EP0943738B1 - Hydraulic interlock system for a loader tool - Google Patents

Description

The present invention relates to a hydraulic locking system able to lock a tool on the tool holder frame of a front loader, including lifting the stretcher is controlled by a hydraulic jack, called a lifting cylinder.

Besides the traditional mechanical locking systems of the tool, there systems exist using a specific hydraulic cylinder. They have the advantage that unlocking, for tool change, can be easily achieved by the operator assigned to the loader control. However, they pose the risk of untimely unlocks and, correspondingly, unexpected tool stalls, which may occur as a result of a false maneuver and / or by persons not authorized.

In this regard, it happens quite frequently that the unlocking takes place. while the tool is at rest, placed on the ground. In this position the tool is not easily visible to the operator, who is in the tractor cabin, and is not necessarily warned and aware of the release of the tool. Subsequent maneuvers can then cause damage to the tool holder, or even to the tool left on the ground and not visible.

It can also happen that the tool comes off while the stretcher is in the high position, which poses a safety problem for people susceptible be present near the charger.

A hydraulic locking system for an excavator is disclosed in document US-A-5727342. Unlocking this shovel is only possible in a specific position and is exerted by a single acting cylinder.

The invention aims to solve these problems, for a front loader.

To this end, the system which is the subject of the present invention comprises at least minus a lock, another hydraulic cylinder - called lock - and a solenoid valve, these elements being able to be mounted on said charger, said lock being controlled by said locking cylinder, which is capable of being supplied with hydraulic fluid during use, via said solenoid valve, from the cylinder pressure chamber lifting, so that unlocking of the tool is only possible if the pressure hydraulic system in this pressure chamber exceeds a threshold value predetermined. It includes a pair of coaxial locks which are movable in translation, in opposite directions, and are secured respectively to the rod and to the cylinder of the actuator locking.

Thanks to this arrangement, when the tool is placed on the ground and - correlatively - the pressure chamber of the lifting cylinder is subjected to pressure low, lower than this threshold value, the risk of the tool stalling is eliminated.

il comporte un système élastique qui sollicite les verrous dans le sens du verrouillage, à l'encontre de la pression hydraulique du vérin de verrouillage ;

- le vérin est à double-effet et la pression différentielle dans ses deux chambres tend à le maintenir en extension, dans le sens du verrouillage.

According to preferred embodiments of this system:

it includes an elastic system which biases the latches in the locking direction, against the hydraulic pressure of the locking cylinder;

- The cylinder is double-acting and the differential pressure in its two chambers tends to keep it in extension, in the locking direction.

Advantageously, said solenoid valve is electrically controlled by means of a push button embedded in the wall of a control handle, this which makes it difficult to access.

There is therefore a risk of unintentional unlocking further reduced.

Finally, according to a possible additional characteristic, the system includes a stretcher tilt sensor electrically connected to said solenoid valve so as to prohibit the control of the locking cylinder in the event of tilting excessive.

This arrangement eliminates the risk of the tool stalling when it found in high position.

Other characteristics and advantages of the invention will become apparent from the description and attached drawings, which represent, by way of non-limiting example of the invention, a preferred embodiment.

• la figure 1 est un schéma général représentatif de l'ensemble du système, appliqué à un chargeur monté sur un tracteur agricole, outil enlevé ;
• les figures 2, 3 et 4 sont des schémas similaires à la figure 1, avec l'outil en place, qui montrent des positions différentes du brancard, respectivement en position basse (de repos) (figure 2), en position légèrement relevée (figure 3), et en position haute (figure 4).

In these drawings:

• Figure 1 is a general diagram representative of the entire system, applied to a loader mounted on an agricultural tractor, tool removed;
• Figures 2, 3 and 4 are diagrams similar to Figure 1, with the tool in place, which show different positions of the stretcher, respectively in the low (rest) position (Figure 2), in the slightly raised position (Figure 3), and in the high position (Figure 4).

In the figures, an agricultural tractor equipped with the reference T has been designated a front loader C comprising, in the usual manner, an articulated stretcher B provided with its front end of a tool holder frame 2.

The loader has a pair of lifting cylinders 1 (only one of which is visible in the front view corresponding to the diagram), which make it possible to pivot the stretcher B around its axis of articulation X to cause lifting or lowering of the tool carried by the frame 2.

The tool is not shown in Figure 1. In the following figures, it is a bucket, designated O.

It also includes a VB tipping cylinder allowing the tool to pivot relative to the stretcher.

In the illustrated embodiment, the lifting cylinder 1 is double-acting. It comprises a piston 10 secured to the frame of the loader, and a cylinder 11 secured to the stretcher B.

In the diagrams, the conduits of hydraulic fluid in strong solid lines, and electric cables in thin solid lines.

Usually, the tractor T is equipped with low and high pressure hydraulic sources, respectively BP (atmospheric pressure) and HP (pressure of the order of 15.10 ⁷ to 2.10 ⁷ Pa).

Line 8 corresponds to the supply of high pressure liquid, and line 9 when returning to the tank (low pressure line). The conduits 8, 9 are connected, via a three-position control valve 5, on the one hand to the small chamber 101 (side of the piston rod 10) of the jack 1, on the other hand to its large chamber 100. This will be conventionally designated in the following description and in the claims "pressure chamber". It is, in fact, the bringing of the pressurized liquid into this chamber 100 which causes the extension of the jack and the lifting of the tool.

When the hydraulic fluid is trapped in this chamber (closed dispenser), unless the tool rests on the ground, the weight of the stretcher and the tool tends to bring them down, generating a high pressure in the chamber 100.

The connections between the distributor 5 and the chambers 100 and 101 are referenced respectively 80-80 'and 90.

In the illustrated state of the distributor (neutral position) these chambers are isolated, the liquid cannot escape or penetrate it.

The tool holder frame 2, which is shown even from the side on the right of the figures, comprises in the upper part, two semi-cylindrical housings 21 in which can engage appropriate pins provided on the tool.

Its locking is achieved, in a well known manner, by a pair of latches in the form of horizontal, coaxial rods 32, 33. They are carried by a jack hydraulic 3, arranged transversely, the cylinder of which is designated 31 and the piston 30. One 32 of the locking rods is fixed in the extension of the piston rod 30, and the other 33 on the back of the cylinder 31. A pair of coil springs 20 is constantly tensioning pushing the locks 32, 33 outwards, which corresponds to the extension of the cylinder 3, in a locked position. In this position, the free end portions locks engage in appropriate receiving openings provided on the tool. We have designated by the references 300, 301, respectively, the large room and the small cylinder chamber (piston rod side) 3.

It is the force of the springs 20 which determines the pressure threshold value authorizing unlocking.

To unlock the tool, high pressure liquid is brought into the small chamber 301 of the jack, while the large chamber is connected to the reservoir R (low pressure), which causes the jack to retract, and the retracting locks. Of course, the value of the high pressure is sufficient to overcome the force of the springs 20.

The jack 3 is controlled by a control solenoid valve 6, with two positions.

In the position shown in Figures 1 and 4, the chamber 301 communicates with low pressure via conduits 81, 83. In the position shown in Figures 2 and 3, it communicates with the aforementioned line 80 '(connected to the chamber pressure cylinder 100).

The large chamber 300 of the jack 3 is permanently connected, by a conduit 82, to the reservoir. It is therefore always subjected to low pressure.

The solenoid valve 6 is controlled by an electric switch 700, itself actuated by a push button 70.

The large-scale detail that appears in a circle at the top left of the Figure 1 shows a part of the control handle 7 which is provided with the tractor. AT using this handle, which has other push buttons 71, 72, it is possible to actuate the various loader operating devices, and in particular its jacks.

According to an interesting characteristic of the mode of implementation of the invention here illustrated, the push button 70 is embedded in the handle 7. Thus, its support face of the finger is located at a level lower than the surface of the handle, which makes access difficult; the risk of it being pressed inadvertently is therefore practically zero. To press it, it is necessary, using your finger, to aim the opening in which it is embedded, which supposes a conscious and voluntary action on the part of the operator.

On the stretcher B is fixed a tilt sensor 4 of the known type. It is for example a mercury level switch, connected to the supply circuit of the solenoid valve 6. It is adjusted so that the circuit is closed when the height H ₁ of the tool relative to the ground S is less than a determined height H ₀ (situation illustrated in Figure 3), and open when this height H ₂ is greater than H ₀ (Figure 4).

The value of the threshold height H ₀ is preferably of the order of 1.50 m, less than the average height of a person.

The operation of the system will now be explained.

In working situation, the switch 700 is in the open state, which is its natural state.

The solenoid valve 6 is in the state of FIG. 1, so that the two chambers 300, 301 of the jack 3 are connected to the tank R and are at the bottom. pressure. The tool O is kept locked on the frame 2 by means of the two locks 32, 33 which are subjected to the sole action of the springs 20.

It should be noted that in the event of overpressure in the tank, the cylinder is subjected to differential pressure, corresponding to a higher force in the large room 300 only in the small room 301 (due to the different sections).

The cylinder is therefore requested in extension, in the locking direction, this which eliminates the risk of accidental unlocking.

When the tool is placed on the ground, situation illustrated in Figure 2 (position rest), it is the soil S which absorbs the weight of the tool (and of the stretcher).

The pressure in the chamber 100 of the lifting cylinder 1 is therefore low.

If the operator wants to unlock, he presses the button 70 to close the switch 700, so as to control the change of state of the solenoid valve 6.

The chamber 301 of the unlocking cylinder 3 is thus placed in communication, via conduits 81 and 80 ', with chamber 100. However, the latter being under low insufficient pressure to overcome the springs 20, the jack 3 remains in extension, and the unlocking cannot take place.

The objective recalled in the preamble of this description, namely make it impossible to unlock it when the tool is placed on the ground, is therefore reached.

If the tool is raised from the ground, at a height H ₁ less than H ₀ - situation illustrated in FIG. 3 - there is a high pressure in the chamber 100, due to the weight of the stretcher and the tool. This pressure is then sufficient to cause unlocking, the latches retracting inwards as a result of the retraction of the jack 3 (arrows f , FIG. 3).

Stalling the tool does not pose a safety problem, due to the low height H ₁ .

If, on the other hand, the tool is raised from the ground to a height H ₂ greater than H ₀ (FIG. 4), the tilt sensor 4 comes into action, keeping the supply circuit of the solenoid valve 6 open. It therefore remains in its natural state, in which the chamber 301 of the locking cylinder is subjected to low pressure. Unlocking is impossible. Thus, there is no risk of accident which could result from the presence of a person under the tool O at the time of its stall.

Claims (5)

1. A hydraulic locking system suitable for locking a tool (O) on the tool-carrier frame (2) of a loader whose boom (B) is lifted under the control of a "lift" hydraulic actuator (1 ), said locking system comprising at least one bolt (32, 33), another hydraulic actuator (3) referred to as a "locking" actuator, and a solenoid valve (6), these elements being suitable for mounting on said loader, said bolt (32, 33) being controlled by said locking actuator (3) which is suitable, while in use, for being fed with hydraulic liquid via said solenoid valve (6) from the pressure chamber (100) of the lift actuator (1 ) in such a manner that it is not possible to unlock the tool (O) unless the hydraulic pressure in said pressure chamber (100) exceeds a predetermined threshold value, the system being characterized by the fact that it comprises a pair of bolts (32, 33) on the same axis that are mounted to move in translation in opposite directions, and that are secured respectively to the rod (30) and to the cylinder (31) of the locking actuator (3).
2. A system according to claim 1, characterized by the fact that it includes a resilient system (20) urging the bolts (32, 33) in the locking direction against the hydraulic pressure of the locking actuator (3).
3. A system according to claim 1 or claim 2, characterized by the facts that said locking actuator (3) is a double-acting actuator, and that pressure differential in its two chambers (300, 301) tends to keep it extended in the locking direction.
4. A system according to any one of claims 1 to 3, characterized by the facts that said solenoid valve (6) is electrically controlled by means of a pushbutton (70) sunk in the wall of a control lever (7), thereby making it difficult to access.
5. A system according to any one of claims 1 to 4, characterized by the fact that it includes a sensor (4) for sending the angle of inclination of the boom (B) and electrically connected to said solenoid valve (6) in such a manner as to prevent the locking actuator being actuated if the angle of inclination is excessive.

Images