FR2483903A1 - Safety system for hydraulic lifting appts. - uses dual-threshold hydraulic pressure detection systems controlling movements of lifting arms - Google Patents

Abstract

The appts. may be used on a vehicle-mounted crane with a base column jointed to two arms with operating rams. When the lower pressure threshold is attained due to increase of the angle between the arms, further movement and extension of the telescopic arm are prevented. When the lower threshold is attained by extension of the telescopic arm without modification of the angle, further extension of the arm and retraction of the ram rods are prevented. When the upper threshold (corresp. to the max. allowable pressure) is attained, telescopic extension remains impossible and extension of the ram rods is inhibited whilst their retraction is permitted. Total safety is ensured by the impossibility of any movement of the hydraulic control, including rotation of the base and movement of the stabilising props. Telescopic extension locking jacks, their supply valves and hydraulic or electrical accessories are eliminated. An electric circuit feeds a solenoid valve and a dual threshold pressure controller.

Description

 The present invention relates to a safety system for a hydraulically controlled lifting device.

This system can be applied in particular to a hydraulic crane, shown in Figure 1 of the accompanying schematic drawing, and comprising a base column 2 on which is articulated a first arm 3 at the other end of which is articulated a telescopic arm 4, it it is important to have permanent information on the position of the point of application of the load P at the end of the arm te 'copicates them 4 relatively to two horizontal planes H1 and H2 containing, respectively, the axis of articulation 01 of the arm 3 on the base column 2 and the articulation axis O2 of the telescopic arm 4 on the arm 3.

 If it is necessary to know the direction of movement of the cylinder rods V1 and V2 making it possible to vary respectively the angle a formed by the column 2 and the arm 3 and the angle ss formed by the arm 3 and the arm 4, it is also important to know the effects of these movements.

 In fact, if the point of application of the load is located above the two planes H1 and H2 and the maximum tolerated effort is reached by leaving the telescope 4, the retraction e of the rods of the cylinders V1 and V2 allowing a lowering the load will correspond to an increase in effort, generating unacceptable pressures in these cylinders. It is therefore advisable to prohibit these re-entry movements of the rods. On the contrary, if the rods of the cylinders V1 and V2 are brought out from this position, there is a reduction in the pressure. It is therefore desirable that this movement is possible because it has no dangerous implications.

 If the point of application of the load P at the end of the telescope 4 is located below the two planes H1 and H2, and a limit value is reached by output from the telescope 4, the output of the rods V1 and V2 will correspond an increase in the pressure in the cylinders which, if it reaches a tolerable limit value, must be prohibited.

Insofar as the point of application of the load is situated between the planes Hl and H2, as in the example represented in FIG. 1 of the attached schematic drawing, the output of the rod of the jack V1 must be possible because it corresponds to a reduction in the force, but the output of the rod of the cylinder V2 corresponding to an increase in the torque, should only be possible if the pressure in the cylinders V1 and V2 does not exceed the permitted value.

To this end, in the device equipping this crane, each jack allowing the angular variation of two arms is equipped with a pressure detection device comprising two thresholds, the one detecting the highest pressure corresponding to the allowed limit pressure, the means actuators being such that
- when a pressure corresponding to the lower threshold is reached by increasing the angle formed by two arms of the apparatus, the continuation of the movement is prohibited, as is the exit from the telescope 4 and that,
- when a pressure corresponding to the lower threshold is reached without modifying the angles formed by the different arms but by lengthening a telescopic part that includes one of them, the exit from the telescope is made impossible, as are the re-entries of rods of the jacks, corresponding to a reduction in the respective angles which the different arms form, the exit of the rods from these jacks being possible and the increase in the angles which the different arms form being carried out insofar as the second threshold n is not reached, while if this second threshold is reached, the exit from the telescope remains impossible and the exit of the rods of the articulation cylinders of the arms is made impossible, while their return is authorized
This arrangement makes it possible, thanks to the second pressure threshold detected, to assess the position of the point of application of the load by interpreting the effects consecutive to the variation of position of this point of application of the load relative to the two planes. H1 and II2 whose H1 is fixed and whose H2 is variable in height.

 However, the means used to block the movement if necessary, as described in the previous device, are relatively complex since they act mechanically on the dispenser itself, from a hydraulic or electric control.

 This solution has the disadvantage of a high price and of not allowing adaptation on any type of matriez.

It should be noted that the known devices require, in addition, the use of electric current as well as a system placed on the supply of hydraulic fluid to the cour distributor Distributing the hydraulic flow to the tank in the event of a lack of current on the information system.

 This short-circuit system notably includes a solenoid valve which allows the hydraulic fluid to supply the distributor. If the electric current is established on the entire safety system. This continuous verification can be carried out using a low current, which detects any anomaly, called "monitoring current".

 The present invention aims to provide a security system in which the active monitoring circuit is integrated as an active element.

To this end, in the system which it concerns, of the type comprising, associated with each jack allowing the angular variation of two arms, a pressure detection device comprising two thresholds, the one of which detecting the highest pressure corresponds to the allowed limit pressure, as well as devices for detecting the direction of actuation of each control of the distributor, characterized in that the information provided by the pressure detection devices controls an EVS solenoid valve mounted on the safety circuit of the hydraulic system.

 Therefore, when a dangerous pressure is reached, there is an interruption in the current supply to the solenoid valve, which has the effect of interrupting the supply of the device with hydraulic fluid.

 it follows an impossibility for the operator to carry out or to continue a dangerous operation, the hydraulic device keeping the device in state as a result of the presence of non-return valves hydraulically controlled.

This security system has many advantages, the main ones being as follows
- Be sure that the security system is in working order.

- Ensure total safety due to the impossibility of any hydraulic control movement, including the rotation of the base and the movement of the stabilizing legs in the case of a crane mounted on a vehicle.

 - Use a solenoid valve both for the circuit monitoring system and as a device for securing the device.

 - Allow the installation of such a system on many types of devices without modification or addition to the basic construction elements.

 - Allow the overpressure of the locking cylinders of the drawer, as well as the solenoid valve supplying them and the various hydraulic or electrical accessories.

 - Allow the solenoid valve to be mounted at any point on the distributor's supply line, which allows adaptation to any type of device.

- Limit system maintenance since a solenoid valve is a very wide accessory.

Advantageously, the circuit. The electrical system with which the security system is fitted comprises a first electrical supply line A1 which, under normal operating conditions, supplies the detection device for the first threshold and the second pressure threshold, and a second supply line electric ensuring, after reaching the first threshold, the supply of a block which detects the movements carried out, which gives the orders to prohibit the continuation of the aggravating movements1 which stores in memory the movement which created the fault and which reautorises the initiation of the hydraulic system when the movements carried out are aggravating.

 According to another characteristic of the invention, the safety block is arranged in such a way that, insofar as a worsening movement is exerted temporarily, it keeps in memory the movement having created the defect and that, insofar as the dagging movement is exerted long enough to bring the pressure below the first threshold, it erases the memories, cuts the power supply by the second line, and resumes the power supply to the electro - valve by the first line.

 In addition, upon reaching the second threshold, an inversion of the memories occurs, by erasing the information corresponding to the movement having caused the first threshold to be reached and simultaneously memorizing the fault which has caused the second threshold, thus re-authorizing reverse movements to those which made it possible to reach the second threshold.

 On the electrical supply line of the safety solenoid valve, is mounted a relay supplied according to the removal of the system either by the first line or by the second line, and comprising a contact associated with each control of the distributor corresponding to the jacks articulation, the contacts corresponding to crossed movements of two cylinders being mounted in parallel.

When the dispenser is actuated, a contact opens in accordance with the movement made.

If there is no cross movement due to the parallel mounting, the solenoid valve will be supplied by at least one relay conductor. If, on the contrary, the operator crosses the movements of two cylinders, the relay will no longer supply the solenoid valve and will put the system in safety.

In any case, the invention will be clearly understood with the aid of the description which follows with reference to the appended schematic drawing representing, by way of nonlimiting example, an embodiment of the electrical circuit which this security system comprises. , which is shown in Figure 2
Figure 3 of this drawing shows the different actuation possibilities of a distributor associated with a crane according to Figure 1 and having two arms 2 and 3 hinged one on the other and a telescopic arm.

The electrical diagram shown in the drawing includes two supply lines, respectively AI, A2 and a return line A3. This electrical circuit supplies in particular an EVS solenoid valve, as well as a pressure detector with two thresholds bearing the respective references 51 and 52.

The various movements of the distributor shown diagrammatically in FIG. 3 bear the reference A for the rod outlet from the cylinder VI, B for the rod retraction from this same cylinder, C and D respectively for the rod exit and retraction from the cylinder V2, and E and F respectively for the exit and the return of the telescopic element.

The distributor is associated with micro-contacts making it possible to detect the movement or movements in progress, two micro-contacts being provided for each movement of the cylinders V1 and V2 ensuring the pivoting of the arms. These micro-contacts are referenced al, a2, ... d1, d2. A micro-contact is provided to detect each movement
E and F, these micro-contacts being referenced respectively e and f.

The micro-contacts a1, bl, cl, di, are grouped in the same assembly to form a power relay Rc abcd of the PNS solenoid valve.

 As shown in the drawing, the micro-contacts al and dl on the one hand, and b1 and ci on the other hand, are mounted in parallel so that, during the execution of a cross movement at the level of the cylinders V1 and V2, the EVS solenoid valve is not supplied.

In the live position, and without reaching the first pressure threshold, EVS is supplied by the line RDT2 and RD2Tl, which is closed as well as by the relay Rc abcd which is closed insofar as there is no cross movement AD , BC
When the safety is reached by reaching the first threshold, the pressure gauge 10 or 12 opens the contact 51 and de-energizes the relay RD which, after delay, will close RDTI, close RD1, open RD2, and open RDT2 after delay, the RDT2 time delay being equal to that of RDT1.

 The EVS solenoid valve is no longer supplied and the system is under safety.

Insofar as the operator performs a deteriorating movement, the contact 51 closes and replenishes the relay RD, which will open the contacts RDI and RDT1 and de-energize the relay RD2. Contact RD2 closes immediately, RD2T2 is kept closed during its time delay and the memory relays RAZRACM, RAZRABDM and
RAZREM are powered.

 The RDT2 contact closes immediately. The RD2 relay being de-energized, the RD2T1 contact will close after time delay and supply EVS. The system is primed again.

 The three relays RAZRACM, RAZRBDM, RAZREM in question, are the memory erasure relays of the relays RACM, RBDM and REM. The memories of these three relays are intended to record and keep in permanent information the movement which caused the system to fail by reaching the first threshold. The erasure of the memory will only be obtained when RD is again energized, that is to say when the contact 51 is closed, the pressure having returned to below a critical value.

The erasing relays of RAZRBDM memories and
RAZREM can also be supplied by the RSI1 contact, when using the second pressure threshold, the operation of which is explained below.

When performing a movement, A or C or A and C, that is, lifting, there can be several possibilities:
- The load is admissible therefore RD is supplied. The micro-contacts ai and / or cl are closed, a2 and / or c2, are open. Line A2 not being energized, closing al, ci does not modify the system in any way and EVS is normally supplied. The operation is possible. If an attempt is made to make movements B or D at the same time, the relay Rc abcd opens, the contacts a2, b2 open and de-energize EVS. All movements are impossible, although the pressure value is below the first threshold.

- The load is inadmissible at the start of the movement or becomes so during operation. At the time of the appearance of the fault, after delay, the line A2 is supplied, the micro-contacts ai and / or these are closed.

REM3 and RE3 are closed, and RBDM2 is closed since the fault did not appear by a movement B D, therefore not memorized in RBDM. The RACM relay stores the appearance of the fault on A or C, the RAC relay is supplied. By the fault, RDT2 opens, EVS is de-supplied and the continuation of the operation is no longer possible. If the AC movement is reproduced, there is no EVS recharge, RACM3 being open.

 we must then consider the hypotheses of execution of movements E, F or B, D.

- If an attempt is made to execute E, the microswitch RE3 will open since the RE relay is energized and has no effect on the supply of EVS. The contact being closed on the supply of e, the relay RE being supplied, the contacts RBDM and RBD are closed, RACM4 is open, since RACM has in memory the fault observed on AC, and REM is not supplied The contacts RE1 and RE2, normally closed, are then open. EVS cannot be replenished and the system remains secure.

 - If an attempt is made to execute F, contact f is closed.

Line A2 is energized, the RBD1 and RACI contacts are normally closed since no movement is made on B, D or A, C. Only RACM keeps in memory the appearance of the fault on AC. EVS is replenished for the duration of the operation and until it is interrupted or until contact 51 closes. It is possible to perform movements B, D together with F, while the joint execution of A, C opens the RACI contact and prohibits the movement. This alternative is compulsory because we do not know hydraulically what will be the priority movement and because A, C is aggravating.

 - If we try to execute B, D, the contacts b1, dl will close. The RACM2 contact is open since RACM has in memory the appearance of the fault on A, C. RBDM and RBD cannot be supplied. The RACMi contact is closed as well as the RE1 contact. The EVS solenoid valve will be replenished and movements B, D will be made possible.

Combination with E is impossible because, in this case, contact RE1 would be open.

- If lton tries to execute cross movements,
B, D and A, C, B, D could power up EVS, but the Rc abcd crossing relay opens and leaves the system safe.

- When executing a movement, B, D or BD the two preceding hypotheses are to be considered and the system reacts in each case in the same way, but with the RBD and RBDM control relays.

 - Fault by executing movement F is excluded, because this movement is always deteriorating if it is executed alone.

- When explaining movement A, C, it was
Indicated that the simultaneous execution of destructive movements B, D with F remains possible, but that the combination of F with the movement that created the fault becomes impossible.

 - Fault by executing movement E. The system is designed so that the effects of movement E are assimilated to those of movement B, D. It would also be possible to adopt the opposite possibility and assimilate them to A, C. Due to the hypothesis posed, the default during the execution of a movement E will make it impossible to recharge by movement B, D.

 fl is reminded that E is impossible when a dangerous threshold has been reached either by B, D, or by A, C.

The assimilation of B, D a E is necessary so that, when we descend a load whose point of application is located above the planes H1 and H2 and that the first pressure threshold is reached by execution of the movement
E the continuation of the descent by B, D is prohibited.

 Obviously, the climb by movements A, C remains authorized.

Several hypotheses are to be considered
- Movement E is undertaken and its execution does not have the effect of crossing the first pressure threshold. Contact e will close. However, line A2 is not supplied and EVS remains supplied, so that the movement is executed normally. The EBD movements and
EAC are still possible, only an EBC or EAD crossover will de-energize EVS by opening the crossover relay
Rc abcd.

- The fault occurs when the point of application of the load P is located above the planes III and 112. The contact e closes, the line A2 is energized after opening of the contact 51. The contact RE3 prohibiting the flAC crossing, the RE and REM relays are supplied, and RBDM, RBD and RACM4 are firm since there is no fault on AC or BD, The RE relay opens the RE2 and RE1 contacts, the Rt relay opens the REM2 contact , activating the second pressure threshold detects, and the RME3 contact opens while RMEI closes. No movement is therefore possible if movement E is not interrupted. When E is interrupted, movement F is possible, RBD1 and RAC1 being firm. Although RE1 is closed, movements B-, D are impossible because RACM1 is open for non-fault on A, t.

Movements A, C are possible since, RE3, a, c,
RME1 and RE2 are closed. The supply of EVS takes place and AC which, kinematically is deteriorating, does not allow the contact 52 to open.

- If the point of application of the load P is below the two horizontal planes H1 and H2, the operation of the system is the same with the commissioning of the second pressure threshold, prohibition of movements B, D, and authorization of A, C. The movement A, C, takes effect, 8 but its execution is aggravating and the pressure value detected will reach the second threshold. Contact 52 opens, RS1 is no longer supplied and will close the contact
RST1 which will supply the memory clearing relays
RAZRBDM and RAZREM and simultaneously supply the relays
RAC and RACM of AC movements. The memories RBDM and REM being erased, RBDM1 and REM1 are open, a fault in memory on RACM and RACMi closed. Movements B, D revive EVS well if we do not cross them with E.

 It goes without saying that the invention is not limited to the sole embodiment of the circuit, described above by way of example; on the contrary, it embraces all of its variant embodiments.

Claims (5)

 - CLAIMS  1. - Safety system for a hydraulically controlled lifting device, of the type comprising, associated with each jack (V1) (V2) allowing the angular variation of two arms (2) and (3) and (3) and (2) , a pressure detection device (10, 12) comprising two thresholds, the one of which detects the highest pressure corresponds to the admissible limit pressure, as well as devices for detecting the direction of actuation of each control of the distributor, characterized in that that the information provided by the pressure detection devices control a solenoid valve (EVS) mounted on the safety circuit of the hydraulic system.  2. - Security system according to claim 1, characterized in that the electric circuit with which it is equipped comprises a first line (A1) of electrical supply which, under normal operating conditions, ensures the supply of the device (51) for detecting the first and second pressure thresholds, and a second power supply line (A2) ensuring, after reaching the first threshold, the supply of a block which detects the movements carried out, which gives the orders to prohibit pursuit aggravating movements, which memorizes the movement which created the fault and which re-authorizes the priming of the hydraulic system when the movements carried out are aggravating. 3. - Security system according to claim li characterized in that the security block is arranged so that, insofar as a deteriorating movement is exerted temporarily, it keeps in memory the movement that created the fault and that , insofar as the deteriorating movement is exerted long enough to reduce the pressure below the first threshold, it erases the memories, cuts the supply by the second line (A2), and resumes the '' supply of the solenoid valve (EVS) by the first line (AI). 4. - Security system according to any one of claims 2 and 3, characterized in that, upon reaching the second threshold, there is an inversion of the memories, by erasing the information corresponding to the movement having caused reaching the first threshold and simultaneously memorizing the fault causing the second threshold to be reached, thereby authorizing reverse movements to those having made it possible to reach the second threshold. 5 - Security system according to any one of claims 1 to 4, characterized in that, on the electrical supply line of the device for detecting the first pressure threshold, is mounted a relay (Rc abcd) supplied according to the state of the system either by the first line (Ai) or by the second line (A2), and comprising a contact (a1, bi, ci, di) associated with each control of the distributor corresponding to the articulation cylinders, the corresponding contacts to crossed movements of two cylinders (Vi1 V2) being mounted in parallel.