Abstract:
An electronic lock-out tag-out system comprising a transmitter lock and a portable receiver. One or more switches of the transmitter lock is connected to a utility box or the like and are actuated when the transmitter lock is moved or removed. When the switch is activated, an alarm is sounded in the transmitter lock and a signal is transmitted to the receiver to sound an alarm in the receiver.

Description:
RELATED APPLICATION DATA 
   This application is a continuation-in-part of U.S. Pat. No. 7,026,932, issued Apr. 11, 2006, Ser. No. 10/435,997, filed on May 12, 2003. 

   The invention relates to safety devices. More particularly, the invention relates to an electronic apparatus for isolating equipment during maintenance or service work to ensure that personnel are not injured from accidental machine start-ups or electrical shock. 
   BACKGROUND 
   During installation, service and maintenance of powered equipment, service personnel such as electricians must assure that the equipment is isolated from its power source. Examples of such equipment include, but are not limited to, high voltage power supplies, milling machines, boilers, electron microscopes, elevators, fan systems, and lasers. Although the power source is usually electrical, other power sources such as mechanical, hydraulic, pneumatic, chemical, and thermal may be involved. 
   When the power source and the equipment are in the same room, isolation is not difficult. However, more often than not, the power source, e.g. breaker box, is located relatively far away from the equipment. Thus, it is possible that after the equipment is isolated at the power source it may be inadvertently powered on by other personnel who do not know that the equipment was intentionally powered off. Work situations where unexpected energizing or start-up can occur include new construction, installation or set-up of equipment, and the adjustment, inspection, maintenance, repair, and service of machines and equipment. 
   “Lock-out” and “Tag-out” refer to safe methods for the complete power isolation of equipment during maintenance or service work. OSHA regulations 29 CFR 1910.147 and 1926.416 require the use of locks or tags at control points such as breaker boxes as warning devices to ensure that personnel are not injured from accidental machine start-ups. While many lock-out and tag-out solutions perform well, none are fool proof. For example, tag-out solutions assume that all personnel can read the same language. Although lock-out solutions do not require literacy on the part of personnel, lock-outs are difficult to install and often require that the device to be locked is pre-equipped with a lock receiving apparatus. In addition, a lock-out may be bypassed intentionally or accidentally without the knowledge of the affected personnel. 
   SUMMARY OF THE INVENTION 
   One preferred embodiment of the present invention provides an electronic lock-out tag-out safety device which includes two parts: a transmitter lock and a portable receiver. The transmitter lock is designed to be attached to a utility box or power switch and to transmit a signal which is received by the portable receiver which is proximate the affected personnel. The presently preferred transmitter lock includes one or more electromagnets which are activated by a key switch on the transmitter lock. Turning this key switch also arms the transmitter. The transmitter lock also includes a spring biased switch on the same side of the transmitter lock as the magnets. The switch is coupled to an alarm. When the transmitter lock is positioned on a utility box or power switch, the spring biased switch is depressed. If the transmitter lock is removed, a spring biases the switch outwardly and signals an alarm to sound at both the transmitter lock and the receiver. The transmitter lock can also be provided with a vibration sensor which is activated and sounds an alarm whenever the transmitter/lock is moved. Preferably, the alarms will sound both at the transmitter lock and at the receiver until the affected personnel uses a key to turn off the alarm at the transmitter lock. The transmitter lock preferably also includes indicia indicating the name or some other identifying information of the affected personnel. 
   The various embodiments of the present invention advantageously provide a lock-out tag-out system which does not rely on the literacy of personnel, cannot be bypassed without the knowledge of the affected personnel, and is easy to attach to a variety of different power switches. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is perspective view of a transmitter lock and a portable receiver according to one embodiment of the invention with the transmitter lock attached to an electrical cabinet. 
       FIG. 2  is a perspective view of a transmitter lock attached to another type of cabinet. 
       FIG. 3  is a perspective view of a transmitter lock attached to a power switch. 
       FIG. 4  is a perspective view of a transmitter lock of one embodiment of the present invention showing a key switch. 
       FIG. 5  is a perspective view of a transmitter lock of one embodiment the present invention with a spring biased switch and hinged door. 
       FIG. 6  is a partially cut away perspective view of a transmitter lock of one embodiment of the present invention. 
       FIG. 7  is a partially cut away perspective view of a portable receiver of one embodiment of the present invention. 
       FIG. 8  is a schematic diagram of a transmitter lock of one embodiment of the present invention. 
       FIG. 9  is a schematic diagram of a portable receiver of one embodiment of the present invention. 
       FIG. 10  is a partially cut away perspective view of a transmitter showing a key-actuated magnet. 
       FIG. 11  is a partially cut away perspective view of a transmitter with a permanent magnet and an electrical key switch. 
       FIG. 12  is a partially cut away perspective view of a transmitter within an electromagnet. 
   

   DETAILED DESCRIPTION 
     FIG. 1  illustrates one electronic lock-out tag-out system according to one embodiment of the present invention which comprises a transmitter lock  10  and a portable receiver  12 . The transmitter lock  10  includes a speaker  14 , an antenna  16 , editable indicia  17  and an outwardly attending spring biased switch  28  best shown in  FIG. 5 . The indicia  17  preferably indicates the name and location of the affected personnel. The portable receiver  12  includes a speaker  18 , and antenna  20 , and a power switch  22 . 
   As illustrated in  FIG. 1 , the transmitter lock  10  is attached to a utility box  1  straddling the door  2  and the door frame  3 . The attachment is made by one or more magnets (described in detail below) in the transmitter lock  10 . It will be appreciated that when the transmitter lock  10  is mounted as shown in  FIG. 1 , the door  2  of the utility cabinet  1  cannot be opened without moving or removing the transmitter lock  10 . Movement of the transmitter lock enables the spring biased switch to extend and a signal is sent to one, and preferably both, audible alarms. A visible signal can be provided in addition to or in place of the audible signal. Other types of motion switches, such as vibration sensors can also be used without departing from the scope of the present invention. 
     FIG. 2  illustrates an alternative placement of the transmitter lock  10  which utilizes a folding flap  26  (described in detail below) to obstruct the door  5  of utility cabinet  4 . The flap  26  is long enough to extend over the door frame  6  and cover a portion of the door  5 . 
     FIG. 3  illustrates yet another placement of the transmitter lock  10  to cover a power switch  7  thereby preventing the switch from being closed without removing the transmitter lock  10 . 
     FIGS. 4-6  illustrate additional details of the transmitter lock  10 . As shown in  FIGS. 4 and 5 , the exterior of the illustrated transmitter lock  10  comprises a key switch  24  and folding flap  26  which is adjacent to the spring biased switch  28 . As seen best in  FIG. 5 , the flap  26  includes an opening  27  through which the switch button  28  may pass when the flap  26  is folded shut as shown in  FIG. 4 . 
     FIG. 6  illustrates the interior of the transmitter lock  10  which includes a circuit board  30  and a battery  32 . As shown in  FIG. 6 , a permanent magnet  31  is placed on one side of the circuit board  30  and another permanent magnet  33  surrounds the key switch  24  on the other side of the circuit board  30 . The electrical components of the transmitter lock  10  are described in further detail below with reference to  FIG. 8 . 
     FIG. 7  illustrates the interior of the portable receiver  12  which includes a circuit board  34  and a battery  36 . The electrical components of the portable receiver  12  are described in further detail below with reference to  FIG. 9 . 
   Turning now to  FIG. 8 , an exemplary transmitter circuit is illustrated in a schematic diagram. It will be noted that there are no electromagnets in this embodiment and that the key switch is not illustrated. The diagram does show a magnetic reed switch A 2  which deactivates the transmitter when it is disassembled, a vibration contact switch A 3  which activates the transmitter when it is moved, as well as the spring biased switch A 4 . A list of the electrical components is listed below in Table 1. It will be noted that the frequency of the transmitter is controlled by the crystal A 10  which is preferably in the 49-50 MHz range, a band which is available for public use in the U.S. Other types of motion switches, such as vibration sensors can also be used without departing from the scope of the present invention. 
   
     
       
             
           
             
             
             
           
         
             
               TABLE 1 
             
           
           
             
                 
             
             
               TRANSMITTER PARTS 
             
           
        
         
             
                 
               Part Number 
               Description 
             
             
                 
                 
             
             
                 
               A1 
               9 volt battery 
             
             
                 
               A2 
               magnetic reed switch (normally open) 
             
             
                 
               A3 
               vibration contact switch (normally open) 
             
             
                 
               A4 
               spst momentary contact push button switch 
             
             
                 
               A5 
               spst relay 
             
             
                 
               A6 
               antenna 
             
             
                 
               A7 
               choke 
             
             
                 
               A8 
               choke 
             
             
                 
               A9 
               8-ohm 0.5 watt speaker 
             
             
                 
               A10 
               49.860 MHz crystal 
             
             
                 
               A11 
               output transformer 
             
             
                 
               T1 
               NPN K.8E C3192 
             
             
                 
               T2 
               NPN F22L2 9843 
             
             
                 
               T3 
               NPN W81 F824 
             
             
                 
               T4 
               NPN C9014 C-7L 
             
             
                 
               R1 
               47 ohms 
             
             
                 
               R2 
               12K ohms 
             
             
                 
               R3 
               10 ohms 
             
             
                 
               R4 
               320 ohms 
             
             
                 
               R5 
               100K ohms 
             
             
                 
               R6 
               2.7K ohms 
             
             
                 
               R7 
               150K ohms 
             
             
                 
               R8 
               27 ohms 
             
             
                 
               C1 
               33 pF 
             
             
                 
               C2 
               22 pF 
             
             
                 
               C3 
               15 pF 
             
             
                 
               C4 
               403 pF 
             
             
                 
               C5 
               403 pF 
             
             
                 
               C6 
               47 uF 
             
             
                 
               C7 
               203 pF 
             
             
                 
                 
             
           
        
       
     
   
   Turning now to  FIG. 9 , an exemplary receiver circuit is illustrated in a schematic diagram. It will be noted that the receiver is not crystal controlled but is tunable via the choke A 3 . A list of the electrical components of the receiver is listed below in Table 2. 
   
     
       
             
           
             
             
             
           
         
             
               TABLE 2 
             
           
           
             
                 
             
             
               RECEIVER PARTS 
             
           
        
         
             
                 
               Part Number 
               Description 
             
             
                 
                 
             
             
                 
               A1 
               choke 
             
             
                 
               A2 
               antenna 
             
             
                 
               A3 
               choke 
             
             
                 
               A4 
               output transformer 
             
             
                 
               A5 
               8-ohm 0.5 watt speaker 
             
             
                 
               A6 
               9 volt battery 
             
             
                 
               A7 
               spst switch 
             
             
                 
               T1 
               NPN K.8E C3192 
             
             
                 
               T2 
               NPN F22L2 9843 
             
             
                 
               T3 
               NPN W81 F824 
             
             
                 
               T4 
               NPN C9014 C-7L 
             
             
                 
               R1 
               4.7K ohms 
             
             
                 
               R2 
               47 ohms 
             
             
                 
               R3 
               15K ohms 
             
             
                 
               R4 
               8.2K ohms 
             
             
                 
               R5 
               330 ohms 
             
             
                 
               R6 
               1K ohms 
             
             
                 
               R7 
               150K ohms 
             
             
                 
               R8 
               4.7K ohms 
             
             
                 
               R9 
               47 ohms 
             
             
                 
               C1 
               332 pF 
             
             
                 
               C2 
               33 pF 
             
             
                 
               C3 
               22 pF 
             
             
                 
               C4 
               502 pF 
             
             
                 
               C5 
               50 vlu 
             
             
                 
               C6 
               403 pF 
             
             
                 
               C7 
               16 v47 
             
             
                 
               C8 
               203 pF 
             
             
                 
                 
             
           
        
       
     
   
   According to an alternative embodiment of the present invention, as shown in  FIG. 10 , a switch-actuated, most preferably key-actuated, magnet  133  of the type commonly used in a magnetic base is employed to removably connect a transmitter to an electrical device. According to a still further embodiment shown in  FIG. 11 , if a permanent magnet  233  is utilized, it is within the scope of the present invention to add an electrical key switch  105  to arm the alarm.  FIG. 12  illustrates an electromagnet  333  wired in parallel to the circuit. Preferably, actuation of magnet  133 , and actuation of an electromagnet  333 , will also arm the alarm.