Automatic blower control system for inboard marine engines

Claim 1

An automatic blower control system for use in combination with an inboard marine engine having associated therewith an exhaust blower for ventilating the compartment in which said engine is disposed, a power source for said blower, a blower switch coupled between said blower and said power source, and an engine starting circuit including a starter solenoid circuit, said system comprising first switching means having normally open contacts coupled in series with said starter solenoid circuit and having a control input; means coupled between said blower switch and said starter solenoid circuit for providing a voltage proportional to time elapsed from the time said blower switch is closed, a first source of reference d.c. voltage, an operational amplifier having a first input coupled to said first source of reference d.c. voltage, a second input coupled to said means for providing said time proportional voltage, and operating to produce a relatively higher output only when said time proportional voltage exceeds said first reference d.c. voltage whereby said starter solenoid circuit is completed only after the expiration of a predetermined period of time after said blower switch is closed; sensing means associated with said engine and operating in response to operation of said engine to generate an output signal having a frequency proportional to the speed of said engine; a one-shot multivibrator coupled at its input to the output of said sensing means, and operating to produce at its output a pulsed signal of fixed pulse amplitude fixed pulse width and a frequency directly proportional to the frequency of said sensing means output signal; an integrator coupled at its input to the output of said multivibrator and operating to produce at its output a d.c. voltage of a level directly proportional to the frequency of said multivibrator output signal; a second source of reference d.c. voltage of a level directly proportional to a preselected minimum speed of said engine; a voltage comparator having first and second inputs, said first input being coupled to said second source of reference d.c. voltage, said second input being coupled to the output of said integrator, and operating to produce at the output thereof a maximum d.c. voltage level when the voltage level at said second input is relatively higher than the voltage level at said first input and a minimum d.c. voltage level when the voltage level at said second input is relatively lower than the voltage level at said first input; second switching means having normally closed contacts coupled in series between said exhaust blower and said power source for said blower and a control input coupled to the output of said voltage comparator such that said normally closed contacts remain closed in response to a minimum d.c. voltage coupled to said control input and open in response to a maximum d.c. voltage coupled to said control input whereby said exhaust blower is automatically actuated when the speed of said engine falls below said preselected minimum speed; and third switching means having normally open, manually operable contacts coupled in parallel with said first switching means whereby said starter solenoid circuit may be manually completed prior to the expiration of said predetermined period of time.