ELECTRO-HYDRAULIC PRESSURE CONTROL FAN DRIVE SYSTEM WITH ELECTRICAL FAILURE MODE OPERATION
First Claim
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1. A hydraulically controlled fan drive system comprising:
- a housing assembly containing a hydraulic fluid within a fluid reservoir; and
an engaging circuit coupled to said housing assembly and comprising a first pitot tube coupled within said housing assembly and receiving at least a portion of said hydraulic fluid from said fluid reservoir, said portion of said hydraulic fluid defining a fluid pressure within said first pitot tube;
said engaging circuit engaging said housing assembly to a fan shaft in response to said fluid pressure within said first pitot tube; and
a control circuit for controlling said fluid pressure within said first pitot tube, said control circuit comprising a main controller electrically coupled to a relief valve assembly, said control circuit providing selective continuously variable control of said pressure within said first pitot tube and where upon an electric failure, said pitot tube pressure is mechanically modulated to a mid-pressure failure mode.
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Abstract
A fan drive system is provided that is hydraulically controlled having an electrical failure mode wherein midrange operation of the fan drive system is maintained. Accordingly, in the failure mode, a fan drive system hydraulic relief valve is not closed thereby ensuring a degree of operation of the fan drive system even during periods of electrical failure.
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Citations
12 Claims
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1. A hydraulically controlled fan drive system comprising:
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a housing assembly containing a hydraulic fluid within a fluid reservoir; and
an engaging circuit coupled to said housing assembly and comprising a first pitot tube coupled within said housing assembly and receiving at least a portion of said hydraulic fluid from said fluid reservoir, said portion of said hydraulic fluid defining a fluid pressure within said first pitot tube;said engaging circuit engaging said housing assembly to a fan shaft in response to said fluid pressure within said first pitot tube; and a control circuit for controlling said fluid pressure within said first pitot tube, said control circuit comprising a main controller electrically coupled to a relief valve assembly, said control circuit providing selective continuously variable control of said pressure within said first pitot tube and where upon an electric failure, said pitot tube pressure is mechanically modulated to a mid-pressure failure mode. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11)
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12. A hydraulically controlled fan drive system comprising:
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a housing assembly containing a hydraulic fluid; a pulley connected to said housing assembly for turning said housing assembly; a fan shaft rotatably mounted to said housing by a hydraulically actuated clutch; a piston slidably mounted with a piston housing for actuating said clutch; a stationary pressure tube for delivering hydraulic fluid pressure within said housing assembly to said piston housing; a relief valve for controlling the fluid pressure within said piston housing by selectively connecting said piston housing with a sump; and a controller having bi-directional electrically powered actuation for positioning said relief valve, said controller having mechanical springs to modulate said relief valve upon electrical failure.
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Specification