EP0003939A2 - Improvements in hydraulically operated lifting devices - Google Patents

Abstract

Hydraulic lifting device comprising two articulated arms actuated by jacks, and means for detecting the pressure of the circuit supplying the hydraulic jacks. The pressure-detector means 21, 23 are arranged so as to lock the arms at 27a, 35a as soon as the moment of the load generates a pressure greater than a predetermined value; furthermore, safety means 31 to 34, 37 to 40, 45 to 48 are provided for checking the movements of the arms, which means are arranged in order to permit, by virtue of means 30, 36 for detecting the angular positions of the arms, the controlling of the arms at 27b, 35b uniquely in a sequence which reduces the moment of the load. Application to auxiliary handling devices. <IMAGE>

Description

The present invention relates to improvements, aimed at increasing safety, made to hydraulically controlled lifting devices comprising two arms hinged to each other and actuated by respective hydraulic cylinders, each arm cannot be raised beyond of the extension of the arm which precedes it, said lifting device comprising, on the one hand, pressure detector means for detecting the pressure of the supply circuit of said hydraulic cylinders, these pressure detector means being arranged to block the arms as soon as that the moment of charging generates a pressure greater than a predetermined value, on the other hand, means for security control of the movement of the arms which are arranged to, first of all, be brought into operational position by said means for detecting pressure and for, ensu-ite, authorize the control of the arms only according to a sequence which decreases the moment of the load and, on the other hand finally, means detect ors of angular position associated with each arm and each arranged to deliver two signals representative of the position of the arm considered situated respectively above and below the horizontal passing through the articulation of said arm.

Hitherto, in lifting devices of the aforementioned kind, the safety systems have been arranged to cause the load to descend when appropriate detector means (for example mechanical or hydraulic) detect a condition corresponding to a moment value. load above which the lifting device could be overturned.

In particular, in the case where the load is moved only by movement of one or more arms with hydraulic control (i.e. without handling the load using a winch), one or both arms were then brought down without the possibility of stopping this movement until one of the arms where the load meets a fulcrum.

This arrangement has many drawbacks, in particular the fact that it is not possible to control the place where the load has descended, which therefore risks being deposited in an undesirable location; this may result in damage to the load, or even the destruction thereof, and in addition accidents may be caused if someone is under the load at the time considered.

In addition, although this safety system is widely used, in particular for auxiliary handling devices (especially those mounted on trucks to allow them to be loaded or unloaded), the operator's loss of control of the lifting device is contrary to the legislation currently in force.

According to patent FR n ° 73 17194 published under the number 2 184 108, there is also known a device of the aforementioned kind in which means are provided so that, when a condition corresponding to a value of the moment of charging is detected beyond which the device risks being overturned, the user can control the movement of the first arm, but only in the direction in which the load moment is reduced.

To this end, the known means comprise a detector of the position of the first arm of the lifting device which selects one or the other of two control circuits of the hydraulic actuating cylinder of the arm depending on whether said arm is respectively above or below the horizontal plane passing through the articulation of said arm to its support. Thanks to this arrangement, the arm can only be raised if it is above the horizontal plane and can only be lowered when it is below the horizontal plane.

However, in this known arrangement, nothing is provided to control the position and movement of the second arm which is articulated at the end of the first arm and which can therefore be freely controlled, whatever its position relative to the first arm, whatever the position of the load, and whatever the position of the first arm, relative to the above-mentioned horizontal plane.

This is a serious shortcoming because controlling the movement of the second arm in an inappropriate direction can counteract the beneficial effect on the safety of the means for controlling the movement of the first arm and such movement in an inappropriate direction can , also further, cause an increase in the load moment despite the control exerted on the first arm.

It will also be noted that it is not enough, to remedy this defect, to associate with the second arm control means similar to those provided for the first arm in the aforementioned known device.

Indeed, if this were so, only the positions of the two arms with respect to horizontal planes passing respectively through the articulations of said arms would be taken into account and certain possibilities of increasing the moment of the load would not be excluded.

Under these conditions, the user would be obliged to carry out himself the selection of the only commands of the arms which would be appropriate to decrease the moment of the load and no security would then be provided, in the device, to prevent those of the commands causing an increase in the timing of the charge and not controlled by the means in place.

However, it should also be taken into account that the handling of certain types of lifting devices of the type envisaged, such as the auxiliary handling equipment mentioned above, is entrusted to relatively unskilled personnel, who in general are none other than drivers of vehicles fitted with said gear, to which only a few rudiments of driving lifting gear have been instilled. They are therefore by no means qualified personnel such as those who are empowered to handle autonomous lifting devices such as cranes or the like.

It would therefore be extremely dangerous to leave the selection of the only maneuvers to be carried out to reduce the moment of charging to the sole free will of the user: even if certain undesirable maneuvers were prevented by known devices, other equally dangerous maneuvers would remain possible due to the incapacity or inattention of the user.

The invention is therefore esse Only intended to overcome the drawbacks of the devices known to date, by providing security means which certainly prevent any increase in the moment of charging, without however requiring an excessive complication of the commands of the lifting device.

• - lorsque les deux bras occupent respectivement des positions situées au-dessus d'une première et d'une seconde horizontales passant respectivement par leurs articulations, les moyens de contrôle de sécurité sont commandés par les moyens détecteurs de position de manière telle qu'ils autorisent le relèvement du premier et/ou du second bras, mais interdisent leur abaissement,
• - lorsque le premier bras occupe une position située au-dessus de la première horizontale et que le second bras occupe une position située au-dessous de la seconde hori- sontale, les moyens de contrôle de sécurité sont commandés par les moyens détecteurs de position de manière telle qu'ils interdisent tout mouvement (relèvement ou abaissement) du premier bras, mais autorisent l'abaissement du second bras en interdisant son relèvement,
• - et, lorsque le premier bras occupe une position située en-dessous de la première horizontale, les moyens de contrôle de sécurité sont commandés par les moyens détecteurs de position de manière telle qu'ils autorisent l'abaissement du premier et/ou du second bras, mais interdisent leur relèvement.

In accordance with the invention,

• - when the two arms respectively occupy positions located above a first and a second horizontal passing respectively through their articulations, the safety control means are controlled by the position detector means in such a way that they allow raising the first and / or second arms, but prohibiting their lowering,
• - when the first arm occupies a position situated above the first horizontal and the second arm occupies a position situated below the horizontal second, the safety control means are controlled by the position detecting means of in such a way that they prohibit any movement (raising or lowering) of the first arm, but authorize the lowering of the second arm by prohibiting its raising,
• - And, when the first arm occupies a position located below the first horizontal, the safety control means are controlled by the position detector means in such a way that they allow the lowering of the first and / or the second arms, but prohibit their raising.

Preferably, when the second arm is provided with at least one hydraulic extension, the safety control means are arranged to authorize the movement of the extension only in the direction of its retraction and prohibit its movement in the direction of his exit.

In addition, when the lifting device is equipped with a load lifting winch, the pressure detecting means controls the control of the winch so that, when said means detect a pressure higher than a determined pressure, they prevent the lifting of a load from its rest plane.

When the last arm or the last hydraulic extension can be extended using at least one mechanical extension, the pressure detector means comprise at least two pressure sensors each of which is calibrated for a predetermined number of extensions (counted from 0 when no extension is used), first selection means being provided for automatically selecting the appropriate pressure sensor as a function of the number of mechanical extensions extended.

In a preferred embodiment of the invention, the safety control means are made up of limit switches associated with the control distributors for actuating jacks of the arm (s) and / or hydraulic extensions and / or the winch and that said switches are inserted into electrical supply circuits for solenoid valves for controlling said jacks, second selection means, controlled by the angular position detector means, selecting the appropriate switches to allow the sole movement of the or arms decreasing the moment of charge.

In addition, it is desirable that detection means are provided to detect the coming into abutment of the arm or of all the arms in the maximum high position - coming into abutment causing an overpressure of the supply circuit of at least one hydraulic cylinder, which causes the safety means to be put into operational position by means of pressure sensors and therefore blocking of the arm or of all of the arms and the impossibility of lowering it or these - and to authorize, from said maximum high position and despite the operational positioning of the means safety, lowering, over a very short distance, of the arm or arms.

Through one or the other or any combination of the foregoing, while being assured of stopping a movement of one and / or the other arm ₂ capable of imparting to the load movement such that the lifting device can tilt, it is also guaranteed to be able to continue to maneuver the load but only under certain conditions which do not affect safety. Furthermore, this authorization to continue the maneuvers and the selection of the only authorized maneuvers is not; left to the sole initiative of the user: on the contrary, they are determined entirely automatically and any manipulation of the arm control members to cause movement of the arms in a direction incompatible with safety remains ineffective.

In this way, a user not specialized in the handling of lifting devices, as is often the case with regard to auxiliary handling devices placed on board trucks, can in no case carry out false maneuvers likely to cause the lifting device and its support to overturn.

In addition to the main provisions which have just been stated, the invention also provides for a certain number of additional provisions which aim to further increase safety and which are preferably used in combination with the main provisions because it is in this case that they seem to be of the greatest interest.

A first additional provision which applies when the lifting device, or more usually the support of the lifting device, is equipped with at least two lateral stabilizing jacks for supporting the ground; it is therefore important that at least one of these jacks is actually in contact with the ground in order to prevent the lifting device from overturning when the arm or the arm assembly is made to rotate about a vertical axis. by supporting a load.

Provision is then made for the lifting device to comprise means for detecting the support on the ground stabilizing jacks associated functionally with the safety control means for blocking the arm or arms when at least one jack is not in support. on the ground or else, in the case where a single stabilizing cylinder is in contact with the ground and where the arm or arms are displaced in horizontal rotation, when the center of gravity of the assembly reaches a limit of the support polygon.

Furthermore, it is important that the lifting device is placed in a suitable predetermined position (in particular with respect to a horizontal plane) so as to avoid it overturning when the arm or arms are subjected to a horizontal rotational movement by supporting a charge.

To avoid the risk of overturning under these conditions, a second additional provision of the invention consists in making the lifting device comprise attitude detector means functionally associated with the safety control means to block the arm (s) to allow movement of the arm (s) only if the lifting device is in a suitable predetermined position.

Under certain conditions of use of the lifting device, it can be dangerous for the arm (s) to be turned, around a vertical axis, beyond a certain position: the arm (s) must not be turned only in a specific angular sector, for example, the lifting device being placed on the platform of a truck, to prevent the end of the arm or the load from hitting the driver's cab.

To avoid this risk, provision is made, according to a third additional provision, to have the ap similar lifting of the rotation limitation means to limit the horizontal rotation of the arm (s) in a predetermined angular sector.

Finally, the standards and specifications stipulate, as a safety measure, the obligation that the lifting devices must be able to withstand certain overloads. It is therefore necessary to subject lifting devices to such overloads during tests.

However, by construction principle itself, the application of an overload normally causes the safety system to be put in the operational position and the blocking of the arm (s) of the lifting device, thus making any overload test impossible.

To allow, despite everything, such tests by authorized persons, a fourth additional provision consists in making the lifting device comprise a shunt device arranged, so that when it is actuated, bypass the safety system and allow operation. of the lifting device under conditions normally causing said safety system to be brought into operational position, the shunt device being further arranged so that its actuation permanently destroys an element of the lifting device, said item not accessible to an unauthorized person.

• - la figure 1 est un schéma synoptique illustrant le fonctionnement général de sécurité d'un appareil de levage muni d'un bras unique ;
• - la figure 2 est un schéma synoptique illustrant de façon plus détaillée le fonctionnement de sécurité d'un appareil de levage muni d'un seul bras et de prolongations ;
• - la figure 3 est un schéma synoptique illustrant de façon plus détaillée le fonctionnement de sécurité d'un appareil de levage muni de deux bras et de prolongations ;
• - la figure 4 est un schéma des différentes positions susceptibles d'être occupées par les deux bras de l'appareil de levage concerné par la figure 3 ;
• - la figure 5 est un exemple de réalisation d'un dispositif de commande d'un appareil de levage fonctionnant comme indiqué sur la figure 3 ;
• - la figure 6 est un schéma synoptique illustrant le fonctionnement général de sécurité d'un appareil de levage muni d'un certain nombre de dispositions complémentaires conformes à l'invention ;
• - la figure 7 est un exemple de réalisation d'une partie d'un dispositif de commande d'un appareil de levage du genre de celui de la figure 5 comportant un certain nombre des dispositions schématisées à la figure 6 ;
• - et la figure 8 est un exemple de réalisation des autres dispositions de la figure 6, destiné à être associé à la partie représentée à la figure 7.

The invention will be better understood with the aid of the following description of some of its embodiments, given by way of illustrative examples, without limiting characters. In this description, reference is made to the appended drawings in which:

• - Figure 1 is a block diagram illustrating the general safety operation of a lifting device provided with a single arm;
• - Figure 2 is a block diagram illustrating in more detail the safety operation of a lifting device provided with a single arm and extensions;
• - Figure 3 is a block diagram illustrating in more detail the safety operation of a lifting device with two arms and extensions;
• - Figure 4 is a diagram of the different positions that may be occupied by the two arms of the lifting device concerned by Figure 3;
• - Figure 5 is an exemplary embodiment of a control device of a lifting device operating as shown in Figure 3;
• - Figure 6 is a block diagram illustrating the general safety operation of a lifting device provided with a number of additional arrangements according to the invention;
• - Figure 7 is an embodiment of part of a control device of a lifting device of the kind of that of Figure 5 comprising a number of the arrangements shown schematically in Figure 6;
• FIG. 8 is an example of an embodiment of the other provisions of FIG. 6, intended to be associated with the part shown in FIG. 7.

Referring to Figure 1, we will first describe the general operation.du security system of a lifting device, considering the case where said lifting device is only equipped with a single arm whose movement in rotation is controlled by a hydraulic cylinder.

A value of the moment of the load corresponds to a value of the pressure of the hydraulic fluid in the supply circuit 1 of the control cylinder of the arm. This pressure is detected by pressure detector means 2.

When the pressure of the hydraulic fluid reaches a predetermined value corresponding to a moment of the load slightly less than the moment of overturning of the lifting device, the pressure detecting means 2 cause the closure at 3 of a member 4 for controlling the the flow of hydraulic fluid and the arm remains blocked in the position it occupies at this time.

At the same time as the closure of the member 4, the pressure detector means 2 put into operation or switch on means 5 for detecting the angular position of the arm. These select, depending on the angular position in which the arm is locked, the or a sequence of displacement 6 which it is possible to make the arm follow to cause a decrease in the moment of the load and the opening of the 'control member 4 is obtained in 7, with priority over the closure controlled in 3 by the pressure detector means 2, to authorize the movement of the arm according to the required sequence.

Thanks to this arrangement, whatever the maneuvers controlled by the operator, only a maneuver will be authorized and may actually be carried out during which the movement of the arm reduces the moment of the load.

Referring now to FIG. 2, a description will be given of the operation of the safety system of a lifting device equipped with a single arm movable in rotation in a vertical plane, this arm being provided with an extension with hydraulic control and two manually operated extensions.

By hydraulically controlled extension is meant an extension element, generally sliding inside, inside the beam constituting the arm which carries it, retractable in said arm and capable of occupying a fully or partially extended position under the action of hydraulic control means (for example a cylinder). In the following description, this element will be designated by the expression "hydraulic extension".

Similarly, manually operated extension means an extension element, generally sliding inside the beam constituting the arm which carries it, retractable in said arm and capable of occupying only a fully retracted position or a fully extended position, the transition from one to the other is done manually. In the following description, this element will be designated by the expression "manual extension".

In the case envisaged in FIG. 2, the lifting device is therefore provided with a retractable hydraulic extension in the arm, a first retractable manual extension in the hydraulic extension and a second retractable manual extension in the first manual extension.

Because the manual extensions can only be retracted or extended, without being able to occupy intermediate positions, there are three values of the moment of the load capable of causing the lifting device to overturn; these three values correspond respectively to the use of the arm and the hydraulic extension alone with the two manual extensions retracted, to the use of the arm and of the hydraulic extension with the first manual extension extended, and finally to the use of the arm and of the hydraulic extension with the two manual extensions extended.

It is therefore necessary that the means for detecting the pressure of the hydraulic fluid in the supply circuit of the control cylinder of the arm can detect three different maximum values of the pressure corresponding respectively to the three cases above. It is then preferable, to simplify the design of the device, to provide three pressure sensors respectively tared accordingly.

To this end, the first case under consideration is detected in 20 (arm and hydraulic extension only) with selection of a first pressure sensor 24; the output of the first manual extension is detected at 22 with selection of a second pressure sensor 23; finally, at 24, the output of the second manual extension is detected (the first then also being output as indicated above) with selection of a third pressure sensor 25.

The pressure of the hydraulic fluid in the supply circuit 26 of the control cylinder of the arm is applied to each sensor 21, 23 and 25.

When the pressure reaches a predetermined value for which the sensor selected is calibrated according to the configuration of the boom of the lifting device, the sensor considered causes the closure at 27a and 28a of the control members 27 and 28 of the food hydraulic arm actuating cylinders and hydraulic extension respectively.

The arm and the hydraulic extension are then locked in the position they occupied at the time.

Any additional extension of the boom resulting in an increase in the load moment, it is then possible to authorize a displacement of the hydraulic extension, but only in the direction of reentry.

To this end, at the same time as the closing of the members 27 and 28, a circuit 29 is put into operation which inhibits the control of the output of the hydraulic extension and which only authorizes the control of its reentry. If the re-entry of the hydraulic extension is controlled, the control member 28 is then opened at 28b with priority over closure 28a, to cause the hydraulic supply to the corresponding cylinder.

In the same way, the arm can undergo a rotation in a determined direction, making it possible to decrease the moment of the load, according to its position relative to the horizontal. If the arm is blocked above the horizontal, its descent would have the effect of increasing the moment of the load, but on the other hand its rise will cause a decrease in said moment. Conversely, if the arm is blocked below the horizontal, its rise would increase the moment of the load while its descent will decrease this moment.

Therefore, always at the same time as the closure of the members 27 and 28, a device 30 for detecting the angular position of the arm is put into operation.

If the arm is located above the horizontal (that is to say makes an angle greater than 90 ° with the vertical), the output 30a of the device 30 'triggers at 31 the inhibition of the descent command of the arm and on the other hand authorizes the control of the raising of the arm. Therefore, when carried out, the command to raise the arm at 33 causes the opening 27b, with priority over the closure 27a, of the member 27 to feed the cylinder, the latter acts on the arm to do so ascend.

If, on the other hand, the arm is located below the horizontal (that is to say makes an angle of less than 90 ° with the vertical), the output 30b of the device 30 triggers at 32 the inhibition of the command of rise of the arm and authorizes the control of the descent of the arm. Thus, when carried out, the lowering command of the arm at 34 causes the opening at 27b, with priority over closure 27a, of the member 27 to feed the cylinder, which acts on the arm to make it descend.

Of course, the reduction in the moment of the load can be obtained by acting either on the arm, or on the hydraulic extension, or even on both simultaneously.

Referring to Figures 3 and 4, we will now describe the operation of the safety system fitted to a lifting device with two arms, a hydraulic extension and two manual extensions.

As shown schematically in Figure 4, the arm 41 (hereinafter referred to as "first arm") is articulated in rotation in a vertical plane at the upper end of a barrel 43, substantially vertical, resting on a support 44 (by example part of a truck chassis.). At the free end of the arm 41 is articulated in rotation in a vertical plane an arm 42 (hereinafter referred to as "second arm") which carries the hydraulic extension and the manual extensions as explained previously (in FIG. 4, the hydraulic extension and manual extensions are not shown).

In such a lifting device, the reduction in the moment of the load depends on the position of the load with respect to the respective horizontals of the two arms 41 and 42, that is to say with respect to the horizontal H passing through l articulation of the arm 41 to the barrel 43 and to the horizontal H ₂ passing through the articulation of the arm 42 to the arm 41.

FIG. 4 shows different possible configurations (designated by the letters A to D) of the boom of the lifting device as a function of the relative position of the arms.

It will also be assumed, as is the current case, that the arm 42 cannot be raised beyond the alignment with the arm 41.

In configuration A, the arm 41 is located below the horizontal H ₁ and the arm 42 is also located below the horizontal HA2: therefore the end of the arm 42 is located below the horizontal H ₁ and ^H _A 2 ^.

Lowering the arm 41 and / or the arm 42 has the effect of reducing the moment of the load, while raising the arm 41 and / or the arm 42 increases this moment.

In configuration B, the arm 41 is located above the horizontal H ₁ and the arm 42 is also located above the horizontal H _B2 : the end of the arm ₄₂ is located above the horizontal H ₁ and H _B2 .

The raising of the arm 41 and / or of the arm 42 decreases the moment of the load while the lowering of the arm 41 and / or of the arm 42 increases this moment.

In the configurations C and .D, the arm 41 is located above the horizontal H ₁ , while the arm 42 is located below the respective horizontal H _C2 and ^H D2.

In configuration C, the end of the arm 42 is located between the horizontal H ₁ and HC2: in this case, the reduction in the moment of the load can be obtained by raising the arm 41 and / or by lowering the arm 42.

On the other hand, in configuration D, the end of the arm 42 is located below the horizontal H ₁ : thus, the reduction in the moment of the load can be obtained by lowering the arm 41 and / or the arm 42, therefore in the same sequence as in configuration A.

Therefore, the decrease in the moment of the load is obtained, in the same way as in the case of a device with a single arm, by detection of the position of the first arm 41, except in the case where the end of the arm 42 is located between the two horizontal H ₁ and H _C2 , the arm 41 then having to be lowered contrary to what was provided for the device with only one arm.

In Figure 3, there is shown in block diagram the safety operation of the lifting device provided with two arms. The same reference numerals designate the elements or functions identical to those of FIG. 2. This diagram is substantially similar to that of FIG. 2, with however the addition of a hydraulic control member 35 of the second arm and the addition of a second permissive circuit for actuating the second arm as a function of its angular position.

Therefore, the locking of the arms and hydraulic extension of the device are carried out in the same manner as described above, by closing at 27a, 28a, and 35a of the members 27, 28 and 35, respectively, for controlling the hydraulic supply of the actuating cylinders of the first arm, of the extension and of the second arm, respectively.

Similarly, the authorization to re-enter the hydraulic extension and the inhibition of its exit is provided by circuit 29.

By cons, to the device 30 for detecting the angular position of the first arm relative to the horizontal is associated a second device 36 detecting the angular position of the second arm relative to the horizontal passing through its articulation.

In view of what has been described above with regard to FIG. 4, the indications provided by the outputs of the two devices 30 and 36 are compared to allow the possible sequence or sequences to reduce the moment of charging and inhibit the commands resulting in an increase in said moment.

Thus, when the second arm is located above the horizontal passing through its articulation to the first arm, the output 36a of the detector device 36 authorizes in 37 the raising of the second arm, but inhibits the control of its lowering.

Therefore, the command at 38 for raising the second arm causes the opening at 35b, with priority on the closure 35a, of the member 35 controlling the supply of the cylinder, which acts on the second arm to raise it.

On the other hand, when the second arm is located below the horizontal passing through its articulation to the first arm, the output 36b of the detector device 36 authorizes at 39 the lowering of the second arm, but inhibits the control of its raising. Therefore the command in 39 for the lowering of the second arm causes the opening at 35b, with priority over closure 35a, of the member 35 controlling the supply of the cylinder, which acts on the second arm to lower it .

With regard now to the control of the first arm, taking into account the incompatibilities mentioned above, it is necessary, in order not to overly complicate the control of the lifting device, that, in the configurations C and D of the figure 4, only the second arm could be lowered, the first arm remaining blocked even if the operator ordered its raising in configuration C or its lowering in configuration D.

Under these conditions, the control of the first arm requires the comparison of the indications of the respective angular positions of the first and second arms.

In the case, detected by an AND function 45, where the two arms are situated above their respective horizontal lines, the raising of the first arm is authorized at 31, but the command for its lowering is inhibited; as indicated previously for FIG. 2, the command at 33 for raising the first arm causes the opening 27b of the member 27 for controlling the supply of the cylinder, which acts on the first arm to raise it.

Likewise, in the case, detected by the AND function 46, where the two arms are located below their respective horizontal lines, the lowering of the first arm is authorized at 32, but the command to raise it is inhibited; thus the command in 34 to lower the first arm causes the opening 27b of the member 27 for controlling the supply of the cylinder, which acts on the first arm to lower it.

On the other hand, in the case, detected by the ET 47 function, where the first arm is above the horizontal and where the second arm is below the horizontal passing through its articulation to the first arm, ( configuration C or D in FIG. 4), the inhibition of the movement control (lowering and raising) of the first arm is obtained at 48, with therefore confirmation of the closure at 27a of the member 27 for controlling the hydraulic circuit d supply to the actuating cylinder of the first arm.

As in the case of a device with only one arm, it is possible to control, when possible, the _: appropriate displacement of the first arm and / or the appropriate displacement of the second arm and / or the retraction of the hydraulic extension .

Referring to Figure 5, we will now describe an embodiment of the control of a hydraulic lifting device provided with two arms, a hydraulic extension and two manual extensions, this device operating as just be described with reference to Figures 3 and 4.

In FIG. 5, the respective control cylinders of the first arm, of the second arm and of the hydraulic extension have been designated by the reference numerals 51, 52 and 53. These cylinders are connected by hydraulic circuits, via respective solenoid valves 54, 55 and 56, to hydraulic distributors 57, 58 and 59 respectively, at three positions, these distributors themselves being connected in parallel with a side to a hydraulic pump 60 and on the other side to the tarpaulin.

• - à la sortie du piston du cylindre correspondant (relèvement du bras ou sortie de l'extension hydraulique) ;
• - au blocage du piston (blocage du bras ou de l'extension) ;
• - et à la rentrée du piston du cylindre correspondant (abaissement du bras ou rentrée de l'extension hydraulique).

In a conventional manner, the three positions of each distributor correspond, from top to bottom in FIG. 5:

• - at the exit of the piston from the corresponding cylinder (raising of the arm or exit of the hydraulic extension);
• - blocking of the piston (blocking of the arm or extension);
• - and when the corresponding cylinder piston retracts (lowering the arm or retracting the hydraulic extension).

In addition, in the hydraulic supply circuit of the cylinder 51 for controlling the first arm, three pressure sensors 61, 62 and 63 are arranged in parallel. These three sensors are calibrated to detect three predetermined values of the fluid pressure. hydraulic in the cylinder circuit of the first arm, these three values corresponding to an excessive moment of the load respectively when the two manual extensions are extended, when the first manual extension is extended and when the two manual extensions are retracted (case shown on the figure 5).

The electrical control circuit of the hydraulic assembly is as follows.

Note first of all that all the relays used are of the open contact type at rest to cause, for safety reasons, the blocking of the device in the event of a failure of one of the relays.

Two limit switches 64 and 65 are respectively associated with the first and second manual extensions and are normally closed when the corresponding extension is retracted.

One of the terminals of the switch 64 is connected to the positive pole of electrical supply and the other terminal is connected to a contact terminal of a relay 66, the other terminal of which is connected to ground through the coil. a relay 67 with two contacts 67a and 67b: the terminals of contact 67a are respectively connected to the positive pole of electrical supply and to one of the terminals of a switch 68 controlled by the pressure sensor 63; the terminals of contact 67b are respectively joined to one of the terminals of a switch 69 controlled by the pressure sensor 62 and to the positive pole of electrical supply. It will be noted that one of the contacts (for example 67b) is open when the other (for example 67a) is closed.

• - d'une part, à l'autre borne de l'interrupteur 68 commandé par le capteur de pression 63,
• - d'autre part, à une borne d'un interrupteur 71 commandé par le capteur de pression 61,
• - et, enfin à la masse à travers la bobine d'un relais 72 à deux contacts.

Likewise, one of the terminals of the switch 65 is connected to the positive pole of electrical supply while the other terminal is connected to the ground, on the one hand, through the coil of the relay 66 and, on the other hand , through the coil of a relay 70 with two contacts 70a and 70b. One of the terminals of the contact 70a is connected to the other terminal of the switch 69 controlled by the pressure sensor 62 while the other terminal of the contact 70a is connected:

• on the one hand, to the other terminal of the switch 68 controlled by the pressure sensor 63,
• on the other hand, to a terminal of a switch 71 controlled by the pressure sensor 61,
• - And, finally to ground through the coil of a relay 72 with two contacts.

The other contact 70b of the relay 70 _of one of its terminals joined to the positive pole of electrical supply and its other terminal joined to the other terminal of the switch 71 controlled by the pressure sensor 61.

One of the contacts 70a, 70b is closed when the other is open.

Finally, with regard to the two contacts 72a, 72b of the relay 72, two respective terminals of these contacts are joined to the two terminals of the contacts 67a, 67b of the relay 67 connected to the positive pole of electrical supply.

The other terminal of the contact 72a is connected, through an indicator light 73, for signaling normal operation, to the anodes of three non-return diodes 74, 75, 76 whose cathodes are respectively connected to the solenoid valves 54, 55 and 56.

It will be noted that the three switches 68, 69 and 71 are normally closed, when the hydraulic pressure is lower than the setting pressure of the pressure sensors which control them.

The electrical circuit which has just been described constitutes a circuit for automatic selection of the appropriate pressure sensor as a function of the position (retracted or extended) of the manual extensions and for controlling the solenoid valves 54 to 56 in normal operation.

We will now describe the system for controlling the lifting device according to a pre-established sequence in the event of overload.

The other half of the contact 72b of the relay 72 is connected, through an indicator light 77 for signaling overload, to a torne of a limit switch 75, tooth the other half is connected to the cathode of the diode 76.

The limit switch 78 is associated with the hydraulic distributor 59 for controlling the cylinder 53 of the hydraulic extension. Like all the limit switches which will be mentioned later, the switch 78 is normally open and is closed only when the distributor 59 is moved (upwards in FIG. 5) to control the retraction of the piston of the cylinder 53 (retraction of the hydraulic extension).

A first detector 79 of the angular position of the first arm is connected to ground and to the positive pole of the power supply and its output is connected to ground through the coil of a relay 80 with two contacts 80a and 80b, of which l one is open when the other is closed.

Each of the two contacts 80a and 80b has a terminal connected to the positive pole of electrical supply.

The other terminal of contact 8Da is connected to a terminal of a limit switch 81 whose other terminal is connected to the cathode of diode 74 associated with the solenoid valve 54. The limit switch 81 is associated with the hydraulic distributor 57 and is closed when the latter is actuated (upwards in FIG. 5) to control the retraction of the piston into the cylinder 51 (lowering of the first arm).

The other terminal of the contact 80b is connected to a terminal of a limit switch 82. This switch 82 is associated with the hydraulic distributor 57 and is closed when the latter is actuated (downwards in FIG. 5) to control the output of the piston from cylinder 51 (raising of the first arm).

The other terminal of the switch 82 is connected to a contact terminal of a relay 83, the other terminal of which is connected to the cathode of the diode 74.

A second detector 84 of the angular position of the second arm is connected to ground and to the positive pole of electrical supply. Its output is connected to ground through the coil of a relay85 with two contacts 85a and 85b, one of which is open when the other is closed.

Each contact 85a, 85b has a terminal joined to the positive pole of electrical supply.

The other terminal of the contact 85a is connected, on the one hand, to the ground via the coil of the relay 83 and, on the other hand, to a terminal of a limit switch 86 whose another terminal is connected to the cathode of the diode 75 associated with the solenoid valve 55. The limit switch 86 is associated with the distributor 58 for controlling the cylinder 52 for actuating the second arm and it is closed when the distributor 58 is moved (down in Figure 5) to control the output of the cylinder piston 52 (raising the second arm).

The other terminal of contact 85b of relay 85 is connected to a terminal of a limit switch 87, the other terminal of which is connected to the cathode of diode 75 associated with the solenoid valve 55. The end switch stroke 87 is associated with the hydraulic distributor 58 and it is closed when the latter is actuated (upwards in FIG. 5) to control the retraction of the piston of the cylinder 52 (lowering of the second arm).

For safety reasons, all relays are preferably (as shown in Figure 5) with closed contact when the coil is energized, so that an anomaly in a relay ² causes the electrical supply to the solenoid valves 54 to 56 to be cut and the arms and the hydraulic extension to be blocked.

The angular position detectors 79 and 84 are preferably proximity detectors indicating the position of the corresponding arm relative to the vertical. The detector 79 is mounted on the first arm and may have for reference the barrel of the lifting device, this barrel being substantially vertical. As for the detector 34. it is fixed to the second arm so as to hang freely.

The operation of the circuits of Figure 5 is as follows.

As regards first of all the selection circuit of the appropriate pressure sensor, it will first be assumed that the two manual extensions are retracted. This is the case shown in FIG. 5 and all the switches and relays are therefore in the positions shown.

As indicated above, the two switches 64 and 65 are closed; therefore, the coil of the relay s 66 being supplied the contact of the relay 66 is closed, and, the relay 67 being energized, its contact 67a is closed. Likewise, the relay 70 is energized and its contact 70a is closed.

Under these conditions, the coil of the relay 72 is connected to the positive power supply pole via the closed contact of the switch 68 and the closed contact 67a of the relay 67.

On the other hand, as the contact 7Gb of the relay 70 is open, the electrical circuit passing through the switch 71 and the coil of the relay 72 is not closed.

Similarly, as the contact 67b of the relay 67 is open, the electrical circuit passing through the switch 69, the closed contact 70a and the coil of the relay 72 is also not closed.

Under these conditions, the two sensors 61 and 62 are electrically off-circuit and only the sensor 63 is included in the electrical circuit for controlling the relay 72, when no manual extension cable is out.

If the first manual extension is now out, the limit switch ₆₄ is open and, the relay 67 being no longer energized, the contact 67a is open and the contact 67b is closed, all other things being equal.

Under these conditions, the electrical circuit, passing through contact 67b, switch 69, contact 70a and the coil of relay 72, is closed.

On the other hand, the contact 70b being open, the circuit passing through the switch 71 and the coil 72 is not closed.

Similarly, the contact 67a being open, the circuit passing through the switch 63 and the coil of the relay 72 is not closed.

Therefore only the pressure sensor 62 is included in the electrical excitation circuit of the relay 72. when the first mechanical extension is out.

If finally the second mechanical extension is also out, the limit switch 65 is also open and, the relay 70 being no longer energized, the contact 70a is open and the contact 70b is closed.

Under these conditions, the electrical circuit including the contact 70b, the switch 71 and the coil 72 is closed.

On the other hand, the contact 70a being open, the electrical circuit passing through the contact 67b, the switch 69 the contact 70a and the coil 72 is not closed.

Likewise, the contact 67a being open, the electrical circuit passing through the switch 68 and the coil 72 is not closed.

So only the pressure sensor 61 is included in the electrical excitation circuit of the relay 72 when the two manual extensions are out.

As a result, whatever the position (retracted or extended) of the manual extensions, only the sensor of appropriate pressure is included in the electrical circuit of excitation of the coil of relay 72.

As long as the lifting device is not subjected to an overload, no overpressure is detected by the pressure sensor in circuit and, the relay 72 being energized, the contact 72b is open and the contact 72a is closed; the solenoid valves 54, 55 and 56 are therefore normally open, and the control of the two arms and of the hydraulic extension can normally be carried out by acting on the hydraulic distributors 57, 58 and 59.

But as soon as the supply pressure of the cylinder 51 for controlling the first arm reaches the setting value of that of the pressure sensors which is connected in the electrical circuit, the sensor causes the opening of its associated switch and the de-energization of the relay 72. Therefore the contact 72a of the relay 72 opens, which causes the closing of the solenoid valves 54 to 56 and the blocking of the arms and of the hydraulic extension in the position they occupied. For its part, the indicator 73 for normal operation has gone out.

Simultaneously, the contact 72b of the relay 72 is closed and the positive supply voltage is brought to the. corresponding terminal of the limit switch 78.

If the valve 59 (down) is actuated in the direction of arrow 88 (corresponding in FIG. 5 to the outlet of the hydraulic extension), the fluid does not circulate since the solenoid valve is closed, being not electrically powered neither by contact 72a nor by switch 78 which are open.

On the other hand, if the distributor 59 is actuated upwards in the direction of the arrow 89 (corresponding in FIG. 5 to the reentry of the hydraulic extension), the distributor causes the switch 78 to close and the solenoid valve s 'opens: the cylinder 53 controls the retraction of the extension.

Furthermore, when the first arm is located below the horizontal, the second arm, as indicated above, is also located below the horizontal passing through its articulation to the first arm (configuration A in FIG. 4).

As a result, the two angular position detectors 79 and 84 do not deliver any output signal and the relays 80 and 85, not being energized, are in the rest position shown in FIG. 5: contacts 80a and 85b closed, contacts 80b and 85a open.

Consequently, if the distributor 57 is actuated in the direction indicated by the arrow 90 (Upwards in FIG. 5) the limit switch 81 is closed rt the positive voltage of electric supply is applied to the solenoid valve 54, ordering its opening. Therefore, the fluid circulates in the cylinder 51 causing the retraction of its piston, therefore the lowering of the first arm.

On the other hand, if the distributor 57 is actuated in the direction of the arrow 91 (downwards in FIG. 5), the limit switch 82 is certainly closed, as the contact 80b of the relay 80 is open, the positive voltage of electrical supply does not reach the solenoid valve 54 which remains closed: the first arm therefore remains blocked.

Similarly, if the distributor 58 is actuated in the direction of the arrow 92 (upwards in FIG. 5), the limit switch 87 is closed and, the contact 85b of the relay 85 being closed, the positive voltage of electrical supply is applied to the solenoid valve 55 which opens: the piston enters the cylinder 52, causing the lowering of the second arm.

On the other hand, if the distributor 58 is actuated in the direction of the arrow 93 (downwards in FIG. 5), the limit switch 86 is certainly closed; but, the contact 85a of the relay 85 being open, the solenoid valve is not energized and remains closed: the second arm remains locked in its position.

When the two arms are located above their respective horizontal lines (configuration B in FIG. 4), the two angular position detectors 79 and 84 deliver an output signal and the two relays 80 and 85 are energized. the contacts 80b and 85a are then open and the contacts 80a and 85b are closed.

Therefore, if the distributor 57 is actuated in the direction of the arrow 90 (upwards in FIG. 5), the limit switch 81 is certainly closed, but, the contact 80a being open, the solenoid valve 54 is not excited and remains closed: the first arm remains blocked.

On the other hand, if the distributor 57 is actuated in the direction of the arrow 91 (downwards in FIG. 5), the limit switch 82 is closed; similarly, the contact of relay 83 is closed since, the contact 85a of relay 85 being closed, its coil is energized; the contact 80b of the relay 80 also being closed, the solenoid valve 54 is energized and opens: the circulating fluid brings out the piston from the cylinder 51 and the first arm rises.

Similarly, if the distributor 58 is actuated in the direction of the arrow 92, the limit switch 87 is certainly closed; but, the contact 85b of the relay 85 being open, the solenoid valve 55 is not energized and does not open: the second arm therefore remains blocked.

On the other hand, if the distributor 58 is actuated in the direction of the arrow 93, the limit switch 86 is closed and, as the contact 85a of the relay 85 is closed, the positive voltage of electrical supply is applied to the solenoid valve 55 which opens: the fluid circulates in the cylinder 52 by causing the piston to exit; so the second arm goes up.

When the first arm is located above the horizontal and the second arm is located below the horizontal which passes through its axis of articulation to the first, the detector 79 delivers a signal exciting the relay 80 while the detector 84 does not deliver a signal and the relay 85 is not energized: therefore, the contacts 80b and 85b are closed while the contacts 80a and 85a are open.

The command of the second macaw is the same as that described above, that is to say that only the lowering of the second arm is authorized, its raising is not possible.

With regard to the first arm, it will be noted that, the contact 85a of the relay 85 being open, the relay 83 is not energized and its contact is open. Therefore, when the distributor 57 is actuated in the direction of the arrow 91, the limit switch is certainly closed, but the supply of the solenoid valve 54 is not ensured due to the opening of the contact 83.

In addition, as indicated above, the solenoid valve 54 is not energized either when the distributor 57 is actuated in the direction of the arrow 90 since the contact 80a of the relay 80 is open.

Therefore, whatever the actuation of the dispenser 57, the first arm remains blocked.

Of course, as follows from the rest of the diagram in FIG. 5, it is possible to simultaneously control the authorized movement of the first arm and / or of the second arm and / or of the hydraulic extension.

Thanks to the security control system which has just been described, it is possible, once the apparatus has been removed. lifting blocked due to overload, carry out certain maneuvers by short-circuiting the blocking command only, if, during the maneuver (s) envisaged, the moment of charging decreases.

The operator therefore retains control of the device, regardless of the configuration of the arms at the time when the overload appeared.

In the case where the load is moved using a lifting winch provided in a lifting device with hydraulic control such as that of FIG. 5, it is advantageous that the pressure detecting means also control the control circuits of the winch, in such a way that, when a pressure higher than a determined pressure is detected, the winch is blocked and the load cannot be lifted from its plane of rest.

In addition, in accordance with the invention, provision is made to supplement the security device which has just been described by a certain number of provisions aimed at increasing security when, in addition to the cases of overload, certain other conditions are not satisfied. during the operation or the start-up of the lifting device.

In FIG. 6, which corresponds to the basic diagram of FIG. 1, these complementary arrangements have been represented while keeping the same reference numerals to designate the elements identical to those of FIG. 1.

In the case where the lifting device is disposed on a support, in particular a mobile support such as for example a vehicle chassis, provision is usually made to equip said support (respectively said truck): retractable beams arranged laterally, on the side and on the other side of the support, and carrying stabilizing cylinders for supporting the ground so as to increase the surface of the support overvoltage polygon, therefore to increase the stability of the assembly, and finally to increase the weight of the loads that can be handled using the lifting device and / or the maximum useful length of the arm or the arm assembly thereof.

As the maximum loads and / or the maximum length of the arm (s) are in this case calculated taking into account these additional supports, the absence of these latter is likely to be the cause of the overturning of the assembly during operation.

However, if these additional supports are normally provided on both sides of the lifting device support, the absence of support on only one side of the support (involuntary or mandatory for example due to the lack of space for removing the second press) does not detract from the operational safety of the lifting device, provided that the lifting device is not brought to the side where the additional support has not come out.

When the stabilizing cylinder, located on one side of the support comes to rest on the ground, it is created in its hydraulic supply circuit 101 an overpressure which is detected by one of the pressure detecting means 102.

Furthermore, there are provided position detector means 103 arranged to detect the position of the arm, in a horizontal plane, with respect to the axis of symmetry on either side of which the supports on the ground are situated.

The signals emitted by the pressure detector means 102 and the position detector means 103 are compared in comparator means 104. These comparator means generate an output signal when the two stabilizing jacks are not in contact with the ground or, if a only cylinder is in support, when the arm leaves the angular sector associated with this cylinder, for example when the arm leaves the right or left scanning semicircle (considered with respect to the axis of symmetry on either side of which are located the jacks), when only the right jack or the left jack are supported respectively.

The output signal from the comparator means 104 causes the closure member 3 to control the flow of the hydraulic fluid supplying the actuating cylinder of the arm in a vertical plane and / or supplying the rotation control cylinder of the arm in a horizontal plane (not shown in FIG. 6), in the same way as the pressure sensing means 2 act in the event of the arm being overloaded (as described above with reference to FIG. 1).

The output signal of the comparator means 104 also causes the detection means 5 of the angular position of the arm to be put into operation or to be switched on so that they select the or a movement sequence 6 that it is possible to do follow the arm to cause only a decrease in the moment of the load, with opening of the control member 4 obtained in 7, with priority over the closure ordered in 3, to authorize the movement of the arm according to the required sequence.

Ultimately, the comparator means 104 act so as to block the operation of the arm of the lifting device, thus avoiding any risk of overturning the assembly.

The user can then continue with the desired maneuvers only when at least one jack has been brought to bear on the ground or else can only pivot the arm horizontally to bring it back into the appropriate angular sector.

However, the obligation, in this case, to maneuver the arm, once the safety system has been activated, to cause a reduction in the moment of the load may be too restrictive for the user and, in most cases, it is possible to arrange the assembly in such a way that this maneuver is not made compulsory, without, however, safety being affected, as will be explained with reference to FIG. 8.

Furthermore, it is generally recommended that the lifting device is in a predetermined position relative to a horizontal plane. In particular, when the lifting device is mounted on the platform of a truck, this platform must be in a roughly horizontal plane so as to avoid overturning of the assembly due to a slope.

To this end, provision is made for attitude detector means 105 capable of generating, when the lifting device is not in the required position relative to the horizontal plane, a signal causing at 3 the closure of the member 4 of control of the movement of the arm in a vertical plane and the triggering of the security system 5, 6, 7 to authorize only the nano-operations of the arm according to a sequence reducing the moment of the charge.

In addition to the arrangements which have just been described and which are intended to ensure safety during operation of the lifting device, in particular by prohibiting movement of the arm other than in a sequence, only allow a reduction in the moment of the invention also provides for very provisions which aim to authorize, in a certain number of pre-established circumstances, maneuvers of the arm despite the activation of the general security system.

When the arm is raised to the maximum and it reaches the stop in its maximum high position, it appears in the hydraulic circuit supplying the control cylinder an overpressure of sufficiently large value to cause the triggering of the pressure detector means 2 and therefore the activation of the security system 5, G, 7. The arm is then blocked.

It should be noted that this overpressure is only due to the overpressure which is independent of the load state of the arm and which therefore appears even when the load is low or zero. The security system then prohibits the lowering of the arm because such a movement would correspond to an increase in range of the arm, therefore an increase in the moment.

To overcome this drawback, position detector means 106 are implemented which detect the abutment of the arm in its maximum high position. When the arm reaches said position, the detector means 105 generate a signal causing at 7 the opening of the control member 4 authorizing the lowering of the arm.

This lowering is carried out over a very short distance and is sufficient to bring the pressure in the hydraulic supply circuit of the jack to a normal value and, at this moment, the arm is out of the zone of action of the detector means 108 .

Under these conditions, if the arm is not in an overload state, the normal value of the pressure of the hydraulic circuit does not influence the pressure sensor; the safety system is therefore no longer in operation and the lowering of the arm can be continued.

On the other hand, if the arm is in an overload state, the momentary overpressure disappears, but the pressure remains sufficient to trigger the pressure sensor the safety system remains on, preventing further lowering of the arm. The rest of the operations must then take place in the manner described above from Tanière to reduce the moment of charging,

In addition, the manufacturing standards and specifications relating to lifting devices stipulate that these lifting devices must, as a safety measure, be able to withstand overloads in relation to the maximum loads normally provided for.

Therefore, it is necessary to be able to temporarily subject, during tests, the lifting devices to determined overloads.

In addition, during use, it may be necessary to operate the lifting devices outside these normally provided limits, due to exceptional circumstances, for example following an accident, under the control of a person. authorized.

However, the implementation of the safety provisions set for normal conditions of use prevents the limits initially set being exceeded.

To occasionally allow the lifting device to operate under conditions that would normally cause the safety system to be put into service, provision is made to equip the lifting device with a shunt device 107, which can be operated manually as symbolized by the arrow 108 by an authorized person. The actuation of the shunt device 107, on the one hand, causes the physical destruction of a member 109 of the lifting machine and, on the other hand, causes the opening 4 of the control member 4 of the arm , thus authorizing any movement of the arm.

The member 109 is not directly accessible (it is for example placed in a sealed enclosure) and can therefore only be replaced by an authorized person: thanks to this arrangement there remains physical evidence of the actuation of the shunt device 107 .

Referring to Figures 7 and 8, we will now describe an embodiment of the complementary arrangements. which have just been presented with reference to FIG. 6.

For greater clarity, the security system of the invention is shown in two parts corresponding respectively to FIGS. 7 and 8, these two parts being interconnected at points a and d.

FIG. 7 represents the security system of FIG. 5 to which the shunt device and the detector means have been added, detecting the coming of the arm in abutment in its maximum high position which have been described above in general.

In FIG. 7, the elements identical to those of FIG. 5 are designated by the same reference numbers.

The shunt device includes a switch 112 with double contact.

For the first contact 112a, one of the terminals is connected to ground while the other terminal is connected to the terminal brought to the positive potential of contact 72a of relay 72.

For the second contact 112b, one of its terminals is brought to positive potential while its other terminal is connected, via a signaling lamp 113, to the cathode of diode 74. An isolation diode additional 114 is inserted between the diode 74 and the solenoid valve 54.

Furthermore, to the cathode of diode 74 is connected the anode of an isolation diode 115, the cathode of which is joined to that of diode 75, which is itself connected to the anode of another diode. isolation 116 whose cathode is connected to that of diode 76.

In addition, an isolation diode 117 is inserted between the cathode of the diode 75 and the solenoid valve 55.

Furthermore, a fuse 118 is inserted between the positive pole of electrical supply and the terminal joined to this pole of contact 72a of relay 72.

The functioning of the shunt device is the following boast.

The switch 112 normally being in opening, as shown in FIG. 7, one acts manually on it as symbolized by the arrow 119 to close it.

When contact 112a is closed, the positive pole of electrical supply is connected to ground via fuse 118, which is destroyed. As a result, the positive polarity is no longer transmitted to the contacts of the relay 67, the coil of the relay 72 is no longer energized, causing the opening of the contact 72a and the closing of the contact 72b: the safety system is thus activated. function, normally only allowing movements of the arm likely to reduce the load moment.

However, at the same time as the contact 112at the contact 112b is closed, thus bringing the + polarity in the lamp 113 (which lights up to signal the commissioning of the shunt device) and in the line connecting the cathodes of the diodes 74, 75 and 76. As a result, the control coils of the solenoid valves 54, 55 and 56 are exited and the corresponding solenoid valves are open, authorizing all the controls of the jacks which they supply, despite the activation of the safety system .

As regards now the means for detecting the coming of the arm into abutment in its maximum high position, a position detector 120 is provided, for example having a movable finger 121 able to cooperate with the arm when the latter reaches the aforementioned maximum high position and to be pushed back by it to close an electrical contact.

The detector 120 has a terminal connected to the + pole while its other terminal is connected to the terminal of the coil of the relay 72 which is not grounded.

When the arm comes to a stop in its maximum high position, it was indicated previously that this resulted in an overpressure in its hydraulic circuit control, overpressure which is detected by the corresponding pressure sensor (the sensor 63 in the case shown in Figure 7), causing the opening of the contact 68 and the de-energization of the coil of the relay 72 .: the system of security should normally be activated.

However, when reaching the maximum high position, the arm pushes the movable finger 121 of the detector 120 and causes the appearance of positive polarity on the output line of the detector: under these conditions, the coil of the relay 72 is kept energized, and the security system does not operate.

Therefore the arm can be lowered, but only over a very short distance corresponding to the stroke of the movable finger 121. Then, as soon as the internal electrical contact of the detector 120 is open, or the lowering of the arm can be continued s 'it is not overloaded, or else, the arm being overloaded, the line of relay 72 is no longer energized and. the safety system activated requires following the sequence aimed at reducing the moment of charging.

Referring to FIG. 8, we will now describe the other additional arrangements intended to be associated with the security system of FIG. 7.

In this figure, it has been assumed that the lifting device is fixed to the chassis 122 of a truck (partially shown with its rear axle 123), just behind the driver's cab (not shown), the space available behind of the lifting device which can for example be occupied by a platform or a bucket (not shown), intended to receive a load.

In addition, for clarity, only the lower support 124 of the lifting device has been shown. This support 124 comprises, on the one hand, a barrel 125, extending substantially vertically and at the free upper end of which is articulated the arm or the first movable arm (not shown), and, on the other hand, a plate 126 supporting the barrel 125 and movable in rotation, relative to the chassis 122, the plate 126 and the barrel 125 being integral with one another.

Substantially to the right of the platform 126, the frame. 122 also supports a hollow cross member 127 extending over the entire width of the chassis approximately perpendicular to the longitudinal axis of the truck. This cross member 127 serves as a housing for two beams 128a and 128b which can be moved inside the cross member so as to be able to occupy either a first position in which they have returned inside the cross member, or a second position in which they are crossbar exits and project laterally.

At their free ends, the beams 128a and 128b respectively carry double-acting cylinders 129a and 129b, arranged substantially vertically, the pistons of which are terminated by a foot 130a and 130b, respectively, intended to come to bear on the ground.

The exit or re-entry control of the beams 128a, 128b can be of any suitable type, for example being a hydraulic control. However, this command not intervening in the understanding of the invention, it has not been shown to simplify the drawing.

The cylinders 129a, 129b are controlled hydraulically by means of a three-position distributor 131, connected to the two chambers of the cylinders 129a, 129b.

The rotation control of the plate 126 can be carried out, in a conventional manner, by means of a rack 132 actuated by a double-acting hydraulic cylinder 133, which is supplied by means of a distributor 134,

In the supply circuit of one of the chambers of the jack 133 (for example that of the left chamber in FIG. 8), there is inserted a solenoid valve 135 whose role will be explained later.

To the hydraulic supply circuits of the cham upper legs of the jacks 129a, 129b are respectively connected to the pressure sensors 136a, 136b which control electrical switches inserted in electrical circuits connected between the polarity + and the ground by means of the relay coils with a single contact 137 and 138 , respectively.

Furthermore, two position detectors 139 and 140 are provided, situated respectively to the left and to the right with respect to the longitudinal axis of the truck, for detecting the position of the arm of the lifting device with respect to this axis, c ' that is to say to detect whether the arm is turned towards the left side (semicircle 141 of scanning left) or towards the right side (semicircle 142 of scanning right). The position detectors are respectively inserted into electrical circuits connected to ground via the single-contact relay coils 143 and 144, respectively.

In addition, two position detectors 145 and 146 are provided, associated respectively with beams 128a and 128b, for detecting the extended or retracted position of the latter.

The position detectors 145 and 146 are inserted in respective electrical circuits connected to ground via the relay coils 147 and 148, respectively.

As shown in FIG. 8, all the contacts of all the relays 148, 138, 144, 137, 143 and 147 are connected in series, the free contact of the relay 148. and that of the relay 147 being connected to the + pole.

In addition, signal lamps 1.49 and 150 are connected, between the + pole and the points common to the contacts of relays 144 and 137, in parallel respectively with relays 148, 138, 144 and with relays 137, 143, 147. isolation diodes 151 and 152 are connected in series respectively with lamps 149 and 150.

The common point for the contacts of relays 137 and 144 is connected to ground via the coil of a relay 153, one of the terminals of the contact of which is connected to the + pole.

The assembly which has just been described constitutes a detector assembly of the support on the ground of the stabilizing jacks 129a and 129b which is connected to the security system of FIG. 7 in the manner which will be indicated a little further on, and whose operation will be explained later.

In addition to this assembly, attitude detection means are provided comprising a device 154 detecting the horizontality of the chassis 122 of the vehicle, both in the transverse direction and in the longitudinal direction.

The device 154 may for example be constituted by an electrically conductive rod 155 secured to the frame so as to hang freely in the manner of a pendulum. This rod is at ground potential.

Around the free end of the rod 155 is arranged a ring 156, also electrically conductive, and brought to the positive potential, the rod passing substantially in the center of the ring when the chassis is horizontal. The ring 156 is connected to one terminal of the coil (the other terminal of which is connected to ground) of a relay 157.

A terminal of the contact of relay 157 is connected to the free terminal of the contact of relay 153 while its other terminal is connected to point a which, in FIG. 7, constitutes a terminal of the coil (the other terminal of which is at the ground) of a relay 158. The contact of relay 158 is connected, on the one hand, to the non-grounded terminal of the coil of relay 72 and, on the other hand, to the common point at contact 70a of the relay 70 and of the switch 6B actuable by the pressure sensor 63.

According to the arrangement which has just been described, the contacts of the relays 153 and 157 and the coil of the relay 158 are connected in series. In this way, the attitude detecting means and the support detecting means stabilizing jacks on the ground shown in Figure 8, and the overload detector means shown in Figure 7 are connected in series and act in series to energize the relay coil. 72, that is to say that, in the case where one of these means no longer satisfies pre-established conditions, the coil of the relay 72 is no longer energized, as will be explained in more detail later when will be indicated the operation of the assembly.

In addition to the above arrangements, provision is also made to equip the lifting device with means intended to limit its rotation, in a horizontal plane, to a determined angular sector, in order to prevent p ₃ r example that the arm and / or the load does not strike an obstacle. This is particularly the case when the lifting device is mounted on a truck platform, just behind the driver's cab; the arm should be allowed to rotate above the platform to allow loading or unloading, but should be prevented from rotating on the side of the driver's cab to avoid damage to the driver's cab.

The angular sector which the lifting device is authorized to sweep is shown at 159, with shading, in Figure 8.

For this purpose are arranged on either side of the chassis and transversely to the vehicle axis, two proximity detectors 160 and 161. Preferably these detectors are located in different horizontal planes so that the control means , linked in rotation to the plate 126, of one of the detectors cannot act on the other detector when the arm has rotated 180 °.

The detector 130b covers the sector between 0 and 90 ° and the detector 130a covers the sector between 90 ° and 180 °, the two detectors being arranged so that their respective areas of action overlap at point 90 °.

The detectors 160 and 161 are inserted into respective electrical circuits connected to ground via the relay coils 162 and 163, respectively.

The relay contact terminals are respectively connected together in pairs so that the contacts are connected in parallel. One of the common points is joined to point a, while the other common point is joined to respective first terminals of two switches 164 and 165. The second terminals of these switches are connected together and connected to a terminal of the coil (whose other terminal is grounded) of a relay 166.

The switches 164 and 165 are mechanically linked to the hydraulic distributor 134 controlling the rotation of the plate and the barrel of the lifting device, so that one or the other of these switches is closed, depending on whether the distributor is actuated in one way or the other.

One terminal of the contact of relay 166 is connected to the cathode of an isolation diode 167, the anode of which is connected to point a, while its other terminal is connected to point d (which, in FIG. 7, is located between the switch 112 and the signaling lamp 113 of the shunt device described above) and to one terminal of the coil (the other terminal of which is grounded) for controlling the solenoid valve 135.

We will now indicate the operation of the devices shown in Figure 8 and which have just been described.

When the chassis of the vehicle is horizontal, the rod 155, passing through the center of the ring 156, is not in contact with the latter. The ₊ polarity, to which the ring 156 is worn, is thus transmitted to the coil of relay 157, which excited, keeps the contact of said relay closed.

When the beams 128a and 128b are in the extended position and the stabilizing jacks 129a and 129b are resting on the ground, the stability of the assembly is ensured and the barrel 125 can rotate and the arm can be brought in, without danger of either side of the vehicle. Under these conditions, the relays 148, 138, 144, 137, 143 and 147 (whose coils are excited) on their respective closed contacts and the ₊ polarity is brought to the coil of the relay 153 which, excited, keeps the contact of said closed relay (detailed operation will be given later).

In this way the polarity + is transmitted, by the closed contacts of relays 153 and 157, to the coil of: relay 158, the contact of which is also closed.

Under these conditions, the signal emitted by the overload detection device is transmitted, via the closed contact of the relay 158, to the relay coil 72.

The operation of the security system is then identical to that indicated _for Figure 5.

Furthermore, when the arm is in the authorized sector 159, the rotation limiting means (the operation of which will be explained later) provide the coil of the relay 166 with + polarity and the contact of this relay is closed: + polarity , transmitted to point a by the contacts of relays 153 and 157, is also transmitted, via the contact of relay 166, to the control coil of the solenoid valve 135 which is then in the on position. As a result, the hydraulic fluid can circulate in the corresponding hydraulic circuit and the rotation of the lifting device can be controlled using the hydraulic distributor 134.

In the case where, on the other hand, the chassis of the vehicle is not horizontal, the rod 155 comes into contact with the ring 156 and, the rod being connected to earth, the bo bine of relay 157 is no longer energized: the contact of this relay opens. The ₊ polarity is no longer transmitted to the coil of relay 158, it is no longer energized and the contact will correspond: opens, removing the excitation of the coil of relay 72. Under these conditions, contact 72a opens tightly as contact 72b closes by activating the security system.

In addition, the control coil of the solenoid valve 135 no longer being energized, the hydraulic circuit for controlling the barrel rotation is locked and the rotation can no longer be carried out.

The lack of horizontality of the chassis therefore has the same consequences as an overload of the arm. and, thanks to the activation of the security system, leads the user to be able to maneuver the arm only in a sequence reducing the moment of charging.

Security against any overturning of the assembly is therefore ensured.

We will now indicate the detailed operation of the means for detecting the ground support of the stabilizing jacks.

When the stabilizing cylinders 129a and 129b. are controlled so that the feet 130a and 130b are in contact with the ground, the coming into support of the feet generates, in the hydraulic control circuit, an overpressure which is detected by the pressure sensors 136a and 136b, which cause the supply of the coils of relays 137 and 138 and the closing of the corresponding contacts.

The descent of the legs 130a and 130b could be controlled without the carrying beams 128a and 128b having come out: in this case, however, the width of the support on the ground would be less and the risk of overturning the assembly would not be dismissed.

To eliminate this possibility and be assured of a maximum width of support on the ground, the position detectors 145 and 146 are arranged to detect the extended position of the beams 128a and 128b and, only in in this case, supply + polarity to the coils of relays 147 and 148 which, excited, cause the corresponding contacts to close.

Under these conditions, one or the other of the position sensors 139 or 140 is in operation depending on whether the arm scans the left sector 141 or the right sector 142, respectively, and causes the contact closure of the corresponding relay 143 or 144, respectively.

The ₊ polarity is then supplied to the coil of the relay 153 either by the circuit of the contacts of the relays 148, 138 and 144, or by the circuit of the contacts of the relays 147, 143 and 137.

With the contact of relay 157 closed, the + polarity is then brought to point a and, as in the circumstances indicated above, the coil of relay 72 is energized. The arm can then be maneuvered normally.

On the other hand, if the beams 128a and 128b are not extended and / or if the jacks 129a and 129b are not in contact with the ground, the contacts of the relays 147 and 148 and / or of the relays 137 and 138 are open. The coil of relay 153 is no longer energized and, the contact of this relay being open, the absence of excitation of the coil of relay 158 causes the coil of relay 72 to de-energize: the arm is then locked in position and the security system is activated. Simultaneously the lamps 149 and 150 light up to signal the anomaly.

In order for the arm operations to be carried out, the user must control the exit of the beams and the support of the cylinders.

It is now assumed that one of the jacks, for example the jack 129a, is properly supported on the ground, but that the other jack 129b has not come out, for example due to the lack of space available on the side of the vehicle to take out the beam 128b.

The contacts of relays 137 and 147 are then closed, but on the other hand the contacts of relays 138 and 148 remain open, since the corresponding coils do not are not energized, The lamp 151 is then lit.

Under these conditions, the arm can traverse the angular sector 141 situated on the left, without the stability being affected, but on the other hand it must not traverse the angular sector 142 situated on the right because, the chassis not being supported on this side , the whole unit could tip over.

As long as the arm scans the angular sector 141. the position detector 139 is in operation and excites the coil of the relay 143. Therefore the + polarity is applied to the coil of the relay 153 by means of the contacts of the relays 147 , 143 and 137.

On the other hand, as soon as the arm reaches the axis of the vehicle, the position detector 139 is no longer in operation and, the coil of the relay 143 being no longer energized, the corresponding contact opens, causing, on the one hand, the de-excitation of the coil of the relay 72 and the commissioning of the security system and, on the other hand, the de-excitation of the coil of the relay 135 and the blocking of the arm in rotation.

In addition, simultaneously the coil of the solenoid valve 135 is no longer energized and the solenoid valve closes the hydraulic circuit for controlling the rotation of the arm.

One finds oneself placed in substantially the same case as that which has just been described (only one support on the ground) when the two stabilizing jacks are in support on the ground and that the arm is in operation while being strongly separated from the longitudinal axis. of the vehicle, for example directed perpendicular to this axis.

The assembly is not sufficiently stable, in particular when the arm is loaded, so that the two feet 130a and 130b remain simultaneously supported on the ground: if the arm is for example directed to the left (scanning of the angular sector 141), the cylinder 130a will be overloaded while the cylinder 130b, on the contrary unloaded, will no longer be supported on the ground: the overpressure which existed in its hydraulic control circuit disappears, which causes, via the pressure sensor 136b, the opening of the contact of relay 138.

However, as in the previous case where a single jack was extended and in support, the relay 153 is energized by means of the contacts of the relays 147, 143 and 137, and the operations of the arm can be carried out normally.

If one wishes to rotate the arm to work in the angular sector 142, at the moment when the arm passes approximately in the longitudinal axis of the vehicle, the loads are approximately equally distributed between the two lateral supports and the foot 130b returns to contact with the ground, thereby closing the contact of relay 138.

Then when the arm is in the angular sector 142, it is on the contrary the foot 130a which leaves the ground, causing the opening of the contact of the relay 137. The maneuvering of the arm remains however always possible since the relay 153 is now energized via the contacts of relays 148, 138 and 144.

We will now describe the operation of the rotation limiting means.

It is first assumed that the arm is in the 90 ° position, that is to say in the axis of the vehicle. As the angular sectors controlled by the proximity detectors 160 and 161 overlap slightly, for the 90 ° position, the + polarity is transmitted respectively to the coils of the relays 162 and 163, the contacts of which are kept closed.

However, the hydraulic distributor 134 controlling the rotation is then in the neutral position and, therefore, operates neither the switch 164 nor the switch 165 which are open.

Consequently, the coil of relay 166 is not supplied and the contact of said relay is open: the coil of solenoid valve 165 is not energized, the elec valve cuts the hydraulic circuit supplying the rotation control cylinder 133. Under these conditions, the lifting device is hydraulically locked in the 90 ° position, which can be of great interest to prevent the arm from turning by itself, for example in the presence of a cant of the chassis which supports it. .

If it is desired to pivot the lifting device, from the 90 ° position which has just been envisaged, to bring it to the right (towards the 0 ° point), the hydraulic distributor 135 is actuated, this which, due to the mechanical connection which binds them, causes the closing of the switch 165.

The + polarity is therefore brought, through the relays 153, 157 and 163 and the switch 165, to the coil of the relay 166, the contact of which is closed. The + polarity thus feeds, through the diode 167 which is then on, the control coil of the solenoid valve 135; the solenoid valve closes the hydraulic circuit supplying the jack 133 to allow the rotation of the device.

When the hoist reaches the. position 0 °, the proximity detector 161 interrupts the positive supply of the coil of the relay 163, which has the effect of interrupting the electrical circuit connecting the coil of the relay 166 to the + pole.

As, moreover, when the lifting device traverses the sector 0 ° -90 °, the switch 164 is not actuated by the hydraulic distributor 134 and remains open, it follows that the coil of the relay 166 is no longer energized, which causes the contact of the relay 166 to open and the solenoid coil 135 to de-energize. The actuator supply circuit 133 is interrupted and the lifting device is hydraulically locked in this position, even if the hydraulic distributor 134 is held in the position it occupies.

On the other hand, the distributor 134 can at this stage be operated in opposite directions, which has the effect of closing the switch 164. As the detector 160 remains in function when the lifting device is in the angular sector 0 ° -90 °, the polarity + reaches the coil of relay 166 via relays 153, 157 and 162 and of switch 164. As a result, the solenoid valve 135 restores the continuity of the hydraulic circuit controlling the jack 133 and the lifting device rotates in direction 0 ° → 90 °.

Furthermore, if the security system has been activated following the opening of the contact of relay 153 and / or of relay 157, actuation of the shunt device described above brings point d to the + polarity, and the solenoid valve coil is energized, allowing the lifting device to rotate.

As it goes without saying, and as it already follows from the foregoing, the invention in no way limits to those of its modes of application and embodiments which have been more especially envisaged; on the contrary, it embraces all its variants.

Claims (16)

1. Hydraulic lifting device comprising two arms hinged to one another and actuated by respective hydraulic jacks, each arm being able to be raised beyond the extension of the arm which precedes it, said lifting device comprising, on the one hand, pressure detector means for detecting the pressure of the supply circuit of the aforesaid hydraulic cylinders, these pressure detector means being arranged to block the arms as soon as the moment of the load generates a pressure greater than a predetermined value , on the other hand, means of security control of the movement of the arms which are arranged to, first of all, be put into operational position by said pressure detector means and to, then, authorize the control of the arms only according to a sequence which reduces the moment of the load and, secondly finally, angular position detecting means associated with each arm and each arranged to deliver two representative signals s of the position of the arm in question situated respectively above and below the horizontal passing through the articulation of said arm, characterized in that: - when the two arms respectively occupy positions located above a first and a second horizontal passing respectively through their articulations, the safety control means are controlled by the position detector means in such a way that they allow raising the first and / or second arms, but prohibiting their lowering, - When the first arm occupies a position above the first horizontal and the second arm occupies a position below the second horizontal, the safety control means are controlled by the position detecting means in such a way that '' they prohibit any movement (raising or lowering) of the first arm, but allow lowering of the second arm by prohibiting its raising, - And, when the first arm occupies a position located below the first horizontal, the safety control means are controlled by the position detector means _in such a way that they allow the lowering of the first and / or of the second arm, but prohibit their raising. ₂ . Hydraulic lifting device according to claim 1, characterized in that the angular position detecting means associated respectively with the first and second arms are arranged to have the horizontal and the vertical respectively for reference. 3. Hydraulic lifting device according to claim 2, characterized in that the detector means associated with the second arm are pivotally fixed to said arm. ₄ . Hydraulic lifting device according to any one of claims 1 to 3, characterized in that, the second arm being provided with at least one hydraulic extension, the safety control means are arranged to not allow the movement of the 'extension only in the direction of its retraction and prohibit its movement in the direction of its exit. 5. Hydraulic lifting device according to any one of claims 1 to 4, equipped with a load lifting winch, characterized in that the pressure detecting means control the control of the winch so that, when said means detect a pressure higher than a determined pressure, they prevent the lifting of a load from its plane of rest. 6. Hydraulic lifting device according to any one of claims 1 to 5, characterized in that, the last arm or the last hydraulic extension which can be extended by means of at least one mechanical extension, the detector means of pressure include at least two pressure sensors each of which is calibrated for a predetermined number of extensions (counted from 0 when no extension is used), first selection means being provided to automatically select the appropriate pressure sensor according to the number of mechanical extensions extended. 7. Hydraulic lifting device according to any one of claims 1 to 6, characterized in that the safety control means comprise limit switches associated with the control valves for actuating cylinders of the arm or arms and / or hydraulic and / or winch extensions and in that said switches are inserted into electrical supply circuits for solenoid valves for controlling said jacks, second selection means, controlled by the angular position detector means, selecting the switches suitable for allowing only the movement of the arm (s) reducing the moment of the load. 8. Hydraulic lifting device according to claims 6 and 7, characterized in that the first and second selection means each comprise a relay with two stable states. 9. Hydraulic lifting device according to any one of the preceding claims, characterized in that detection means are provided for detecting the abutment of the arm or of the assembly of arms in the maximum high position - coming into abutment causing an overpressure in the supply circuit of at least one hydraulic cylinder, which leads, by means of pressure detecting means, to bringing the safety means into operational position and therefore blocking the arm or all of the arms and the impossibility of lowering it or these - and to authorize, from said maximum high position and despite the operational position of the safety means, lowering, over a very short distance , arm or arms. 10. Hydraulic lifting device according to any one of the preceding claims, equipped with at least two lateral stabilizing jacks for supporting the ground, characterized in that it comprises means for detecting the support on the ground of the stabilizing jacks functionally associated with the safety control means to block the arm (s) when at least one jack is not in contact with the ground or else, in the case where only one stabilizing jack is in support on the ground and where the arm or arms are moved in horizontal rotation, when the center of gravity of the assembly reaches a limit of the support polygon. 11. Hydraulic lifting device according to claim 10, characterized in that the means for detecting the support on the ground of the stabilizing jacks comprise position detectors capable of detecting the lateral exit of beams carrying the above said stabilizing jacks, pressure sensors capable of detecting the overpressure prevailing in the hydraulic circuits of the said stabilizing cylinders when these are in contact with the ground, position detectors capable of detecting the angular orientation of the lifting device, and comparator means capable of delivering a signal authorizing the operations of the lifting device only if the position detectors and the pressure sensors detect predetermined conditions. 12. Hydraulic lifting device according to any one of the preceding claims, characterized in that it includes attitude detector means functionally associated with the safety control means for blocking the arm (s) so as not to allow movement of the or arms only if the lifting device is in a predetermined suitable position. 13. Hydraulic lifting device according to claim 10 or 11 and claim 12, characterized in that the means for detecting the support on the ground of the stabilizing jacks, the means for detecting attitude and the means for detecting the pressure of the hydraulic circuit of the control of the arms are connected in series so that the security control means are put into the operational position by one of the above means. 14. Hydraulic lifting device according to any one of the preceding claims, characterized in that it comprises rotation limiting means for limiting the horizontal rotation of the arm (s) in a predetermined angular sector. 15. Hydraulic lifting device according to any one of claims 10 to 14, characterized in that there are provided means for hydraulic locking of the rotation of the lifting device controlled by the means for detecting the support on the ground of the jacks. stabilizers, by the attitude detecting means or by the rotation limitation means when these detect an abnormal condition. 16. Hydraulic lifting device according to any one of the preceding claims, characterized in that it comprises a shunt device arranged to, when actuated, bypass the safety system and allow the operation of the machine. lifting under conditions normally causing said safety system to be brought into operational position, the shunt device being further arranged so that its actuation causes permanent destruction of an element of the lifting device, said element not being accessible to an unauthorized person.

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