Hydraulic fluid contamination monitor

Details Hydraulic fluid contamination monitor Hydraulic fluid contamination monitor

1998-11-16

2001-12-18

Hannaher, Constantine (Department: 2878)

Radiant energy

Invisible radiant energy responsive electric signalling

Infrared responsive

C250S227220

Reexamination Certificate

active

06331704

ABSTRACT:

The present invention is directed to a method and apparatus for detecting suspension of particulate debris in hydraulic fluid systems. More specifically, the invention is directed to a device and method for both detecting the presence of such particles and monitoring an increase in the quantity or density of such particles while the hydraulic fluid is flowing through a hydraulic or other fluid flow line. The invention is particularly useful in that it can be mounted directly on a vehicle, industrial equipment including mobile equipment or specialized power machinery.
Under the present invention, a fluid specification monitor (FSM) is mounted to optically view and monitor the hydraulic fluid as it flows through a fluid flow line of the hydraulic system for example, in the hydraulic return line. The monitor can physically fit into the hydraulic fluid flow line. Under one embodiment, the portion of the fluid flow line being monitored can have the same flow area as the adjacent portions of the fluid flow line so that it will not create an added pressure drop to the system.
In one embodiment, a light emitting diode directs a beam of light through an aperture and then through a beam splitter, so that a sample of the axial light source can be taken by a monitoring photodiode to ascertain the amount of light being emitted by the diode source. The rest of the light is directed along the axial path through the liquid which is flowing as a small column through the fluid flow line. The fluid flow line is provided with windows of glass or a synthetic sapphire material which permit the light beam to pass through the fluid flow line and the hydraulic fluid flowing therethrough. On the opposite side of the fluid flow line is at least one collection lens. A light trap or mask is provided along an axis defined by the light emitting diode and the center of the collection lens in order to block any in-line light directly from the source. The light trap or mask is confined to the central portion of the collection lens lying within a small radius of the in-line axis so that scattered light radially outwardly of the mask will pass through the lens or lenses and will direct the light to a photodiode and amplifier electrically connected thereto. Particles, water and air bubbles, and other contaminants in the fluid will reflect and scatter part of the in-line light beam and this scattered light is to be detected optically. If the contamination level in the hydraulic fluid increases beyond a predetermined level, the photodiode will cause the electrical signal emitted by the amplifier to increase. Upon an increase beyond a predetermined amount, the monitor will set off an alarm to thereby permit the operator to take corrective action before the system is damaged.
The monitoring system of the present invention is not intended to detect or count individual particles but rather indicates the relative amount of light scattered from an aggregate amount of material moving through the oil chamber, as the light passes through the hydraulic fluid flowing through such oil chamber (i.e., a section of the fluid flow line). It is preferred that the monitoring system have digital electronics rather than analog electronics as a digital monitoring system is better able to process the optical signal and to compensate for variations in temperature of the infra-red light emitting diode and photodiode. Although analog circuitry is difficult to compensate for such variations in temperature, it is suitable for many applications.


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