Abstract:
A mobile refrigerator unit is operated remotely via wireless technology using a system with a local maintenance switch. A local override switch turns the refrigerator unit on and off, but keeps it on in the event of failure of the maintenance switch.

Description:
RELATED APPLICATIONS 
     This application is a continuation of U.S. application Ser. No. 12/103,629 filed 15 Apr. 2008, which application is incorporated herein as if fully recited herein. This application also claims the benefit of U.S. Provisional Application No. 61/153,287 filed 17 Feb. 2009. 
    
    
     FIELD 
     This invention relates to remote monitoring and control of mobile refrigeration units, and particularly for railroad cars, although the system of the aforementioned patent is applicable to refrigeration trucks and other mobile units. 
     BACKGROUND 
     U.S. Pat. No. 6,863,222, assigned to the same assignee as the present application, discloses a local power switch which, when turned off, completely disables a so-called reefer (mobile refrigeration) unit, and a secondary remote switch to turn the mobile refrigeration unit on and off. U.S. application Ser. No. 12/103,629 filed 15 Apr. 2008 discloses remote control of the power applied to mobile refrigeration units by a wireless telematics system, while still allowing for local control when desired. These arrangements are suitable for many applications but exhibit some shortcomings. 
     An object of this system of invention is to improve the system of the aforementioned patent and applications. 
     SUMMARY OF EMBODIMENTS OF THE INVENTION 
     According to an embodiment of the invention, a remotely controlled maintenance switch allows a local switch to turn the reefer on and off, but the system always maintains power to the reefer even if the local switch was set in an off position. 
     The various features of novelty that characterize the system of the invention are pointed out in the claims forming a part of this specification. Other objects and advantages of the system of the invention will be evident from the following detailed description when read in light of the attached drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a block diagram of a system embracing the structure shown in  FIG. 2  and embodying features of the invention. 
         FIG. 2  is a block diagram of a reefer control arrangement embodying features of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
       FIG. 1  illustrates a system for controlling a so-called reefer unit, i.e. mobile refrigeration unit RE 1  on a railroad refrigeration car RC 1 . According to various embodiments the car RC 1  is a motor truck or other mobile device carrying the refrigeration unit. A control unit in the car monitors and controls the temperature and operation of the refrigeration unit. An antenna AN 1  places the control unit into communication with a remote station RST 1  via a bi-directional link BL 1 . The remote station RST 1  transmits instructions, via the bi-directional link BL 1  and the antenna ANI, to the control unit to establish desired temperature and other conditions in the refrigeration unit RE 1 . 
     According to various embodiments, the bi-directional link BL 1  is a wireless link, and/or a station-to-station link, and/or one communicating with another station and/or via other wireless links or land lines, the Internet, or a combination of these, with the remote station RST 1 . According to yet another embodiment of the system, the bi-directional link BL 1  includes one or more satellites, alone or in combination with other links. In effect the bi-directional link BL 1  represents a communication system generally. According to an embodiment, the rail car RC 1  is one of many, each carrying an antenna for allowing the rail car to communicate with the remote station RST 1  via the bidirectional link BL 1 . The remote station may thus control refrigeration in a fleet of vehicles, rail or truck or even ships. 
     The remote station RST 1  remotely controls the power to the refrigeration unit RE 1  via the bi-directional link BL 1 , the antenna AN 1 , and the control unit CU 1 . 
       FIG. 2  illustrates details of the system of  FIG. 1 . In  FIG. 2 , the antenna AN 1  on the car RC 1  receives and transmits data from and to the remote station RST 1 . In the car RC 1 , a control unit CU 1  receives and transmits data to and from the remote station RST 1  via the bidirectional link BL 1  and the antenna AN 1 , and applies it to a transceiver TR 1  in a refrigeration unit RE 1 . The remote station RST 1  normally controls the temperature and other operating characteristics of the refrigeration unit RE 1 . 
     Maintenance Switch Closed (Normal/Remote Control) 
     When closed, maintenance switch MS 1  causes the control unit CU 1  to issue a signal RM 1  to energize a relay control RL 1  and connect a common contact CC with a contact NO. In this energized condition the relay control RL 1  connects a battery BA  1  with the reefer unit RE 1 , via a contact CT 1  of a local switch LS 1  in a local display panel DP 1 . The battery BA 1  then supplies power to the reefer unit regardless of the position of the local switch LS 1 . The control unit CU 1  receives the status of the maintenance switch via a feedback signal at a maintenance switch monitor input and forwards the feedback signal to the remote station RST 1 . 
     Maintenance Switch Opened (Maintenance Mode/Safety Setting/Local Control) 
     If the maintenance switch MS 1  is open, the signal RM 1  fails to appear at the relay control RL 1 . The latter then assumes its unenergized status and the relay armature connects the common contact CC with the contact NC. This places the switch LS 1  in series between the battery BA 1  and the reefer unit RE 1 . Now, a maintenance person or other local workman can control the power to the reefer unit RE 1  as needed. Typically, a site operator would turn the switch LS 1  OFF prior to unloading the refrigeration car. The site operator would turn it ON prior to loading the car so that it will be cool enough to refrigerate the cargo when it is loaded. 
     Opening of the Maintenance Switch MS 1  prevents relay RL 1  from being energized. This introduces a safe mode for technicians servicing the equipment, in that the system cannot be turned on remotely. It also provides for a way of turning off the system locally should it be powered on remotely. 
     OPERATION 
     In its energized (NO) position, relay control CL 1  applies power directly to the reefer unit RE 1  regardless of the position of switch LS 1 . Assuming that the maintenance switch MS 1  is closed (i.e., normal operation), this allows control unit CU 1  to power the reefer unit RE 1  on and off as desired by means of signal RM 1  even if switch LS 1  is open. Since the control unit CU 1  is part of a wireless system, by extension, the reefer power can be controlled from a remote station RST 1 . 
     Power is applied to the reefer unit through the common contact CC of relay RL 1 . In its de-energized (NC) position, the relay control RL 1  provides a power path to the reefer RE 1  from the existing local switch LS 1  mounted on the display panel of the reefer unit RE 1 . Thus, when switch LS 1  is closed, the reefer unit RE 1  is powered on; when switch LS 1  is opened, the reefer is powered off. 
     With the switch MS 1  closed, the reefer unit RE 1  may be started remotely to be checked-out (“pre tripped”) and pre-cooled, prior to loading. This is vital in grocery and dairy distribution centers, where produce is loaded centrally and distributed to stores, where remotely turning off the units is less important (it can be done locally). So the system is a significant improvement in that operationally it serves an important feature set without any consequences of failure and at much lower cost. There is never a need to turn off the unit remotely for customers who operate this way. 
     The present system always maintains power to the reefer RE 1  if it was turned on locally by closing the switch LS 1 . If the relay control RL 1  fails by staying in its normally open position NO, power is applied to the reefer RE 1  from the +12 v supply of battery BA 1  via the contact CT 1 . If the relay control CL 1  fails in its normally closed position NC, current flows to the reefer RE 1  through the local power switch L 51 . Thus, when the operator has closed the local switch LS 1 , the reefer RE 1  will continue to operate even if a failure causes the system to lose control of the relay. 
     In its de-energized NC position, the relay RL 1  provides a power path to the reefer unit RE 1  from a local switch LS 1 , mounted on the display panel DP 1  of the reefer unit RE 1 . Thus, when switch LS 1  is closed, the reefer unit RE 1  is powered on; when LS 1  is opened, the reefer unit RE 1  is powered off. 
     In its energized (NO) position, relay RL 1  applies power directly to the reefer unit RE 1  regardless of the position of switch LS 1 . When a maintenance switch MS 1  is closed, this allows Control Unit CU 1  to power the reefer unit RE 1  on and off as desired by means of signal RM 1  even if LS 1  is open. The control unit CU 1  is part of a wireless system and connected to the antenna AN 1 , the reefer unit power can be controlled from a remote location communicating with the antenna AN 1 . 
     Opening of the maintenance switch MS 1  prevents relay RL 1  from being energized and places the relay RL 1  in the NC position. This introduces a safe mode for technicians to service the equipment, because the system cannot be turned on remotely. It also provides for a way of turning off the system locally should it be powered on remotely. 
     The status of MS 1  is fed back to the control unit CU 1  for reporting back to a remote operator that the switch MS 1  has been activated. 
     The transceiver TR 1  forms part of the reefer unit RE 1  and senses the conditions of operation in the operation unit OP 1  within the reefer unit. A microcontroller MC 1  in the reefer unit RE 1  senses conditions, such as temperature, in the operation unit OP 1  and other parts of the reefer unit. The transceiver TR 1  transmits the conditions sensed to the controller CONT 1  in the control unit CU 1 . The controller CONT 1  then transmits these sensed conditions to the remote station RST 1  via a transceiver and the antenna AN 1 . 
     The system according to an embodiment of the present invention always maintains power to the reefer if it was turned on locally. If the relay RL 1  fails in its normally open position NO, power will be applied to the reefer from the +12 v supply; if the relay fails in its normally closed position NC, power will be applied to the reefer unit RU 1  through the reefer&#39;s local power switch LS 1 . Thus, when the operator has turned ON the reefer locally, the reefer will continue to operate even if a failure causes the system to lose control of the relay RL 1 . 
     Thus the control unit CUI allows a local maintenance person or site operator at the car RC 1  to turn the reefer (refrigeration) unit RE 1  on or off. When the remote station RST 1  turns the refrigeration unit RE 1  off, the local power switch LS 1  allows the local maintenance person to take ultimate authority to turn the refrigeration unit RE 1  on and off. The local power switch LS 1  then, when turned off, completely disables mobile refrigeration unit RE 1 , and when turned, on permits operation of the unit. 
     The system overcomes the effect of a workman inadvertently leaving the local switch LS 1  of the reefer unit RE 1  in its OFF position, which would otherwise would leave the reefer unit without power and render the reefer unit RE 1  inoperative. It surmounts the effect of requiring an operator to be dispatched to the car to return the switch LS 1  to its off position. The control unit CUI provides an alternative path for power to the reefer unit RE 1 , through the normally open contact NO of the relay RL 1 . The switch/relay RL 1  is controlled from the remote station RST 1  with the remote bi-directional link BL 1  and antenna ANI, and can provide power to the reefer unit RE 1  regardless of the state of the local switch LS 1 . 
     The difference between the aforementioned patent and embodiments of the invention reside in part in the following. 
     Both systems offer the ability to remotely turn on the reefer RE 1  with the local switch LS 1  off. An embodiment of the present invention introduces the arrangement in which a maintenance switch MS 1  can prevent the refrigeration from being turned off remotely like the aforementioned patent. This has the advantage of increased reliability, as any failure to any components of the system result in no interruption to the power of the reefer system. In the aforementioned patent a component failure may cause the reefer to lose power. 
     In grocery and dairy distribution centers, where produce is loaded centrally and distributed to stores, remotely turning off the units is less important (it can be done locally). So the system is set without any consequences of failure. Customers who operate this way cannot turn off remotely if the maintenance switch MS 1  is on. 
     While embodiments of the system of the aforementioned patent have been described in detail, it will be evident to those skilled in the art that the system of the aforementioned patent may be embodied otherwise.