Hydraulic drive circuit with flow divider and bypass valve

A hydraulic drive with a flow divider and a bypass wherein fluid can either be allowed to flow from a flow divider to hydraulic actuators in parallel or the fluid can be allowed to bypass the flow divider and flow directly to the hydraulic actuators in parallel.

Not applicable

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to a hydraulic circuit using a flow divider as a means of dividing flow in conjunction with a valve means that permits bypassing the flow divider as desired.

2. Background Information

Hydraulic systems are popular in applications involving hazardous, dirty, and nasty environments, such as coal mines, quarries, food processing plants, and construction sites. Much effort has been expended in trying to increase the efficiency and performance ranges of hydraulic drives.

Open loop hydraulic circuits are very common in industrial applications as they are often less expensive than circuits known, in the trade, as closed loop systems which comprise a fixed or variable displacement pump supplied with fluid by means of a charge pump.

Flow dividers are popular for splitting hydraulic fluid flows to actuators such as, but not restricted to, motors and cylinders. Valve type flow dividers are very popular because of low cost. Rotary flow dividers are less common, but often used because of some of their performance advantages.

Any component in a hydraulic system uses some power to operate. It is inherent in the Second Law of Thermodynamics, which can be phrased as: “The house always takes its cut”.

In hydraulic vehicle drives, the desirability of using a flow divider, especially a rotary flow divider, is offset by the pressure drop of fluid flowing through the flow divider as well as friction inherent in a rotary flow divider. Consequently, applicant is unaware of any successful use of a rotary flow divider in conjunction with vehicles with hydraulic drive wheels.

For purposes of definition, the term hydraulic as used in hydraulic drives encompases both closed loop hydrostatic drives as well as open loop hydraulic drives.

As will be seen from the subsequent description, the preferred embodiments of the present invention overcomes these and other shortcomings of existing hydraulic flow dividing technologies.

SUMMARY OF THE INVENTION

The present invention in the preferred embodiment is a flow divider used in conjuntion with a bypass valve so that a hydraulic drive may be operated either with or without the flow divider. This permits the use of the flow divider as needed, and the bypassing of the flow divider to save energy when the flow divider is not required.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIGS. 1 and 2illustrate the preferred embodiment of the present invention, a hydraulic drive circuit1comprising a flow divider3and a bypass means4.

The circuit1further comprises a pump2, actuators6, a junction2A, pressure lines20,21, and22, and return lines30.

In the preferred embodiment, the flow divider3is a gerotor flow divider, such as is available from White Hydraulics, a manufacturer, located in Hopkinsville, Ky. For enablement purposes, for a 40 gallon per minute pump, the White model FD00181800F is an appropriate model.

The flow divider3comprises output ports3A and3B and an inlet port3C.

The bypass means4, in the preferred embodiment, as an enablement disclosure, is a two position, two section, five port valve, with a spring return, known as an SDS selector valve, available from Cross Manufacturing Company, 100 Factory Street, Lewis, Kans. 67552, according to their literature, VSD1 8/87.

The bypass means4, in the preferred embodiment comprises ports A, C, D, E, and F.

The hydraulic circuit1is shown as a closed loop hydrostatic drive circuit with actuators6shown in a series parallel arrangement, i.e. two parallel sets, or rows of three actuators6in series.

Flow from the pump outlet2A splits at the junction20A into pressure lines20and21. The pressure line20is connected to port F of the bypass means4. The pressure line21connects to the flow divider inlet3C of the flow divider3.

Port3A of the flow divider3is connected to port E of the bypass means4. Port3B of the flow divider3is connected to port B of the bypass means4.

FIG. 1shows the bypass means4in the unactivated, normal, at rest mode, wherein the ports A and E of the bypass means4are blocked, meaning no flow is possible from the flow divider3through the pressure lines22through said ports A and E of the bypass means4.

However, fluid does flow through the pressure line20that connects to port F of the bypass means4. As port F is open and connected to ports D and C, fluid passes to the rotary actuators6. When the rotary actuators6power wheels of a vehicle, normally ground contact results in equal flow to each row of rotary actuators6.

The bypass means4can be selected with sufficient flow capacity so as to minimize pressure drops through the bypass means4as compared to flowing through the flow divider3, for normal operation.

However, when there is a problem, such as can be encountered when a vehicle with hydraulic actuators6in a series parallel circuit is climbing a hill at an angle, where flow to each row of actuators6can become unbalanced, the bypass means4can be actuated, (ref.FIG. 2) so that the flow from the ports3A and3B of the flow divider3now flows through the ports E and A, respectively, of the bypass means4, maintaining equal flow to each row of actuators6. The fluid flow from the pressure line20to the port F of the bypass means4is now blocked.

Although the description above contains many specificities, these should not be construed as limiting the scope of the invention but as merely providing illustrations of some of the presently preferred embodiments of this invention.

While gear type rotary flow dividers of high capacity with low pressure drop exist, they tend to be considerably more expensive and less efficient across the lower speed ranges than gerotor flow dividers such as are manufactured by White Hydraulics.

Also, the term fluid is intended to cover any fluid suitable for serving its intended purpose in the preferred embodiment of the invention described. There are many different types of fluids currently used or being developed for hydraulic drives, such as, but not restricted to, hydraulic oils, engine oils, synthetic oils, vegetable base oils, even water with and without additives.

It will be obvious to those skilled in the art that modifications may be made to the embodiments described above without departing from the scope of the present invention. Thus the scope of the invention should be determined by the appended claims in the formal application and their legal equivalents, rather than by the examples given.