Patent Application
20070180821
The invention can be classified as belonging to the heavy construction machinery field especially machinery that is made for loading and for lifting.
The invention mainly targets the hydraulic circuit architecture of machines that allow optimal performance while in the loading mode of the machine for the purposes of leveling while maintaining a high-level of safety when it is in a lifting mode.
Generally, certain heavy construction machines are used to fulfill various functions by means of reconfiguring the work equipment. In fact, a traditional work machine, which has one or more arms, could have an attachment for a particular function fixed to its arm. Therefore, a bucket is generally used as a loader as it allows the loading of earth or other material to be transported and unloaded at another destination.
A loader is specifically used during leveling operations. In this case, the movement of the arm in relation to the chassis is left floating so that the bucket can move by scraping the ground and by evenly piling the mound of earth on which it rests. To free up the position of the bucket, usually the two piston chambers that control the direction are engaged. Thus, the machine works on what is known as a “floating” mode of command.
In practice, this “floating” command is obtained by reconfiguration of the hydraulic circuit achieved by the movement of manipulator controls in a particular position. Therefore, in a classic manner, the manipulator has a mobile inclined lever that will deliver variable pressure control based on this inclination. The “floating” position is normally found at the end of the manipulator stroke, which allows the generation of excess pressure in the control circuit. This excess pressure leads to the movement of the slide valves of the main distributor in such a way that the two piston chambers that are engaged become connected.
Furthermore, this same type of machine could also be used for lifting work. In that case, the tool that is attached to the working arm extremity is adapted for this kind of work and, for example, could be a pallet forklift or any other lifting mechanism. Then the hydraulic circuit of the piston chambers is generally equipped with valves known as “safety valves,” used to insulate the piston chamber undergoing consecutive pressure from the weight of the load lifted.
In fact, in case there is a rupture in the piping of the hydraulic circuit it is important to be able to prevent this chamber from emptying too rapidly, which would cause the load to fall.
A safety problem could arise for machines which work in both loading and lifting modes. In fact, when it is in lifting mode, if an operator inadvertently moves the manipulator into the position known as the floating position while the two piston chambers are connected, the load will fall on the ground. This situation is unacceptable for obvious safety reasons.
For this reason, it was proposed that the floating control position for machines that work as both loaders and lifters should be eliminated.
At the same time, we think that this radical solution limits the performance of the machines mainly in leveling operations.
One of the objectives of the invention is to be able to combine the possibility of a floating position for use in loading with a high level of safety.
The invention concerns a heavy construction machine, which acts in known ways as follows:
work equipment including one or more articulated arms in relation to the machine's chassis;
a unit of at least one hydraulic jack for the movement of the work equipment in relation to the chassis; and
a hydraulic circuit feeding these jacks based on the control commands given by a hydraulic manipulator.
This machine is multi-functional, that is, it is able to work in two different modes. Therfore, it can ensure lifting as well as loading functions. In the latter case, the stroke of the jack causing the movement of the machine in relation to the chassis could be made free when the manipulator is placed in a particular position corresponding to the “floating” command.
According to the invention, the machine is characterized by the fact that it has the means to make the floating command of the manipulator inactive when the machine is in the lifting mode.
In other words, the invention prevents the command to move to the “floating” position while the engine works in the lifting mode.
Thus, the invention can prevent the machine from inadvertently going into a floating position, which, in turn, would have caused the load to fall. The safety of the machine is, therefore, ensured in the lifting mode and performance remains high as the leveling operations are still allowed with a floating bucket.
In a particular mode of operation, the movement of the manipulator into the floating command position generates excess pressure in the control portion of the hydraulic circuit. In this case, while the machine is working in lift mode, a pressure reducer inserted into the circuit is activated to limit or even eliminate the effect of this excess pressure. Therefore, even if the operator places the manipulator in the floating position, the corresponding excess pressure is not taken into account by the hydraulic power circuit.
In practice, a diverter valve could be placed parallel to the pressure reducer in order to by-pass the reducer when it should not be working. Thus, when the machine is working in loading mode, the pressure reducer is by-passed so that the excess pressure generated by the manipulator in the floating command is effectively transmitted to the rest of the hydraulic circuit. However, when the machine is working in lifting mode, the regulating valve is blocked in such a way that the pressure reducer does its job and thus blocks the excess pressure generated by the manipulator in case the operator inadvertently places the manipulator in the floating command position.
Advantageous in practice, the configuration of the hydraulic circuit in lifting mode or loading mode can be done by a manual selector, which commands the diverter valve located parallel to the reducer.
The manner in which the invention is made and the advantages resulting from it will be clear from the production description which is given below, with the help of an example and figures attached hereto as follows:
As mentioned earlier, the invention pertains to a heavy construction machine able to work in two different modes. The machine (1), shown in the diagram in
In practice, the bucket (5) could be replaced by a pallet forklift (15) as illustrated in
Classically, the machine can work in loading mode by using a special function called the “floating command”. In this case, the lifting jack (7) does not exert force on the arm (6) and the position of the arm is thus free in relation to its articulation and the chassis (2). This position, known as the “floating” position, is obtained by putting the hydraulic manipulator in a specific position. Specifically, and as illustrated in
This variation in the inclination is obtained when the lever (20) inclines between two limited positions (21, 22). In this case, the inclination of the manipulator allows, as illustrated in
Beyond the position that is generally the front limit position (22), the manipulator moves into the position known as the “floating command” when its inclination reaches a farther position (23).
In this case, additional pressure, typically around 27 bars is delivered to the distributor (27). In that case, the fourth slide valve (31) connects the two chambers (32, 33) of the lifting jack (7), which makes the arm float.
It is noted in
In accordance with the invention the excess pressure generated by the over stroke of the manipulator (20) to bring the bucket to a floating position is eliminated when the machine works in the lifting mode. Thus, when the operator places his machine in lifting mode using an appropriate selector available in the cab, the hydraulic circuit is consequently reconfigured. More specifically, as shown in
On the other hand, in the loading mode a by-pass valve (41) is activated in such a way that it shunts the reducer (40) and therefore allows the eventual excess pressure delivered by the manipulator in a floating position to act appropriately on the distributor (31). This by-pass valve (41) is rendered inactive when the selector indicates a lifting mode function.
A non-return valve (42) can be placed in combination with an electrovalve (43) to allow the blocking of the safety valve during the movement of the manipulator (20) in the direction of the arm's descent or when the machine is fitted with hydraulic suspension of work equipment.
Based on the above, it is clear that the machine made according to the invention allows work with a floating bucket in a loading mode while at the same time ensuring maximum safty in the lifting mode, since in the latter case, the floating position is neutralized.
| Number | Date | Country | Kind |
|---|---|---|---|
| 0351076 | Dec 2003 | FR | national |
The present application is a continuation patent application of International Application No. PCT/FR2004/050672 filed 9 Dec. 2004 which claims priority to French Patent Application No. 0351076 filed 16 Dec. 2003. Said applications are expressly incorporated herein by reference in their entirety.
| Number | Date | Country | |
|---|---|---|---|
| Parent | PCT/FR04/50672 | Dec 2004 | US |
| Child | 11424771 | Jun 2006 | US |
