Water temperature control for diesel engines

Claim 2

Apparatus for controlling temperature of a coolant in a circulating coolant system comprising probe means for sensing the temperature of said coolant at a point in said system, said probe means producing a voltage substantially proportional to said temperature, said voltage being applied to one input of comparison means having a second input to which is applied a reference voltage, said comparison means having a first output level when the voltage of said probe is below said reference voltage and a second output level when the voltage of said probe is above said reference voltage, the output of said comparison means being applied to an input of amplifier means responsive to changes in the output level of said comparison means to actuate regulating means for regulating the temperature of said coolant.

Claim 3

Apparatus as claimed in claim 1 wherein the voltage of said probe is also applied as an input to a plurality of additional comparison means each having a second input to which is applied a different reference voltage, each comparison means having a first output level when the voltage of said probe is below the reference voltage applied to its second input and a second output level when the voltage of said probe is above the reference voltage applied to its second input, the output of each comparison means being applied to an input of a different amplifier means, there being a different amplifier associated with each comparison means, each amplifier means being responsive to changes in the output level of its associated comparison means to actuate regulating means associated therewith for regulating the temperature of said coolant.

Claim 4

Apparatus as claimed in claim 2 wherein the reference voltage for each comparison means is manually adjustable.

Claim 5

Apparatus as claimed in claim 2 wherein each different reference voltage is related to a different temperature of said coolant.

Claim 6

Apparatus as claimed in claim 2 wherein a further comparison means is provided having the voltage of said probe applied to one input and a reference voltage applied to a second input, the reference voltage applied to the second input of said further comparison means being lower than any range of voltages adapted to be produced by said probe when sensing the temperature of said coolant, said further comparison means producing an output unless the output from said probe is interrupted in which case its output ceases and causes actuation of a warning mechanism.

Claim 7

Apparatus as claimed in claim 2 wherein the reference voltage for each comparison means is provided by a set point circuit, there being a different set point circuit associated with each comparison means, each set point circuit having means for introducing a hyteresis function in the voltage applied to the second input of its associated comparison means whereby the output of its associated comparison means changes from said first level to said second level at a value of probe voltage slightly higher than a value of probe voltage which will cause the output of the assOciated comparison means to change from said second level to said first level.

Claim 8

Apparatus as claimed in claim 6 wherein each set point circuit comprises a potentiometer having a substantially constant voltage applied across it, said potentiometer having an adjustable tap connected to the second input of its associated comparison means.

Claim 9

Apparatus as claimed in claim 7 wherein each said set point circuit includes means for increasing the voltage at said adjustable tap when the output of its associated comparison means is at said second level.

Claim 10

Apparatus as claimed in claim 8 wherein said potentiometer has a first end connected to a positive DC voltage source and a second end connected to ground and the means for increasing the voltage at said adjustable tap when the output of its associated comparison means is at said second level comprises a first diode and a second diode, each having an anode and a cathode, said first diode having its anode connected to the anode of said second diode and to the output of the associated comparison means, the cathode of said first diode being connected to the first end of said potentiometer and the cathode of said second terminal connected to said adjustable tap.

Claim 11

Apparatus as claimed in claim 1, wherein said probe comprises a hollow elongated metal tube having a closed end and an open end, said closed end being adapted to be inserted in said coolant, a thermistor being contained in said tube adjacent said closed end and having electrical leads extending from said open end.

Claim 12

Apparatus as claimed in claim 4, wherein said probe comprises a hollow elongated metal tube having a closed end and an open end, said closed end being adapted to be inserted in said coolant, a thermistor being contained in said tube adjacent said closed end and having electrical leads extending from said open end.

Claim 13

Apparatus as claimed in claim 7, wherein said probe comprises a hollow elongated metal tube having a closed end and an open end, said closed end being adapted to be inserted in said coolant, a thermistor being contained in said tube adjacent said closed end and having electrical leads extending from said open end.

Claim 14

Apparatus as claimed in claim 2 wherein the coolant system is adapted to cool an internal combustion engine and said coolant is heated by said engine and cooled by a radiator and said probe is responsive to the temperature of the coolant after passage through said radiator.

Claim 15

Apparatus as claimed in claim 13 comprising a further probe responsive to the temperature of said coolant after heating by said engine, said further probe being connected to means adapted to cause full cooling of said engine upon detection of a temperature above a first predetermined temperature and to means adapted to actuate or alarm upon detection of a temperature above a second predetermined temperature and to means adapted to shut down the engine upon detection of a temperature above a third predetermined temperature.

Claim 16

Apparatus as claimed in claim 14 comprising a third probe adapted to detect loss of coolant from said coolant system below a predetermined minimum, said third probe being connected to means for shutting down said engine upon detection of loss of coolant below said predetermined minimum or upon short circuiting or open circuiting of said third probe.

Claim 17

Apparatus as claimed in claim 15 including means for indicating open circuiting of said further probe.

Claim 18

Apparatus as claimed in claim 15 wherein said third probe is provided with an electrical heater, said heater producing insufficient heat to influence said third probe when it is immersed in coolant but causing said third probe to produce an output when said third probe is not immersed in coolant.

Claim 19

Apparatus as claimed in claim 2, wherein said probe comprises a hollow elongated metal tube having a closed end and an open end, said closed end being adapted to be inserted in said coolant, a thermistor being contained in said tube adjacent said closed enD and having electrical leads extending from said open end.

Claim 20

Apparatus as claimed in claim 3, wherein said probe comprises a hollow elongated metal tube having a closed end and an open end, said closed end being adapted to be inserted in said coolant, a thermistor being contained in said tube adjacent said closed end and having electrical leads extending from said open end.

Claim 21

Apparatus as claimed in claim 5, wherein said probe comprises a hollow elongated metal tube having a closed end and an open end, said closed end being adapted to be inserted in said coolant, a thermistor being contained in said tube adjacent said closed end and having electrical leads extending from said open end.

Claim 22

Apparatus as claimed in claim 6, wherein said probe comprises a hollow elongated metal tube having a closed end and an open end, said closed end being adapted to be inserted in said coolant, a thermistor being contained in said tube adjacent said closed end and having electrical leads extending from said open end.

Claim 23

Apparatus as claimed in claim 8, wherein said probe comprises a hollow elongated metal tube having a closed end and an open end, said closed end being adapted to be inserted in said coolant, a thermistor being contained in said tube adjacent said closed end and having electrical leads extending from said open end.

Claim 24

Apparatus as claimed in claim 9, wherein said probe comprises a hollow elongated metal tube having a closed end and an open end, said closed end being adapted to be inserted in said coolant, a thermistor being contained in said tube adjacent said closed end and having electrical leads extending from said open end.

Claim 25

Apparatus as claimed in claim 16 wherein said third probe is provided with an electrical heater, said heater producing insufficient heat to influence said third probe when it is immersed in coolant but causing said third probe to produce an output when said third probe is not immersed in coolant.