Power plants – Pressure fluid source and motor – With control means for structure storing work driving energy
Reexamination Certificate
2000-06-12
2001-08-28
Look, Edward K. (Department: 3745)
Power plants
Pressure fluid source and motor
With control means for structure storing work driving energy
C060S469000
Reexamination Certificate
active
06279316
ABSTRACT:
The present invention relates to a load arm suspension system for a load arm assembly with at least one hydraulic cylinder, which load arm suspension system comprises an accumulator, which is connected to a first cylinder space of the at least one cylinder, and a tank for hydraulic oil, which is connected to a second cylinder space of the at least one cylinder.
A load arm suspension system is used in a machine, such as a wheeled loader, in order to increase the comfort of the driver in the machine and in order to prevent material that is being carried by the load arm assembly galling from the load arm assembly. If, for example, a scoop is arranged on the load arm assembly, it is desirable that the material that is loaded in the scoop does not fall out of the scoop when the machine goes over a bump. A loading machine provided with large tyres uses the tyres as springs on an uneven surface. However, the tyres are not capable of effectively damping the jumping movements and pitching oscillations that occur in the machine body when the machine travels on an uneven surface.
With a load arm suspension system coupled to the cylinders that control the load arm assembly, the load arm assembly becomes movable in relation to the machine body when the latter travels on an uneven surface. The machine body and the load arm assembly can to a greater or lesser extent oscillate in phase opposition and thus counteract the movements of one another. Damping of the oscillations of the load arm assembly takes place by kinetic friction in the load arm assembly and throttling of the hydraulic oil flow between the cylinders and the accumulator in the load arm suspension system.
When the machine goes over a bump in the surface, the machine body moves upwards. On account of the mass inertia in the load assembly, the load assembly tends to stay at its existing level above the surface. Instead of the load assembly following the machine body upwards, the pistons of the cylinders are forced into the cylinders, which means that hydraulic oil flows to the accumulator. The gas present in the accumulator will thus be compressed. The pistons will be displaced into the cylinders as long as the pressure in the cylinders is lower than the pressure that is needed in order to overcome the accelerating force and the force of gravity from the load assembly. When the machine goes over a hole in the surface, the reverse sequence occurs, that is to say that hydraulic oil flows from the accumulator to the cylinders.
During work with the machine in, for example, a gravel pit, the load arm suspension system is deactivated when a scoop mounted on the load arm assembly is to be filled. The machine then drives with great force into a gravel heap, with the scoop located in front of it. It is then desirable that the load arm assembly is rotationally rigid and that the pistons in the cylinders maintain their set position. Subsequently, when the machine is to transport the gravel in the scoop, the load arm suspension system is activated. On activation of the load arm suspension system, the load arm assembly is to maintain its set position.
One problem in known load arm suspension systems is that of maintaining the set position of the load arm assembly when the load arm suspension system is deactivated and when the load arm assembly is acted on by a great external force. Another problem in the known load arm suspension systems is that of maintaining the set position of the load arm assembly when the load arm suspension system is activated.
One object of the present invention is to produce a load arm suspension system of the type indicated in the introduction, which eliminates the abovementioned problems when the load arm suspension system is on the one hand deactivated and on the other hand activated.
According to the invention, this is achieved by virtue of the fact that a first valve member is arranged between the accumulator and the first cylinder space or the at least one cylinder, and that a second valve member is arranged between the tank and the second cylinder space of the at least one cylinder.
By means of the first and second valve members, a machine with such a load arm suspension system allows the set position of the load arm assembly to be maintained on the one hand when the load arm suspension system is deactivated and at the same time acted on by a great external force and on the other hand when the load arm suspension system is activated when the pressure in the accumulator differs from the pressure in the cylinders.
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Kershteyn Igor
Look Edward K.
Volvo Wheel Loaders AB
Young & Thompson
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