Abstract:
A motorized safety system which protects the open side of a mezzanine, loading dock or other elevated work area when in use. The safety system is easy to use while requiring only minimal floor space. The safety system comprises two posts, each post having a motor mounted on the top of the post, a control unit for controlling and sychronizing motor operation mounted on the side of one post, a movable arm having a safety net and associated hardware such that when the safety system is in a first position the opening of the mezzanine or loading dock is substantially covered by the net. When the safety system is in a second position, the arm and net are out of the way, allowing access by workers and machinery to and from the open side. The operation of the safety system from the first position to the second position or vice versa is performed remotely using a wireless hand held device that transmits instructions to the control unit, thus further reducing the risk of falling.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation in part under 37 C.F.R. § 153(b) of patent application Ser. No. 08/977,069, filed Nov. 24, 1997, U.S. Pat. No. 6,098,750, issued Aug. 8, 2000, which claims priority under 35 U.S.C. § 119(e) to provisional patent application serial No. 60/031,710, filed Nov. 25, 1996. 
    
    
     STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
     Not Applicable 
     BACKGROUND OF THE INVENTION 
     A warehouse or similar style building typically includes an open-sided mezzanine level which is used for storing pallets of material, as well as a loading dock which is open to the outside at a predetermined height so that trucks, once backed up to the dock, can be easily unloaded. The open sides of the mezzanine and the loading dock pose serious safety risks. A misplaced step by a worker can send the worker over the edge of the mezzanine or loading dock, posing danger to the worker as well as any workers below. A misplaced carton or pallet can also tumble off the mezzanine or loading dock and possibly injure people or materials located below. Injuries resulting from workers or material falling off of open mezzanines and loading docks are one of OSHA&#39;s top ten most frequently violated standards. 
     Previous attempts to reduce the risk of open-sided mezzanines and loading docks have proven relatively unsuccessful. Yellow warning lines painted on the floor have achieved limited results at best. Steel fencing systems have proven effective when closed, but require a great deal of floor space since they typically are swung into and out of position. Further, operating a steel fence system places a worker at the edge of the mezzanine or loading dock, creating a safety hazard of its own. The opening and closing of steel systems require substantial time by one or more employees and as such are costly to use as well as to purchase. Workers tend to avoid using safety systems which interrupt work flow, and when a safety system is not used, it can not afford protection. 
     BRIEF SUMMARY OF THE INVENTION 
     A motorized safety system is disclosed which protects the open side of a mezzanine, loading dock or other elevated work area when in use. The safety system is easy to use while requiring only minimal floor space. The safety system comprises two posts, each post having a motor mounted on the top of the post, a control unit for controlling and sychronizing motor operation mounted on the side of one post, a movable arm having a safety net and associated hardware such that when the safety system is in a first position the opening of the mezzanine or loading dock is substantially covered by the net. When the safety system is in a second position, the arm and net are out of the way, allowing access by workers and machinery to and from the open side. The operation of the safety system from the first position to the second position or vice versa is performed using a wireless hand held device that transmits instructions to the control unit, thus further reducing the risk of falling. 
    
    
     BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING 
     The invention will be more fully understood from the following detailed description taken in conjunction with the accompanying drawings in which: 
     FIG. 1 is a front view of a first embodiment of the safety system in the closed position; 
     FIG. 2 is a front view of the safety system of FIG. 1 shown in the open position; 
     FIG. 3 is a front view of an embodiment of a safety system including multiple posts; 
     FIG. 4 is a front view of a second embodiment of the safety system in the closed position; 
     FIG. 5 is a front view of the safety system of FIG. 4 in a partially open position; 
     FIG. 6 is a front view of the safety system of FIG. 4 in the open position; 
     FIG. 7 is a front view of a further embodiment of the safety system of FIG. 4; 
     FIG. 8 is a front view of a first embodiment of the motorized safety system in the closed position. 
     FIG. 9A is a perspective wireframe view of the motor and drive assembly of a vertical post of the motorized safety system of FIG. 8; 
     FIG. 9B is a front wireframe view of the motor and drive assembly of a vertical post of the motorized safety system of FIG. 8; 
     FIG. 9C is a top wireframe view of the motor and drive assembly of a vertical post of the motorized safety system of FIG. 8; 
     FIG. 9D is an illustration of a modified extrusion of the motorized safety system of FIG. 8; 
     FIG. 10 is a block diagram of the electronic circuitry of the motorized safety system. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring to FIG. 1, a first embodiment of a safety system  10  for use with a mezzanine opening or other elevated work area is shown. In warehouses, mezzanine shelving is typically used to hold inventory. The inventory is typically placed on the shelving with a fork lift. Often, employees must also work on these upper levels to maneuver the inventory. A fall hazard arises when employees work in the area between the inventory and the edge of the shelving. Employers are required to protect their employees from such a fall hazard. However, it is difficult to put up a barrier to keep people from falling because it interferes with the operation of the fork lift. 
     The system  10  in this embodiment comprises two generally vertical posts  20  and  30 , a generally horizontal top arm  40 , a bottom assembly  50 , a safety net  60 , a cable system and associated hardware. The posts  20  and  30  are permanently secured to a structure  15  such as the mezzanine floor and may include a guide rod  25  and  35  for moveable securement of the safety net  60 . The safety net  60  is suspended between the posts  20  and  30 , the top arm  40  and the bottom assembly  50  by spring snap links  95  or the like. A first rope or cable  70  is strung from the ground level, over first pulley  92  disposed at the bottom of post  20 , through the post  20 , over a second pulley  91  disposed at the top of the post and attached to one end of the top arm  40 . A second rope or cable  80  is strung from the ground level, over third pulley  93  disposed at the bottom of post  30 , through the post  30 , over a fourth pulley  94  disposed at the top of the post  30  and attached to a second end of the top arm  40 . Additional pulleys may also be utilized to further guide the cables. 
     The bottom assembly is secured between the bottom of the posts  20  and  30 . The bottom assembly can be an arm, a plurality of anchors fixed to the structure, or a cable extending between the posts  20  and  30 . 
     The first cable  70  and second cable  80  allow for movement of the top arm from a first position wherein the top arm is disposed between the top of the posts, and a second position wherein the top arm is disposed between the bottom of the posts  20  and  30 . 
     When the top arm is disposed at it&#39;s first position, the safety net  60  substantially covers an opening defined by the posts  20  and  30 , the bottom assembly  50 , and the top arm  40 . In such a position the risk that a worker or material will fall off the mezzanine shelf is greatly reduced. 
     When the cables  70  and  80  are extended, the weight of the top arm  40  causes the system to retract, with the top arm and safety net falling below the top surface of the mezzanine shelf as shown in FIG.  2 . In this second position the safety net  60  is out of the way, and allows access between the posts  20  and  30  by people or machinery. The cables  70  and  80  allow for the movement of the top arm from the first position to the second position. The cables are secured such as by being tied to “c cleats”, fixed in position by operation of cable locks, or by some other securing device. A motor  85  may be used to provide for extension and retraction of the cables. The cables allow for operation of the safety system between its first and second positions remotely from the opening, thereby removing a safety risk to the operator. 
     Referring now to FIG. 3, a series of safety systems  10  are shown installed along an upper level. While only two systems are shown, it should be realized that any number of systems could be connected together using a plurality of safety nets, center posts, a left post, a right post and associated hardware. 
     The system in this embodiment comprises two generally vertical posts  20  and  30 , a center post  25 , a pair of generally horizontal top arms  40  and  40 ′, a pair of bottom assemblies  50  and  50 ′, a pair of safety nets  60  and  60 ′, and associated hardware. The posts  20  and  30  are permanently secured to a structure  15  such as the mezzanine floor as is center post  25 . Safety net  60  is suspended between the posts  20  and  25 , the top arm  40  and the bottom assembly  50  by spring snap links  95  or the like. Safety net  60 ′ is suspended between the posts  30  and  25 , the top arm  40 ′ and the bottom assembly  50 ′ by spring snap links  95  or the like. 
     A first rope or cable  70  is strung from the ground level, over first pulley  92 , through the post  20 , over a second pulley  91  disposed at the top of the post  20  and attached to a first end of the top arm  40 . A second rope or cable  80  is strung from the ground level, over a third pulley  97  disposed at the bottom of the center post  25 , through the center post  25 , over a fourth pulley  96  disposed at the top of the post  25  and attached to a second end of the top arm  40 . A third cable  101  is strung from the ground level, over a fifth pulley disposed at the bottom of the center post  25 , through the center post  25 , over a sixth pulley  99  disposed at the top of the center post  25  and attached to a first end of the top arm  40 ′. A fourth cable  102  is strung from the ground level, over seventh pulley  93  disposed at the bottom of post  30 , through the post  30 , over an eighth pulley  94  disposed at the top of the post  30  and attached to a second end of the top arm  40 ′. 
     The bottom assembly  50  is disposed between the bottom of the posts  20  and  25 . The bottom assembly  50 ′ is disposed between the bottom of posts  25  and  30 . The bottom assemblies can be an arm, a plurality of anchors fixed to the structure, or a cable extending between the posts  20  and  25 , and between the posts  25  and  30 . 
     The first cable  70  and second cable  80  allow for movement of the top arm  40  from a first position wherein the top arm is disposed between the top of the posts  20  and  25 , and a second position wherein the top arm  40  is disposed between the bottom of the posts  20  and  25 . The third cable  101  and fourth cable  102  allow for movement of the top arm  40 ′ from a first position wherein the top arm  40 ′ is disposed between the top of the posts  25  and  30 , and a second position wherein the top arm  40 ′ is disposed between the bottom of the posts  25  and  30 . 
     When the top arms are disposed at their first position, the safety net  60  substantially covers an opening defined by the posts  20  and  25 , the bottom assembly  50 , and the top arm  40 . Also in such a position the safety net  60 ′ substantially covers an opening defined by the posts  25  and  30 , the bottom assembly  50 ′ and the top arm  40 ′. In such a position the risk that a worker or material will fall off the mezzanine shelf is greatly reduced. 
     When the cables  70  and  80  are extended, the weight of the top arm  40  causes the system to retract, with the top arm  40  and safety net  60  falling below the top surface of the mezzanine shelf. In this second position the safety net  60  is out of the way, and allows access between the posts  20 ,  30  by people or machinery. Similarly, when the cables  101  and  102  are extended, the weight of the top arm  40 ′ causes the system to retract, with the top arm  40 ′ and safety net  60 ′ falling below the top surface of the mezzanine shelf. In this second position the safety net  60 ′ is out of the way, and allows access between the posts  20  and  25  or  25  and  30  by people or machinery. The operation of moving the system between the first and second positions can occur independently. For example, thus safety net  60  could be in the first position while safety net  60 ′ is in the second position. 
     Referring now to FIGS. 4-7 a further embodiment  100 , in this instance for a loading dock or other elevated work area, is shown. The loading dock safety system  100  is used to keep people from falling off of elevated loading docks when the bay door is open and there is no truck covering the opening. The system  100  is readily employed and deployed, multiple times per day. The system  100  is out of the way of the business activities at the facility when not in use. 
     In this embodiment the safety system  100  comprises a lower arm or post  120  secured to a floor or other structure just inside one side of the elevated loading dock door. Attached to this lower post  120  is a hinged upper arm or post  140 . The upper arm  140  may be telescopic such that a first section  140 ′ of the upper arm is receivable within a second section  140 ″ of the upper arm. The safety net  160  is secured to the upper arm with circular links. The upper arm is movable between a first position and a second position. 
     In the first position, the upper arm  140  is generally horizontal and is extended across the entire opening of the bay door (not shown) and attached to another post or reception arm  130  permanently mounted to the floor just inside the other side of the elevated loading dock door. A portion of the safety net  160  is permanently attached at the top to the outer most point of the arm so that the net  160  slides open and closed with the arm and does not bunch up when the arm is raised. Furthermore, the bottom corner, closest to the hinged post is permanently affixed to the hinged post by link  180 . The opposite bottom corner is removably attached to the receiving post, via a spring snap link  190 , each time the arm is engaged and disengaged. In the first position the safety net substantially covers the loading dock opening, and greatly reduces the risk of a worker or material falling off the loading dock. 
     In the second position, the arm is raised upright so as to be out of the way of the door (similar to a rail road crossing gate). The upper arm  140  can be locked in this position by lock  170 . When the safety system  100  is to be engaged, the arm is unlocked from its first upright position and lowered to its second generally horizontal position. A pressurized shock  150  may be included to assist in the lifting and lowering of the upper arm. 
     Referring now to FIG. 7, the safety system is shown including a guide rod  199 . Guide rod  199  is pivotally mounted to upper arm  140 , and keeps the safety net  160  extended across the opening when the upper arm  140  is extended. The guide rod  199  is received by receptacle  198  and is maintained therein, thus removing the need to manually connect the corner of the net to the receiving arm  130 . 
     A motorized safety system  200  for protecting an open side of a work area positioned on an elevated structure  215  is illustrated in FIG.  8 . First and second motors  222 ,  232  are mounted on first and second vertical posts  220 ,  230 , respectively, that are secured to the structure  215  by first and second universal baseplates  212 ,  213  mounted onto the front surface of the structure  215 . 
     The motors  222 ,  232 , such as Oriental Motor model number 51K90A-AFUL, are preferably mounted on the tops of the posts  220 ,  230  to minimize intrusion into the work area and they are controlled and synchronized by a controller unit  210  that is preferably mounted on the side of one of the vertical posts, e.g., the first vertical post  220 . Each motor  222 ,  232  drives a screw  224 ,  234 , such as Roton model number 60404-72, that is engaged by a drive nut  226 ,  236 . The screw  224 ,  234  rests on a bottom bearing plate  229 ,  239  affixed to the bottom of the vertical post  220 ,  230 . As will be described in greater detail below, the drive nut  226 ,  236  travels along the length of the vertical post  220 ,  230  as the motor rotates the screw  224 ,  234 . 
     A top bar link  228 ,  238  is connected to the drive nut  226 ,  236  and extends through a vertical slot (not shown) in the post  220 ,  230  to connect to a respective end of a top bar  240 . A safety net  260  is suspended from the top bar  240  by a plurality of rings  242  spaced at essentially equal distances along the length of the top bar  240 . The bottom of the safety net  260  is secured to the front of the structure  215  by a bottom assembly, preferably a web cable  250  strung between the universal baseplates  212 ,  213 . Those skilled in the art will recognize that alternative methods of securing the bottom of the safety net  260  to the front of the structure  215  may be employed. Preferably, a kick plate  250  extending along the width of the safety net  260  and rising approximately 3 inches above the horizontal surface of the structure  215  is affixed to the net to protect the net from damage caused by shoes and other surface-level objects. A bumper (not shown) extending across the front of the structure and mounted over the vertical posts  220 ,  230  protects the safety system  200  from damage caused by forklifts, trucks, etc. The bumper also provides a pocket into which the net is deposited when the top arm is moved to a lower most position below the horizontal surface of the structure  215 . 
     Each side of the safety net  260  is secured by a plurality of slip guides  248 , spaced at essentially equal distances up each vertical post  220 ,  230  when the top arm  240  is deployed in an upper most position. The safety net  260  is attached to each slip guide  248  using a threaded connector or similar connecting mechanism. Each slip guide  248  is held within the vertical slot of a post  220 ,  230  by a press-fitted dowel or similar retaining mechanism. 
     Perspective, front and top wireframe views of the first vertical post  220  are illustrated in FIGS. 9A-9C, respectively. Those skilled in the art will recognized that the second vertical post  230  is simply a complementary version of the first vertical post  220  and the following discussion therefore applies equally to that post. As illustrated in FIG. 9C, the drive screw  290  is disposed within a modified channel of an extrusion  292 , such as 80/20 model number 1515. The outer wall of the extrusion proximate to the drive screw channel has been machined, as illustrated in FIG. 9D, so that the drive screw  290  may be disposed within the channel. The extrusion  290  is mounted on the interior wall of the post  220  opposite to the vertical slot  221  through an upper extrusion mount  294 , a center support (not shown) and a lower extrusion mount (not shown). 
     The drive nut  226  partially wraps around the extrusion  292  so that screw/bushing pairs (not shown) disposed into tapped holes  226 A from the inner side extend into side extrusion channels to guide and retain the drive nut  226  as it travels along the length of the modified extrusion  292 . The inside surface of the drive nut  226  abutting the drive screw channel of the extrusion  290  includes a pocket into which a nut insert  227  is mounted. The nut insert  227 , typically a removed portion of a standard nut, has a threaded pattern complementary to the threads of the drive screw  290  so as to engage the drive screw  290  when the drive nut  226  is placed onto the modified extrusion  292 . 
     The drive nut  226  includes additional tapped openings  226 B for receiving screws for attaching the top bar connector  228 . The motor  222  is mounted on a motor mount  223  installed on the top of the vertical post  220  and the motor shaft  222 A is in mechanical communication with the drive screw  290  via a spider coupling  291 . 
     A block diagram of the electronic circuitry of the motorized safety system  200  is illustrated in FIG. 10. A DC power supply  1010 , a radio-frequency (RF) receiver  1020 , a micro-controller  1030  and a relay switch  1040 , inter alia, are housed in the controller unit  210  mounted on one of the vertical posts  220 ,  230 . Motor operation is preferably under remote control via a hand-held device (not shown), such as Visitect Inc. model number RF304XT, which may be capable of controlling a plurality of systems at distances up to 250 feet, although local control may also be employed. The user can specify the speed and direction of the travel of the top arm  240  through the hand-held device which modulates this control information onto an RF transmitted signal. The RF receiver  1020 , such as Visitect, Inc. model number RF304RM, detects and demodulates the transmitted signal and sends the control information to the micro-controller  1030 . 
     The micro-controller  1030 , such as Aromat micro programmable controller model number FPO-C14RS, generates motor drive and directional (CW/CCW) signals for each motor  222 ,  232 . These signals are fed to the solid state relay  1040 , such as CRYDOM TD2420Q, to control application of the AC line voltage to the motors  222 ,  223 . The micro-controller may provide an audio warning via a speaker  1236  and/or a visual warning via a flashing light  1238  when the top arm  240  is moving or when the top arm  240  is in a lowered position. 
     First and second upper limit micro-switches  1232 ,  1332  and first and second lower limit micro-switches  1234 ,  1334  are mounted at the tops and bottoms, respectively, of the first and second vertical posts  220 ,  230 . A micro-switch engages when it comes into contact with the drive nut  226  and thus serves to limit the distance of drive nut travel. The micro-controller  1030  monitors the micro-switch signals and turns off the motors when the top arm  240  reaches either the upper or lower limits. 
     In the event of an electrical fault or power outage, the motorized safety system  200  may be placed in manual override mode wherein the motors are de-mounted and a wrench or similar tool is used to rotate the drive screws. 
     Those skilled in the art will recognize that the structural components composing the motorized safety system  200  may be fabricated from aluminum or other suitable materials, such as steel, bronze or plastic. 
     Having described preferred embodiments of the invention it will now become apparent to those of ordinary skill in the art that other embodiments incorporating the concepts of the present invention could also be utilized. Accordingly, it is submitted that the invention should not be limited to the described embodiment but rather should be limited only by the scope and spirit of the appended claims.