Power plants – Pressure fluid source and motor – With control means for structure storing work driving energy
Reexamination Certificate
2000-02-29
2001-05-01
Ryznic, John (Department: 3745)
Power plants
Pressure fluid source and motor
With control means for structure storing work driving energy
C060S419000
Reexamination Certificate
active
06223529
ABSTRACT:
The invention relates to a hydraulic system in accordance with the preamble of claim
1
.
Such a hydraulic system is described in the not pre-published WO application 9731185 by the same applicant. This application describes a hydraulic transformer in which an oil flow of a first pressure is transformed to an oil flow of a second pressure by means of supplying or discharging a third oil flow of low pressure. Such a hydraulic transformer has proved to be particularly suitable for use with hydromotors which are used in so-called four-quadrant operation. This means that the hydromotors are used in two directions of movement and in two directions of loading so that they accelerate as well as delay in both directions. The added possibility of recovering energy during braking makes the use of such hydraulic transformers very attractive, especially in combination with the fast adjustment facilities of the hydraulic transformer described in WO 9731185.
When the hydromotor is coupled directly to the hydraulic transformer and the load on the motor is reversed and consequently the pressures in the hydraulic transformer are reversed, the application of the known hydraulic transformer in a hydraulic system designed for the above-mentioned four-quadrant operation causes undesirable conditions such as, for instance, cavitation. This occurs if after reversal of the load the motor and consequently also the rotor in the hydraulic transformer keep moving in the same direction due to, for instance, the inertia of the moving mass.
It is the object of the invention to improve these matters and to this end switching means are present for connecting the low-pressure pipe with the first user's port or with the second user's port.
Alternately connecting the low-pressure pipe with either the first user's port or the second user's port prevents the development of negative pressures in the hydraulic transformer, thereby avoiding cavitation.
In accordance with an improvement of the invention the operation of the switching means is coupled with the operation of the adjustment device. The fact that the load of the hydromotor is produced by the alteration of the pressure ratio between the high-pressure connection, the first user's port and the second user's port, and thus as a result of the adjustment of the adjustment device, and the fact that simultaneously also another flow through the hydraulic transformer has to take place, allows the switching means and the adjustment device to be coupled, whereas facilitating operation.
In accordance with one embodiment the switching means comprise valves which form part of the adjustment device. The incorporation of the valves in the adjustment device makes operating simple. This embodiment may be employed, for instance, if the adjustment device can be operated manually.
In accordance with another embodiment the switching means comprise valves that are operated by means of a lever, which lever is coupled with the adjustment device. By coupling the valves with the adjustment device by means of a lever a simple manner of operation is obtained. This embodiment may be employed, for instance, if the adjustment device can be operated manually.
In accordance with another embodiment the switching means comprise hydraulically operated valves which are activated by the pressure of the first user's port and the second user's port. This means that the construction may be simple because simply operated valves can be used such as, for instance, pressure-controlled non-return valves.
In accordance with another embodiment the switching means comprise electrically operated valves. Using electrically operated valves involves that they can be placed at various locations in the device to be driven.
The invention also relates to the known hydraulic system described earlier, where a stop valve is provided in one of the connecting pipes, between the hydraulic transformer and the hydromotor. Such a stop valve is necessary in order to prevent the hydromotor from moving under the influence of a load. When the setting of the adjustment device is such that the oil supply from the high-pressure pipe is zero, and the two connections of the hydromotor have the same pressure, the absence of a stop valve might mean that an external load could cause the rotor in the hydraulic transformer to rotate, which may be undesirable.
In accordance with a further improvement of the invention in which the low-pressure pipe is optionally permanently connected with the first user's port or the second user's port a short-circuiting pipe is provided between the first user's port and the second user's port, optionally provided with a valve. This means that while the hydromotor is at a standstill, the hydraulic transformer's rotor can continue to rotate above a minimum number of revolutions, which is an improvement, since due to the limited number of chambers, the rotation of the hydraulic transformer's rotor can become unstable below a certain minimum number of revolutions.
According to an embodiment of the hydraulic system in accordance with the invention, said embodiment is executed having a hydromotor which is loaded in one direction, with a connecting pipe which is connected with the first user's port provided with a shuttle valve between the high-pressure pipe and the hydraulic transformer and the connecting pipe, and between the hydraulic transformer and the hydromotor. This allows the reversal of the drive's direction of movement, so that the energy released during the movement of the load is returned into the high-pressure pipe, while the rotational direction of the rotor in the hydraulic transformer does not change. As a result the rotor does not need to come to a stop but can continue to rotate at least at the minimum number of revolutions.
In accordance with a further improvement the shuttle valve has a rest position for closing off the connecting pipe while the high-pressure pipe is opened. This simple manner allows the hydromotor to be maintained in a certain position.
REFERENCES:
patent: 3294369 (1966-12-01), Butler
patent: 3627451 (1971-12-01), Kouns
patent: 3838574 (1974-10-01), Gelders
patent: 4077746 (1978-03-01), Renynolds
patent: 4255957 (1981-03-01), Davydov et al.
patent: 4974994 (1990-12-01), Kirstein et al.
patent: 5628188 (1997-05-01), Kordak
patent: 5852933 (1998-12-01), Schmidt
patent: 6116138 (2000-09-01), Achten
patent: 3404534 (1985-09-01), None
patent: 4420704 (1995-12-01), None
patent: WO 9731185 (1997-08-01), None
Innas Free Piston B.V.
Kinney & Lange , P.A.
Ryznic John
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