Communications: electrical – Condition responsive indicating system – Specific condition
Reexamination Certificate
2003-04-01
2004-02-24
Trieu, Van (Department: 2636)
Communications: electrical
Condition responsive indicating system
Specific condition
C340S604000, C340S450100
Reexamination Certificate
active
06696960
ABSTRACT:
FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT
None.
BACKGROUND OF THE INVENTION
This invention is related to warning systems, particularly apparatus for quickly signaling when a hydraulic system has sprung a leak.
Many types of equipment use hydraulic systems as the power source for various attachments and for their own component parts. For example, some commercial lawn mowers used to cut the grass on golf course greens use pressurized hydraulic fluid to power the cutting reel and to drive the mower's wheels using individual hydraulic motors at each wheel. One problem with hydraulic systems, which is particularly acute with golf course green lawn mowers, is that if the system springs a leak much damage can be done to the golf green by the hot hydraulic fluid before the operator notices the leak.
There are many types of low fluid level warning systems presently available that can be used to alert the operator of a leak in the system. Such sensors commonly detect when the fluid level drops below a set level. Since hydraulic fluid heats up and expands during use, the reservoir fluid level also rises during use. Therefore the set level must be set at a point below the lowest operating level when the fluid is still cool. If the hydraulic system springs a leak while the hydraulic fluid is cool, the sensor will drop below the set level relatively quickly. However, if the leak occurs after the fluid has heated up and expanded during use, a rather large quantity of hydraulic fluid will be lost before the system provides its warning. With slow or moderate leaks this may or may not be catastrophic for a golf course because the fluid would be spread over a large area. However, if a fast leak occurs on a golf green, a substantial volume of hot hydraulic fluid can be deposited in a relatively small area. This can lead to the destruction of a green, which represents a very expensive loss.
SUMMARY OF THE INVENTION
A first aspect of the present invention is directed to an improved hydraulic system of the type comprising a hydraulic fluid reservoir and a hydraulic circuit assembly comprising lines and hydraulic components. The hydraulic components comprise a hydraulic actuator comprising a cylinder, defining an interior, a reciprocating piston within the interior dividing the interior into first and second regions, and a first shaft extending from the piston, through the first region and out through a first opening in the cylinder. At least two of the hydraulic components and the reservoir are fluidly coupled to one another by lines. Hydraulic leak warning apparatus, fluidly coupled into the hydraulic fluid reservoir, is constructed to provide a signal indicating a possible hydraulic fluid leak. The improvement comprises means for compensating for changes in the volumes of fluid within the first and second regions as the piston moves within the cylinder so that actuation of the hydraulic actuator has no effect on the fluid level within the reservoir. The compensating means may comprise a second shaft extending from the piston, through the second region and out through a second opening in the cylinder, the second shaft being sized so that the total fluid volume within the first and second regions remains constant as the piston moves within the cylinder. The compensating means may also comprise a secondary hydraulic ram comprising a secondary cylinder defining secondary interior, a secondary reciprocating piston within the secondary interior, a secondary shaft extending from the secondary piston and out of the secondary cylinder, and a coupler operably coupling the first shaft and the secondary shaft so that movement of the first shaft causes corresponding movement of the secondary shaft.
A second aspect of the present invention is directed to a method for enhancing the operation of a hydraulic leak warning apparatus by stabilizing the amount of hydraulic fluid within a hydraulic fluid reservoir of a hydraulic system. The hydraulic system is of a type comprising a hydraulic fluid reservoir and a hydraulic circuit assembly comprising lines and hydraulic components. The hydraulic components comprise a hydraulic actuator comprising a cylinder, defining an interior, a reciprocating piston within the interior dividing the interior into first and second regions, and a first shaft extending from the piston, through the first region and out through a first opening in the cylinder. At least two of the hydraulic components and the reservoir are fluidly coupled to one another by lines. Hydraulic leak warning apparatus, fluidly coupled into the hydraulic fluid reservoir, is constructed to provide a signal indicating a possible hydraulic fluid leak. The method comprises compensating for any changes in the volumes of fluid within the first and second regions as the piston moves within the cylinder so that actuation of the hydraulic actuator has no effect on the fluid level within the reservoir. The volume change compensating step may comprise extending a second shaft from the piston, through the second region and out through a second opening in the cylinder and sizing the second shaft to have the same cross-sectional area as the first shaft so that the total fluid volume within the first and second regions remains constant as the piston moves within the cylinder. The volume change compensating step may also comprise coupling a secondary shaft of a secondary hydraulic ram to the first shaft, the secondary hydraulic ram further comprising a secondary cylinder defining secondary interior and a secondary reciprocating piston within the secondary interior, the secondary shaft extending from the secondary piston and out of the secondary cylinder, so that movement of the first shaft causes corresponding movement of the secondary shaft.
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Hann James F.
Haynes Beffel & Wolfeld LLP
Trieu Van
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