Methods and apparatus for monitoring the operation of a transport refrigeration system
First Claim
1. A method of monitoring a transport refrigeration unit which conditions a load in a cargo space to a selected set point temperature via commanded cooling and heating cycles, comprising the steps of:
- determining the temperature of the conditioned load,providing a digital signal as a function of the load temperature and the set point temperature, with each toggle of the least significant bit (LSB) of the digital signal indicating a predetermined change in load temperature,starting timing means having a predetermined timing period in response to the toggling of the LSB,selecting the predetermined timing period as a function of the selected set point temperature,and providing an alarm signal when the selected timing period expires before the next toggle of the LSB.
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Accused Products
Abstract
A transport refrigeration unit, and methods and apparatus for monitoring the operation thereof, with the unit conditioning a load to a selected set point temperature via commanded cooling and heating cycles. A thermostat provides a digital signal as a function of the load temperature and the selected set point temperature, with each toggling of the least significant bit (LSB) thereof indicating a predetermined change in load temperature. A timer initiates a predetermined timing period with each toggling of the LSB, with the timing period being a dynamic function of the selected set point temperature. Expiration of the timing period before the next bit toggle initiates an alarm signal indicating the rate-of-change of load temperature is not within an acceptable limit for the selected set point temperature. A comparison of successive digital signals also results in an alarm signal when the direction of temperature change is not consistent with the commanded operating cycle.
181 Citations
22 Claims
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1. A method of monitoring a transport refrigeration unit which conditions a load in a cargo space to a selected set point temperature via commanded cooling and heating cycles, comprising the steps of:
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determining the temperature of the conditioned load, providing a digital signal as a function of the load temperature and the set point temperature, with each toggle of the least significant bit (LSB) of the digital signal indicating a predetermined change in load temperature, starting timing means having a predetermined timing period in response to the toggling of the LSB, selecting the predetermined timing period as a function of the selected set point temperature, and providing an alarm signal when the selected timing period expires before the next toggle of the LSB. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11)
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12. A transport refrigeration system which conditions a load in a cargo space to a selected set point temperature via cooling and heating cycles, comprising:
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sensor means providing a signal indicative of the temperature of the conditioned load, set point selector means providing a signal indicative of the selected set point temperature, thermostat means which provides a digital signal as a function of the load temperature and the set point temperature, with each toggle of the least significant bit (LSB) of the digital signal indicating a predetermined change in load temperature, timing means, means responsive to the toggling of the LSB for causing said timing means to initiate a predetermined timing period, means dynamically selecting the predetermined timing period of the timing means as a function of the magnitude of the set point temperature, and alarm means responsive to the toggling of the LSB and the predetermined timing period, providing an alarm signal when the selected timing period expires before the next toggle of the LSB. - View Dependent Claims (13, 14, 15, 16, 17, 18, 19, 20, 21, 22)
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Specification