that is to say that the sensor itself describes exactly one full turn, for a complete turn of the boom. In this case, however, the system is specific to each pinion / crown pair and, even if this system introduces no measurement error thanks to the perfect synchronism of rotation between the sensor and the arrow, such a system is certainly not universal considering the existing variety of crowns and gables.
• A second solution, allowing a variety of uses, is to predefine a number of standardized crown / pinion pairs, each pair corresponding to a ratio R = D / d which can be any number. The angular sensor such as potentiometer, the rotation of which is linked to that of the arrow, thus totals a number of revolutions (Nc) of this sensor itself. An integrated calculator, knowing the ratio R of the set of gears (R = D / d is: number of teeth of the crown / number of teeth of the pinion), deduces the number of turns (Ng) made by the arrow of the crane, by the calculation formula: $$\mathrm{ng}=\mathrm{Nc}/\mathrm{R}$$
  
  
  However, since the ratio R is arbitrary, it can be for itself as for its inverse 1 / R of a decimal number having an infinite number of decimals. In this case, it is necessary to truncate so round this number, that is to say, keep only a limited number of decimals, to record and process it in the calculator. This causes a systematic error in the determination, from the number of turns of the sensor, the number of revolutions made by the arrow, so in the determination of the position of the arrow itself, and as it is easy to understand this error can not to increase with the number of turns made in the same direction by the arrow.

Such a systematic error leads to an imprecise indication of the direction of the arrow, with a more or less significant drift compared to the actual position of the arrow, and it can have adverse consequences on the control of the crane and on the safety .

• pour une couronne de 94 dents et un pignon de 12 dents :
  • un écart angulaire de 0,357 degré par tour de la flèche ;
• pour une couronne de 111 dents et un pignon de 12 dents :
  • un écart angulaire de 0,566 degré par tour de la flèche.

By way of example, referring to a POTAIN TOP TRACING notice of the Applicant, edition of 12.03.02, reference 92M-0150-012-0, pages 18 and 19, indicating the choice and mounting of the orientation sensor gears. depending on the type of crown, we can see:

• for a crown of 94 teeth and a pinion of 12 teeth:
  • an angular deviation of 0.357 degrees per revolution of the boom;
• for a crown of 111 teeth and a pinion of 12 teeth:
  • an angular difference of 0.566 degrees per revolution of the arrow.

Thus, the error is by no means negligible, and it may even rise to several degrees, after a small number of turns of the boom of the crane.

The aim of the invention is to avoid this drawback and it is therefore intended to eliminate the systematic error due to the reduction ratio, in order to obtain in all cases a direct and exact indication of the position of the arrow, whatever the number of turns made by this arrow, and especially whatever the number of teeth of the crown. In other words, the object of the invention is to obtain a position indicator which provides an indication of rotation identical to the actual rotation of the boom, however without resorting to the mechanical device described above (under the designation "first solution").

This object is achieved by a position indicator having all the characteristics, in combination, according to claim 1.

For this purpose, it is proposed an indicator of the position in space, that is to say of the orientation, the boom of a crane, including a tower or a boom crane liftable, the indicator being associated with a rotation mechanism of the crane and comprising an angular sensor driven in rotation by means of a pinion having teeth in a fixed number (d), which pinion meshes with a ring gear having number of teeth (D) and belonging to the rotation mechanism of the crane, so that the rotation of the angular sensor is representative of the rotation of the boom of the crane, the indicator also comprising a computer which, from the number of revolutions measured by the angular sensor, determines the number of revolutions made by the arrow, this position indicator being essentially characterized by the fact that the aforementioned pinion has teeth whose number (d) is equal to a power of two (2 ⁿ ), so that the reduction ratio (R) , defined as the quotient of the number of teeth (D) of the crown by the number of teeth (d) of the pinion, a decimal number with a finite number of decimals, regardless of the number of teeth (D) of the crown , this decimal number (R) being introduced to its exact value in the computer, for the determination by the latter of the number of revolutions made by the boom of the crane from the number of revolutions measured by the angular sensor.

Thus, whatever the number of teeth of the crown, the choice for the pinion of a number of teeth which is a power of two (2 ⁿ ), allows to obtain a reduction ratio which is a number with decimals in a finite number, relatively small, and this report can be introduced, without being truncated, in the memory of the processing computer. As a result, the division of the measured number of turns of the sensor by the reduction ratio provides the exact rotation value of the boom of the crane. More precisely, a precisely determined (and not approximately evaluated) number of sensor turns corresponds here to a complete revolution of the boom of the crane. The "scaling" of the information provided by the sensor is thus performed without error.

As a gear having a number of teeth equal to a power of two (2 ⁿ ), one can theoretically consider a pinion with 2, 4, 8, 16, 32, ... teeth. For practical reasons of quality of meshing between the pinion and the crown, and also of size of the device, the number of teeth of the pinion will preferably be chosen equal to sixteen.

For the angular sensor associated with the pinion, it is advantageously an absolute multi-turn encoder, in which case the computer part is preferably integrated in said encoder, the encoder thus providing a signal which directly represents the angular position of the arrow.

• Figure 1 est une vue partielle, en perspective, d'une grue à tour équipée d'un indicateur de position de flèche conforme à la présente invention ;
• Figure 2 est un diagramme simplifié illustrant le fonctionnement de cet indicateur de position.

The invention will be better understood with the aid of the description which follows and the examples given below, with reference to the appended schematic drawing. representing, by way of example, one embodiment of this crane boom position indicator:

• Figure 1 is a partial view, in perspective, of a tower crane equipped with an arrow position indicator according to the present invention;
• Figure 2 is a simplified diagram illustrating the operation of this position indicator.

The figure 1 is a very partial and simplified view of a tower crane (taken here as an example of application), showing the region of its rotation mechanism with a fixed pivot 2 for example secured to the top of the mast of the crane, and a pivot mobile 3 secured to the boom of the crane, the boom is thus made steerable. The rotation mechanism comprises a ring gear 4, fixed by screws 5 on the fixed pivot 2, and motorized means (not shown) which are carried by the mobile pivot 3 and which, by cooperating with the ring gear 4, control the rotation of the boom, this in a manner known per se. The ring 4 has gear teeth 6 in relatively large numbers, of the order of one hundred, the number of teeth 6 of the ring 4 being designated D.

The indicator of the position of the arrow is designated generally by the reference 7. It comprises an angular sensor or rotation sensor 8 such as a multiturn absolute encoder, which is held by a support 9 fixed on the mobile pivot 3 and which is thus placed on the side of the ring gear 4. The inner rotating part of the angular sensor 8 is integral in rotation with a pinion 10 of vertical axis A, which meshes with the ring gear 4. The pinion 10 has teeth 11 whose the number is equal to a power of two (2 ⁿ ), this number being more particularly equal to sixteen (or two power four).

The position indicator 7 of the arrow further comprises a computer, symbolized by a block 12, which receives and processes the signal from the angular sensor 8, and for this purpose stores the reduction ratio R of the gear constituted by the toothed crown 4 and the pinion 10, this ratio being: R = D / d.

Taking into account the choice of the number of teeth d of pinion 10, equal to 2 ⁿ and in particular to 2 ⁴ = 16, and whatever the number of teeth D of crown 4, the reduction ratio R is a number which always has a limited number of decimals.

For example, for a crane having a crown 4 of 113 teeth, if a pinion 10 of thirteen teeth was used, the ratio R would be: $$113/13=8,\mathrm{692\; 307\; 692.}$$

avec un nombre de décimales fini, à savoir quatre décimales dans cet exemple. Ce rapport R peut ainsi être introduit exactement dans le calculateur 12 associé au capteur 8.On the other hand, by choosing according to the invention a pinion 10 of sixteen teeth, the ratio R becomes: $$113/16=7,0625$$

with a finite number of decimal places, ie four decimal places in this example. This ratio R can thus be introduced exactly into the computer 12 associated with the sensor 8.

As another example, corresponding to another type of crane, the crown has 163 teeth and in this case, the pinion 10 always having sixteen teeth, the ratio R becomes: $$163/16=10,1875$$

• Un tour complet de la flèche, c'est-à-dire une variation continue de son angle d'orientation de 0° à 360°, est mesurée par R tours du capteur, R étant le rapport du nombre D des dents de la couronne 4 au nombre d des dents (dans l'exemple considéré : seize dents) du pignon 10.
• Un traitement, réalisé à l'intérieur même du capteur 8 fournit un signal S qui représente directement la position angulaire de la flèche, tel qu'un signal électrique analogique croissant linéairement en fonction de cet angle, par exemple entre une valeur initiale de 4 mA pour un angle de 0° et une valeur finale de 20 mA pour un angle de 360°. Dans le cas d'une rotation de la flèche sur plus d'un tour dans le même sens, le signal revient à sa valeur initiale exactement après chaque tour complet (360°), sans décalage, ceci quel que soit le nombre de tours consécutivement décrits par la flèche.

Always considering this last example, the result indicated means that, every 10,1875 turns of the sensor 8, the boom of the crane will have exactly carried out a complete revolution. As illustrated in the diagram of the figure 2 to convert the number of turns of the sensor 8 into a number of rotations of the arrow, in the case where the sensor is an absolute multi-turn encoder, the "scaling" function of the information is advantageously integrated in this sensor:

• A complete rotation of the arrow, that is to say a continuous variation of its orientation angle from 0 ° to 360 °, is measured by R turns of the sensor, R being the ratio of the number D of the teeth of the crown. 4 to the number of teeth (in the example considered: sixteen teeth) of the pinion 10.
• A processing performed inside the sensor 8 provides a signal S which directly represents the angular position of the arrow, such as an analog electrical signal linearly increasing as a function of this angle, for example between an initial value of 4 mA. for an angle of 0 ° and a final value of 20 mA for an angle of 360 °. In the case of a rotation of the arrow on more than one turn in the same direction, the signal returns to its initial value exactly after each complete turn (360 °), without any shift, whatever the number of turns consecutively described by the arrow.

It is thus understood that the computer 12, shown separated from the sensor 8 for the purposes of the explanation, can in a way be integrated with this sensor 8, thus enabling it to deliver a position signal P which is directly the image of the angle of the arrow.

• par définition même de cette invention, en utilisant une couronne dentée avec un nombre de dents quelconque, du moment que le nombre de dents du pignon est une puissance de deux ;
• en réalisant le capteur angulaire sous toute forme appropriée, analogique ou numérique, tel que potentiomètre ou codeur de tout type, le calculateur de traitement étant intégré à ce capteur ou extérieur à celui-ci ;
• en destinant le même indicateur de position à des grues à tour de tout type, ou encore à des grues à flèche relevable, qui peuvent dans l'un ou l'autre cas être soit des grues avec une flèche montée tournante au sommet d'un mât fixe, soit des grues avec une partie tournante plus importante, incluant non seulement la flèche mais aussi tout ou partie du mât de la grue, auquel cas l'indicateur sera installé au niveau du mécanisme de rotation de cette partie tournante.

One would not depart from the scope of the invention, as defined in the appended claims:

• by definition even of this invention, using a ring gear with any number of teeth, as long as the number of teeth of the pinion is a power of two;
• by producing the angular sensor in any appropriate form, analog or digital, such as potentiometer or encoder of any type, the processing computer being integrated in this sensor or outside thereof;
• by assigning the same position indicator to tower cranes of any type, or to luffing jib cranes, which can in either case be either cranes with a rotating boom at the top of a fixed mast, or cranes with a larger rotating part, including not only the boom but also all or part of the mast of the crane, in which case the indicator will be installed at the rotation mechanism of this rotating part.

Claims (4)

1. An indicator of the position in space, i.e. of the orientation of the jib of a crane, notably of a tower crane or a hoistable jib crane, the indicator (7) being associated with a mechanism of rotation of the crane and comprising an angular sensor (8) driven into rotation via a cog (10) having teeth (11) in a determined number (D), said cog (10) meshes with a toothed crown (4) having teeth (6) in a determined number (D) and belonging to the mechanism for rotating the crane, so that the rotation of the angular sensor (8) is representative of the rotation of the jib of the crane, the indicator (7) also comprising a computer (12) which, from the number of turns measured by the angular sensor (8), determines the number of turns performed by the jib, characterized in that the aforementioned cog (10) has teeth (11), the number of which (d) is equal to a power of two (2ⁿ), so that the reduction ratio (R), defined as the quotient of the number of teeth (D) of the crown (4) by the number of teeth (d) of the cog (10), is a decimal number having a finite number of decimals, regardless of the number of teeth (D) of the crown (4), this decimal number being introduced at its exact value into the computer (12), for determination by the latter of the number of turns performed by the jib of the crane from the number of turns measured by the angular sensor (8).
2. The jib position indicator for a crane according to claim 1, characterized in that the number (d) of teeth (11) of the cog (10) is equal to sixteen.
3. The jib position indicator for a crane according to claim 1 or 2, characterized in that the angular sensor (8) associated with the cog (10) is an absolute multiturn encoder.
4. The jib position indicator for a crane according to claim 3, characterized in that the computer portion (12) is integrated to said encoder, and in that the encoder thus provides a signal (S) which directly represents the angular position of the crane.

Images