Power plants – Pressure fluid source and motor – With control means for structure storing work driving energy
Reexamination Certificate
1999-07-07
2001-11-27
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
06321534
ABSTRACT:
TECHNICAL FIELD
This invention relates generally to a ride control system for a machine, and more particularly, to a simple ride control system operable for maintaining a load in a raised position when actuated.
BACKGROUND ART
It is well known that when a machine, such as, for example, a wheel loader, is being driven for a distance with a loaded bucket, there is always the possibility that the machine will be subjected to shocks due to the weight of the loaded bucket reacting to the machine encountering bumps or other obstacles in its pathway. In order to help reduce or eliminate shocks, it is known to use accumulators that are selectively connected to the lift cylinder actuator. These accumulators, when connected to the loaded end of the actuators, serve to absorb the pressure fluctuations in the actuators thus offsetting the changing forces that would otherwise be acting on the various components of the machine. It is these changing forces acting on the machine that produces the shocks. In order to maintain a pre-charge in the accumulator equal to the pressure in the loaded end of the actuator, it is known to connect the accumulator, during normal use, to the loaded end of the lift cylinder actuator. This is normally accomplished by connecting a conduit therebetween. The conduit normally has an orifice therein that is selectively disposed in the conduit when the machine is not operating in the ride control mode. When the ride control system is active, the load supporting end of the cylinder is in free communication with the accumulator in order to absorb the changing forces.
Known systems providing ride control are often complex and give the actuator a spongy feeling. Also, with some of the known systems a slight load drop can occur upon activation of the ride control system.
Accordingly, the present invention is directed to overcoming one or more of the problems as set forth above.
DISCLOSURE OF THE INVENTION
In one aspect of the present invention, a simplified ride control system is provided for use in a fluid system of a machine to cushion the ride of the machine, the machine having a frame with an actuator arrangement disposed between the frame and a load to raise the load relative to the frame, the actuator arrangement having a raise port and being operative in a raise mode to raise the load to a desired height in response to pressurized fluid being directed to the raise port from a source of the pressurized fluid, the ride control system including an accumulator arrangement, and a valve arrangement connected between the accumulator arrangement, the actuator arrangement, and the source of pressurized fluid, and operative to selectively connect the accumulator arrangement to the raise port of the actuator arrangement when in the raise mode while maintaining the load at the desired height. In one preferred aspect of the invention, equalization of pressure in the raise port and accumulator arrangement is maintained prior to activating the ride control.
REFERENCES:
patent: 5147172 (1992-09-01), Hosseini
patent: 5520499 (1996-05-01), Ufheil et al.
patent: 5706657 (1998-01-01), Amborski et al.
patent: 5733095 (1998-03-01), Palmer et al.
Application Serial No. 08/631,698 filed Apr. 12, 1996, entitled “Variable Rate Ride Control System”.
Application Serial No. 09/110,493, filed Jul. 6, 1998, entitled “Variable Rate Ride Control”.
A'Hearn Michael A.
Hajek, Jr. Thomas J.
Hudson Michael D.
Schexnayder Lawrence F.
Tolappa Srikrishnan T.
Caterpillar Inc.
Hanley Steven M.
Haverstock Garrett & Roberts
Leslie Michael
Look Edward K.
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