Abstract:
A barrier includes a curtain vertically movable between a closed and open position. The curtain is interposed between right and left vertical tracks, which guide the curtain&#39;s movement. A drive unit raises and lowers a right edge of the curtain, while a clever strap system supports the curtain&#39;s left edge. The strap system includes a strap having one end fixed to an upper end of the left track and an opposite end fixed to a lower end of the right track. The strap runs across a leading edge of the curtain while passing across a left side roller and a right side roller mounted to opposite ends of the curtain&#39;s leading edge. The strap runs underneath the left roller to support the left side of the curtain. The strap runs across the top of the right roller to keep the strap from simply dropping out from underneath the left roller.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    1. Field of the Invention  
           [0002]    The subject invention generally pertains to a movable barrier and more specifically to a barrier adapted for various uses including, but not limited to, use as a door, machine guarding, and welding flash shield.  
           [0003]    2. Description of Related Art  
           [0004]    At some work centers, various barriers are often used for protecting nearby personnel from the hazards of moving or otherwise hazardous machinery and materials. Examples of such hazards may include, but are not limited to, large or fast moving parts traveling along a conveyor, machining centers throwing chips or coolant, welders emitting eye-damaging light, power washers spraying water, presses, punches, and brakes. If periodic access to such work centers is needed, the protective barrier may be designed with a feature that allows the barrier to be readily moved. For example, the barrier may include a panel that swings or otherwise moves between an open and closed position.  
           [0005]    However, moving a panel to its open position may place the panel in a location that interferes or creates problems with other operations associated with the work center. If the panel swings open and closed, dedicated floor space may be needed just for the door&#39;s operation. This can be a serious problem in situations where space is limited. Having a vertically moving panel that rises to its open position may solve the problem of limited floor space. However, if the panel rises to its open position, the raised panel may interfere with loading or unloading parts to and from the work center. In some cases, reaching underneath a raised panel may be awkward. Also, there may be insufficient headroom to lift a part up and over the raised panel. If the part is heavy and lifted with a jib hoist, a large heavy load swinging high overhead creates a hazard in itself.  
           [0006]    In many applications, a preferred design would be a panel that opens by descending to a lowered position. Unfortunately, such a panel may be difficult to raise and lower without a drive mechanism operating on both lateral edges of the panel. Such a drive mechanism, if it even exists, may be costly and/or may involve installing an overhead drive shaft. Such a shaft may create some of the same problems associated with a panel having a raised open position.  
         SUMMARY OF THE INVENTION  
         [0007]    In some embodiments, a barrier maintains a movable curtain in a proper orientation by coupling the curtain to two curtain guide members against which a pliable elongate member applies both an upward force and a downward force.  
           [0008]    In some embodiments, the tension in a pliable elongate member horizontally compresses a curtain header.  
           [0009]    In some embodiments, a pliable elongate member that helps support the weight of a curtain passes through a curtain header of the curtain.  
           [0010]    In some embodiments, two pliable elongate members share the load of supporting a curtain&#39;s weight substantially equally, yet the tension in one of the pliable elongate members is appreciably greater than that in the other.  
           [0011]    In some embodiments, a barrier includes a curtain that moves upward from a closed position to an open position.  
           [0012]    In some embodiments, a barrier includes a curtain that moves downward from a closed position to an open position.  
           [0013]    In some embodiments, to help maintain a curtain in a proper orientation, a pliable elongate member extends above and below a leading edge of a curtain and transits from one side of the curtain to an opposite side.  
           [0014]    In some embodiments, a barrier is at times inhibited from opening by coupling the barrier&#39;s curtain to two pliable elongate members, which are wrapped in opposite directions around a powered drum.  
           [0015]    In some embodiments, a barrier is inhibited from opening upon losing tension in a pliable elongate member that was intended for supporting the weight of the barrier&#39;s curtain.  
           [0016]    In some embodiments, a barrier includes a curtain holder that helps collect a lower, slack portion of the curtain as the curtain ascends to its open position. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0017]    [0017]FIG. 1 is a schematic illustration of one embodiment of a barrier with its curtain lowered to an open position.  
         [0018]    [0018]FIG. 2 is a schematic illustration of the barrier of FIG. 1, but shown with its curtain at an intermediate position.  
         [0019]    [0019]FIG. 3 is a schematic illustration of the barrier of FIG. 1, but shown with its curtain raised to a closed position.  
         [0020]    [0020]FIG. 4 is similar to FIG. 2, but of another embodiment of a barrier.  
         [0021]    [0021]FIG. 5 is a schematic illustration of yet another embodiment of a barrier with its curtain raised to an open position.  
         [0022]    [0022]FIG. 6 is a schematic illustration of the barrier of FIG. 5, but shown with its curtain at an intermediate position.  
         [0023]    [0023]FIG. 7 is a schematic illustration of the barrier of FIG. 5, but shown with its curtain raised to a closed position.  
         [0024]    [0024]FIG. 8 is a cross-sectional view taken along line  8 - 8  of FIG. 6.  
         [0025]    [0025]FIG. 9 is a cross-sectional view taken along line  9 - 9  of FIG. 6.  
         [0026]    [0026]FIG. 10 is a schematic illustration of a barrier including a curtain shown in its closed position and a curtain-blocking device shown in a release position.  
         [0027]    [0027]FIG. 11 is similar to FIG. 10, but showing the curtain-blocking device in a blocking position. 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0028]    A multipurpose barrier  10  includes a curtain  12  that is vertically moveable to an open position (FIG. 1), various intermediate positions (FIG. 2), and a closed position (FIG. 3). The term, “curtain” refers to any sheet that can readily bend and repeatedly recover its original shape. Examples of curtain  12  include, but are not limited to, a pliable sheet of plastic, a pliable sheet of fabric, and an assembly of pivotally interconnected rigid panels. The curtain&#39;s movement allows it to selectively cover and uncover an access opening  14  between two vertical tracks  16  and  18 . Such an opening may simply be a doorway or may provide physical or visual access to an area that at times is preferably shielded or guarded. As curtain  12  opens, the lower portion of curtain  12  may fold upon itself or otherwise gather near floor level  20  where the lower portion of curtain  12  can be stored in some type of container or left exposed, as shown in FIG. 1.  
         [0029]    To guide the curtain&#39;s movement, a leading edge  22  of curtain  12  includes a first end  24  attached to a first curtain guide member  26  and a second end  28  attached to a second curtain guide member  30 , wherein guide members  26  and  30  are constrained to move vertically along tracks  16  and  18  respectively. The tracks and guide members are schematically illustrated to represent any apparatus having an element guided generally along a desired path. Guide members  26  and  30  may each be a trolley with rollers  32  or may be a sliding member that slides along an appropriately shaped track.  
         [0030]    To support the weight of curtain  12 , guide members  26  and  30  are suspended from a first pliable elongate member  34  and a second pliable elongate member  36 , respectively. The pliable elongate members are schematically illustrated to represent all types of pliable elongate members including, but not limited to, a strap, cable, chain, rope, etc. A drive assembly  38  (e.g., a winch, lead screw and nut, pinion and gear rack, piston and cylinder, etc.) is used to raise and lower curtain  12 . In a currently preferred embodiment, drive assembly  38  comprises the second elongate member  36 , wherein elongate member  36  includes a lower end  40  fixed to guide member  30  and an upper end  42  wrapped around and fixed to a powered drum  44 . A drive unit  47  (e.g., a motor) rotates drum  44  either clockwise or counterclockwise to selectively take-up or pay out second elongate member  36 , which in turn raises and lowers second guide member  30  to raise and lower curtain  12 .  
         [0031]    To move first guide member  26  up and down in synchronization with the vertical movement of second guide member  30 , and to maintain leading edge  22  of curtain  12  generally level, first elongate member  34  is installed in such a way as to avoid the need for an overhead cross member extending between the upper ends of tracks  16  and  18 . More specifically, first elongate member  34  includes an upper portion  46  fixed relative to first track  16  and a lower portion  48  fixed relative to second track  18 . An intermediate portion  50  of elongate member  34  runs generally alongside leading edge  22  of curtain  12  and extends between a first rotatable member  52  (e.g., a sheave, drum, wheel, etc.) on first guide member  26  and a second rotatable member  54  on second guide member  30 . Thus, in this embodiment, elongate member  34  is coupled to curtain  12  via rotatable members  52  and  54  and via curtain guide members  26  and  30 . First elongate member  34  passes underneath rotatable member  52  and over second rotatable member  54 , such that the weight of curtain  12  and guide members  26  and  30  places first elongate member  34  in tension. This tension exerts an upward force  56  (FIG. 2) against first rotatable member  52 , which helps support the weight of first guide member  26  and about half the hanging weight of curtain  12 . The tension in first elongate member  34  also exerts a downward force  58  (generally equal in magnitude to force  56 ) against second rotatable member  54 . Consequently, second elongate member  36  not only supports the weight of second guide member  30  and about half the hanging weight of curtain  12 , but also counteracts the downward vertical component of force  58 . As a result, the tension in second elongate member  36  is appreciably greater than the tension in first elongate member  34 . The term, “appreciably greater” means at least  20  percent greater. In some embodiments, second elongate member  36  has about twice as much tension as first elongate member  34 , even though the hanging weight of curtain  12  is shared about equally between elongate members  34  and  36 .  
         [0032]    The horizontal components of forces  56  and  58  are transmitted through guide members  26  and  30  and rollers  32 , which in turn applies a horizontal force against tracks  16  and  18 . The horizontal forces applied by rollers  32  against tracks  16  and  18  urge the tracks toward each other and subjects rollers  32  to a force that may shorten their life. To minimize this effect, a curtain  60  may be provided with a generally rigid curtain header  62 , as shown in FIG. 4. Curtain header  62  can be a channel, tube, or other structural member that can withstand horizontal compression created by the tension in first elongate member  34  (i.e., compression created by the horizontal components of forces  56  and  58 ). In this way, curtain header  62  can hold two curtain guide members  64  and  66  a certain distance apart from each other without having to rely on the strength and stiffness of tracks  16  and  18 . Curtain header  62  also provides a convenient structure to which curtain  60  may be attached. If curtain header  62  is in the form of a channel or a tube, the interior of curtain header  62  may provide a covered passageway through which elongate member  34  may run.  
         [0033]    In some applications (e.g., when the access opening is a doorway), it may be desirable to have a barrier  68  whose curtain  12 ′ stores in a raised position to keep the floor clear, as shown in FIG. 5. Barrier  68  is also shown in an intermediate position in FIG. 6 and in a closed position in FIG. 7. Many of the parts of barrier  68  are similar in structure and function to corresponding parts of barrier  10  and/or  68 . In particular, a first pliable elongate member  34 ′ (e.g., a fabric strap), a second pliable elongate member  36 ′, a powered drum  44 ′, a first track  16 ′, a second track  18 ′, a first curtain guide member  26 ′, a second curtain guide member  30 ′, a first rotatable member  52 ′, a second rotatable member  54 ′, and curtain header  62 ′ are similar to first pliable elongate member  34 , second pliable elongate member  36 , powered drum  44 , first track  16 , second track  18 , first curtain guide member  26 , second curtain member  30 , first rotatable member  52 , second rotatable member  54 , and curtain header  62 , respectively.  
         [0034]    An upper edge of curtain  12 ′ attaches to an overhead cross member  70  that extends between tracks  16 ′ and  18 ′. A lower edge of curtain  12 ′ connects to curtain header  62 ′. As barrier  68  opens, a lower portion of curtain  12 ′ folds upon itself and collects in one or more curtain holders  72  that are pivotally attached to curtain header  62 ′, as shown in FIG. 8. This curtain gathering process can be facilitated by providing curtain  12 ′ with the added weight and stiffness provided by several curtain stiffeners or bars  74 , which can assume a variety of structures including, but not limited to, rectangular bar stock, round bar stock, or pipes.  
         [0035]    To improve the appearance of barrier  68  when in the closed position of FIG. 7, pins  76 , protruding from tracks  16 ′ and  18 ′, force curtain holder  72  to pivot upward as the holders are lowered between adjacent pins  76 , as shown in FIGS. 7 and 9. As curtain  12 ′ rises from its stored position of FIGS. 7 and 9 to an intermediate position of FIGS. 6 and 8, curtain holders  76  are lifted away from pins  76 . This allows holders  72  to pivot outward to a position where the holders can effectively collect the lower folded portion of curtain  12 ′, as shown in FIG. 8.  
         [0036]    To help inhibit someone from manually forcing barrier  68  open when a drive unit  47 ′ is turned off, drive unit  47 ′ includes a single drive shaft  78  for driving the rotation of both the first powered drum  44 ′ and a second powered drum  80 . The structure and function of first drum  44 ′ is similar to that of first drum  44  of barrier  10 . With second drum  80 , a third pliable elongate member  82  includes a lower section  84  fixed relative to second curtain guide member  30 ′ and an upper section  86  fixed to and wrapped around second drum  80 . An intermediate section of third elongate member  82  passes underneath a rotatable member  88  that is at a generally fixed location near the bottom of barrier  68 . Elongate members  82  and  36 ′ wrap around their respective drums  80  and  44 ′ in opposite directions. So, as shaft  78  rotates, lower section  84  of elongate member  82  and a lower end  40 ′ of elongate member  36 ′ move in the same direction with second curtain guide member  30 ′. Consequently, when shaft  78  is not rotating, lower section  84  of elongate member  82  and lower end  40 ′ of elongate member  36 ′ help hold second guide member  30 ′ generally fixed, thus helping to inhibit someone from forcing barrier  68  open when drive unit  47 ′ is turned off. In cases where elongate members  36 ′ or  82  are a strap that overlaps itself upon wrapping about a drum, such elongate members may be provided with a spring or some other yielding member that compensates for a drum&#39;s effective change in diameter caused by varying the number of strap layers around the drum as the drum rotates.  
         [0037]    As an alternative to having a second powered drum for inhibiting someone from forcing a barrier open, a barrier  186  can be provided with a curtain-blocking device  188 , as shown in FIGS. 10 and 11. Device  188  includes a pawl  90  pivotal about a pin  92 . A tension spring  94  urges pawl  90  to pivot clockwise (as viewed in the drawing figures). An upper end  96  of pawl  90  is connected to a pliable elongate member  36 ″. When the weight of a curtain  12 ″ holds elongate member  36 ″ taut, the tension in elongate member  36 ″ holds pawl  90  in a release position, as shown in FIG. 10. If someone begins manually lifting curtain  18 ″, elongate member  36 ″ relaxes, which allows spring  94  to pivot pawl  90  to a blocking position, as shown in FIG. 11. In the blocking position, upper end  96  of pawl  90  engages a fixed stop  98  that inhibits further manual lifting of curtain  12 ″.  
         [0038]    Although the invention is described with reference to a preferred embodiment, it should be appreciated by those skilled in the art that various modifications are well within the scope of the invention. For instance, although curtain  12 ′ of barrier  68  in FIG. 7 is not shown completely down against the floor in the closed position, modifying barrier  68  to provide a tightly closed position would involve modifications that would be obvious to those skilled in the art. For example, a rigid panel could simply be attached to the underside of curtain header  62 ′ to fill any gaps between header  62 ′ and the floor. To show more clearly the operation of various barriers, several barrier components are shown positioned where they are visible rather than hidden within a track. For example, pliable elongate members, trolley rollers, rotatable members, curtain guide members, curtain holders, and curtain-blocking devices have been shown extending into the access opening or doorway. It should clear to those skilled in the art, that such components can be readily contained within the tracks. Moreover, the disclosed barriers can be provided with various compliant seals to seal air gap, such as between the curtain and the adjacent tracks. Therefore, the scope of the invention is to be determined by reference to the claims that follow.