Abstract:
A security gate operating system, is disclosed which comprises an electrically powered motor; a thermally controlled circuit breaker set to remove power to the motor when the motor reaches a preselected threshold temperature; a cooling fan associated with the motor and selectively powered to provide auxiliary cooling to the motor to prevent the motor from overheating; and a cooling fan motor controller, adapted to selectively supply power to the cooling fan when the motor is approaching the threshold temperature. The apparatus can further comprise the cooling fan controller being a thermo-static switch set to close at a preselected temperature below the threshold temperature, or a programmed microprocessor/microcontroller programmed to provide power to the cooling fan at a preselected temperature below the threshold temperature or when the temperature of the motor is about to reach the preselected temperature.

Description:
FIELD OF THE INVENTION 
   The present invention relates to the field of security gate operating systems, and more specifically a method and apparatus for preventing overheating of a security gate operating motor. 
   BACKGROUND OF THE INVENTION 
   It is well known to operate security gates with a motor driven mechanism, and  FIG. 1  shows one form of such a security gate system and  FIG. 2  shows another form of such a security gate.  FIG. 3  shows in more detail the front installation of a drive chain mechanism associated with the form of security gate operating mechanism shown in FIG.  1  and  FIG. 4  shows another form of security gate chain drive operating mechanism, a so-called rear installation, associated with FIG.  2 . It is known to attempt to prevent motor overheating by sensing the overheating or an over-current situation, which can lead to or has led to overheating, and tripping a switch or a circuit breaker, as the case may be, which shuts off the motor. The motor could be shut off in the middle of moving the security gate from a closed position to an open position or from the open position to a closed position. In either event, the gate could be left in a position where it is blocking the passage into or out of the facility for which it is serving as a security gate. Similarly the gate could be left in the fully closed position or essentially the fully closed position, also blocking ingress or egress, or in the fully open or essentially fully open position, thereby no longer serving to operate as a security gate, i.e., preventing unauthorized ingress into the facility. In known systems, this situation is maintained until someone physically resets the circuit breaker of un-trips the switch so as to turn on the motor again, after the overheating/over-current event is ended. Systems of the type existing in the prior art may be required to have thermal shut off breakers, e.g., for Underwriter&#39;s Laboratories certification. such breakers do not allow for resetting except by human intervention, which could result in a security gate being stuck in a certain position until such time as such a breaker is reset. There is a need, therefore, to be able to avoid over-current/overheating circumstances and to automatically recover to the normal mode of operating the security gate motor when the over-current/overheating event has ended. 
   SUMMARY OF THE INVENTION 
   A security gate operating system, is disclosed which comprises an electrically powered motor; a thermally controlled circuit breaker set to remove power to the motor when the motor reaches a preselected threshold temperature; a cooling fan associated with the motor and selectively powered to provide auxiliary cooling to the motor to prevent the motor from overheating; and a cooling fan motor controller, adapted to selectively supply power to the cooling fan when the motor is approaching the threshold temperature. The apparatus can further comprise the cooling fan controller being a thermo-static switch set to close at a preselected temperature below the threshold temperature, or a programmed microprocessor/microcontroller programmed to provide power to the cooling fan at a preselected temperature below the threshold temperature or when the temperature of the motor is about to reach the preselected temperature. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  (Prior Art) shows a security gate operating system of a type in which the present invention may be utilized; 
       FIG. 2  (Prior Art) shows another form of a security gate system of a type in which the present invention may be utilized; 
       FIG. 3  (Prior Art) shows a security gate drive mechanism of the type useful in the security gate operating mechanism of  FIG. 1 ; 
       FIG. 4  (Prior Art) shows another view of the a security gate drive mechanism of the type useful in the security gate operating mechanism of  FIG. 1 , with the security gate in a position opposite from that shown in  FIG. 3 ; 
       FIG. 5  (Prior Art) shows a security gate drive mechanism of the type useful in the security gate operating mechanism of  FIG. 2 ; 
       FIG. 6  (Prior Art) shows an exploded view of the security gate drive mechanism shown in  FIGS. 1 ,  3  and  4 ; 
       FIG. 7  (Prior Art) shows an enlarged view of a portion of the security gate drive mechanism shown in  FIGS. 1 ,  3  and  4 ; 
       FIG. 8  shows a schematic view of a cooling fan control system according to the present invention. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   Turning now to  FIG. 1  (Prior Art), there is shown a known form of security gate system  10 . The security gate system  10  shown in  FIG. 1  is an example of a so-called front installation security gate system  10 . The security gate system  10  has a sliding gate  12 , which is partially mounted for sliding movement by mounting brackets  14  and  16  to wall sections  18  and  20 , respectively. The sliding gate  12  has a pair of rollers  22  that engage a track  24 . The gate is driven by a security gate drive mechanism  26 , as more fully described in regard to  FIG. 3  below. The security gate  12  is driven by a chain drive, more fully described in regard to  FIG. 3  between a pair of physical travel stops  28 . 
   Turning now to  FIG. 2  (Prior Art) there is shown another form of security gate system  10 ′. The security gate system  10 ′ shown in  FIG. 2  is an example of a so-called rear installation security gate system  10 ′. The security gate system  10 ′ also has a sliding gate  12 , which is partially mounted for sliding movement by mounting brackets  14  and  16  to wall sections  18  and  20 , respectively. The sliding gate  12  has a pair of rollers  22  that engage a track  24 . The gate is driven by a security gate drive mechanism  26 , as more fully described in regard to  FIG. 3  below. The security gate  12  is driven by a chain drive, more fully described in regard to  FIG. 3  between a pair of physical travel stops  28 . 
   The difference between the security gate system  10  of FIG.  1  and the security gate system  10 ′ of  FIG. 2  is that the chain drive for operating the security gate  12  through movement of chain  30  runs along the bottom of the gate  12  in the embodiment of FIG.  1  and is fully behind the respective wall section  20  in the embodiment of  FIG. 2 , for added security purposes. The chain  30  is also attached to the security gate  12  and security gate drive mechanism slightly differently as explained in more detail in regard to  FIGS. 3 and 4 . 
   Turning now to  FIG. 3  (Prior Art) there is shown in more detail a security gate drive mechanism  26  for the embodiment of  FIG. 1  as it would appear from a view facing away from the wall section  20  shown in FIG.  1 . The security gate drive mechanism has a chain drive sprocket  40 , which engages the drive chain  30  after it passes around a first pulley  42 . The chain subsequently passes around a second pulley  44 , as shown in FIG.  3 . As also shown in  FIG. 3  the chain  30  is attached to the sliding gate  12  by an attachment mechanism  32 . The attachment mechanism  32  includes an attachment bar  34 , which is attached to the sliding gate  12  as shown in  FIG. 3 , e.g., by welding the attachment bar  34  to the sliding gate  12  in the position shown in FIG.  3 . The attachment mechanism  32  is described in more detail below in regard to FIG.  7 . 
   Turning now to  FIG. 4  (Prior Art) there is shown a view of the sliding gate  12  when it is at the opposite end of its travel. The sliding gate  12  is shown in  FIG. 4  to be attached to the drive chain  30  by a gate extension arm  50 , to which is attached a mounting bar  52 , e.g., by welding to the gate extension arm  50 . The gate extension arm  50  is itself attached to the sliding gate  12 , e.g., by welding the extension arm  50  to the sliding gate  12  in the position as shown in FIG.  4 . The drive chain  30  is in turn connected to the mounting bar  52  by a chain attachment mechanism  54 , which is held on the mounting bar  52  by a nut  56 . The extension arm  50  is cut to a particular size or welded along the lower horizontal portion  12 ″ of the frame of the sliding gate  12  such that the chain is relatively taught when the sliding gate  12  is at the extent of its travel, as shown in  FIG. 4 , and thereafter the chain attachment mechanism  32  and  54  can be threaded through the respective attachment bar  34  and/or  52  to fully tighten the chain before engaging the chain to the respective chain attachment mechanism  32  and/or  54 . 
   Turning now to  FIG. 5  (Prior Art) there is shown a security gate drive mechanism  26  of the type shown in the embodiment of FIG.  2 . Here the drive chain  30  passes over the drive sprocket  40  and around only the first pulley  42 . One end of the drive chain is attached to the sliding gate by an attachment bar  52 , which is attached to the sliding gate  12 , as by welding the attachment bar  56  to the sliding gate  12 , through an attachment mechanism  54  having a nut  56 . The other end of the chain  30  passes around a sprocket  68  rotatably mounted on a sprocket block  66 , which is in turn mounted to a sprocket block post  58 , e.g., by welding the sprocket block  66  to the sprocket block post  58 . The sprocket block post  58  is in turn mounted to the lower horizontal frame member  12 ″ of the sliding gate  12 , as by welding the sprocket block post  58  to the lower horizontal frame member  12 ″ at such a location that the chain is taught in its extension over the sprocket to the mounting bar  34 , to which it is attached by chain attachment mechanism  32 . 
   Turning now to  FIG. 6  (Prior Art), there is shown an exploded view of a security gate drive mechanism  26 , as shown in  FIG. 1  or FIG.  2 . The security gate drive mechanism  26  has a frame  72 . As shown in  FIG. 6 , the pulley wheels  42 ,  44 , which can be, e.g., slotted UHMW rollers adapted to prevent chain slippage off of the drive sprocket  40 , by keeping the drive chain  30  on the pulley wheels  42 ,  44  in their respective slots in alignment with the drive sprocket  40  during operation. The drive chain  30  can be, e.g., a #41 chain. As shown, the pulley wheels  42 ,  44  are attached to the frame  72  by a respective stationary axels  70 , each having a threaded end attached to a respective nut  71 , which may be attached to the frame  72 , as by welding to the frame  72 . The respective pulley wheels  42 , 44  are held in place on the respective axles  70  by a washer  74  and a capped nut  76 . 
   The security gate drive mechanism also includes a motor  80 , which can be, e.g., a one-half horse power instant reversing 120 VAC, 4 amp, 1625 rpm, parking gate motor, such as that made and sold by Leeson, Model No. 100741.50, which can include high speed ball gearings for smoother and quieter operation. In the alternative, the motor  80  can be a permanent magnet 12V DC motor, e.g. that made and sold by TRU-TORQ, Model No. 970-535. The motor  80  has a drive shaft, not shown, that connects to a sprocket wheel  84 , which is part of a sprocket transfer unit  82 . the sprocket transfer unit  82  also has a second sprocket wheel  86 , and a chain or a drive belt  87 , which extends around the sprocket wheels  84  and  86 . A chain shield  88  covers the sprocket wheels  84  and  86  and the chain  87 . The sprocket wheel  86  is attached to an input shaft  92  of a reduction gear  90 , which also has an output shaft  94 . The reduction gear can be, e.g., a 30-1 worm gear reducer with the gears operating in an oil bath, such as that made and sold by Hampton, Model No. M008. Attached to the output shaft  94  of the reduction gear  90  is the chain drive sprocket  40  and a smaller sprocket  96 , internally mounted on the output shaft  94  in relation to the chain drive sprocket  40 . 
   The inner sprocket  96  is connected by a drive chain  98  to a sprocket wheel  100 , which is attached to the end of a limit control spindle  102 , having threads  110 . Moveably mounted on the threads  110  of the motion limit controller spindle  102  are a pair of traveling nuts  112  and  114 . The limit controller spindle  102  is rotatably mounted in a motion limit controller housing  116 , which is in turn attached to the frame  72 . Slideably mounted on the spindle  102  are a pair of adjustably positionable stop members  118  and  120 , which are electrically connected to a controller on a circuit board  132  and can provide a signal indicating that the drive chain  30  has reached one end or the other of its extent of desired motion, as by contact of one or the other of the traveling nuts  112  or  114  with its respective stop member  118  or  120 . 
   Also shown in  FIG. 6  is a controller circuit board housing  130 , which is attached to the frame  72  and in which is contained the controller circuit board  132 . A cover  134  is attached to the housing  130  and spacers  142 , seat the controller circuit board  132  against input/output electrical signal connections  146  by virtue of being screwed into mounting screws  144 , connected to the interior wall of the housing  130 . 
   Turning now to  FIG. 7  (Prior Art), there is shown in more detail the connection of the drive chain to the sliding gate, such as in the embodiments of  FIGS. 1 and 3 . The chain attachment mechanism  32  has a threaded shaft portion  64 , which is threaded into nut  62  after passing through a hole in the attachment bar  34 . The chain attachment mechanism  32  has a flattened attachment extension  60 , to which the chain  30  is attached by passing the pin of the last link of the chain through an opening in the extension  60 . 
   It is also well known in the prior art that the motor  80  of a security gate operating system  10  can come with an internal fan and/or an external fan can in addition be supplied, each of which are in operation whenever the motor  80  is in operation. 
   Turning now to  FIG. 8  there is shown an example of an overheating/overload control circuit  200  according to an embodiment of the present invention. The circuit  200  can include a power source  202  such as a positive 12 volt DC source, which can be supplied through an on/off switch  204  to a motor  206 . The motor can be as described above with respect to the prior art security gate operating mechanism, and can have associated with it a fan  208 . The fan  208  can be internal to the motor  206  housing or external thereto or can be a combination of both such fans, which fan(s)  208  is energized when the motor is energized and in operation. the circuit  200  can also include a ground connection  210 . The circuit  200  can further include an auxiliary fan  220 , which can be energized through a switch, e.g., a thermo-static switch  222 . The thermostatic switch  222  can be a Burnital thermostatic switch. The thermostatic switch  222  can be connected to the casing of the motor, or otherwise in contact with the motor or in sufficiently close proximity to the motor to sense the temperature of the motor, and specifically when the motor has exceeded some threshold temperature and/or is about to exceed some threshold temperature, in order for the auxiliary fan to be turned on in sufficient time to pass air across the outer casing of the motor  206  and/or the motor  206  vent openings, in order to cool the motor  206  sufficiently to prevent operation of the thermal breaker(s), which would result in shutting off the motor and stopping the movement of the security gate until such breaker(s) was reset. eliminated from the prior art is the need to use an oversized motor, or two motor, one as a backup, or an oversized fan always operating when the security gate operating system motor(s) was in operation, causing undue expense, power consumption and increased space requirements. 
   The circuit  200  of the present invention can supply input to the security gate controller contained on the circuit board  132  to provide input to a programmed processor/controller to, e.g., interpolate changes in the temperature of the motor  206 , e.g., from background ambient, or with respect to a selected threshold temperature and/or a series of such threshold temperatures, as may be necessary to determine the point at which to turn on the auxiliary motor  220 . In this event, the thermostatic switch  222  may be replaced with a switch operated by the security gate operating system controller on the circuit board  132 . An algorithm for determining the point at which to turn on the auxiliary fan  220 , can include the following: T AMB +(ΔTEMP/ΔTIME)=THRESHOLD?ON:OFF. 
   While the preferred embodiments of the present invention have been shown and described, it will be apparent to those skilled in the art that various modifications may be made in these embodiments without departing from the spirit of the present invention. For that reason, the scope of the invention is set forth in the following claims: