Abstract:
A temporary barrier chain for a loading dock door opening includes a vertical orientated storage tube on one side of the opening and a retainer on the other side thereof, and a counterweighted chain extending from inside the storage tube to a retainer on the other side of the opening, with the chain being comprised, at least partially, of successively lighter weight sections toward the retainer end such that the combined weight of the counterweight and suspended chain within the storage tube will cause the chain to be automatically retrieved into the storage tube when released from the retainer.

Description:
TECHNICAL FIELD 
       [0001]    This invention relates generally to restraint barriers and, more particularly, to an apparatus for retracting and storing a restraint chain when not in use. 
         [0002]    For purposes of safety and possibly other reasons, it has been desirable to temporarily close off an area from entry or exit with a barrier such as a belt or chain being strung across an opening to temporarily close it off but later allow the belt or chain to be removed and stored in a housing to clear the opening for entry or exit. An example of such a device is a belt which has traditionally been used at the door opening of a warehouse dock. Although the safest approach is to have a solid door that is open only at times when the truck is backed-up to the opening and closed at all other times, there are occasions when this is not practical, such when there is a need for ventilation in the warehouse, for example. Thus, a belt across the opening provides a visual indication that the space is not open for use and that caution should be taken when one is in that vicinity. Provision is then made for selectively retracting the belt by way of spring loaded mechanism to remove the strap from the vicinity of the opening. Such an apparatus is described in U.S. patent application Ser. No. 11/471,803, filed on Jun. 21, 2006 and assigned to the assignee of the present application. 
         [0003]    A disadvantage to such a retraction system is the complexity and cost. Further, although the belt is normally designed to withstand a force such as might be experienced when struck by a person, for example, there are some installations where a greater robustness is desired so as to assure the user that the strength of the barrier will not be exceeded and that it will remain durable for long periods of use. This additional strength and durability can be obtained by the use of a steel chain. However, such a chain cannot easily be wound up or retracted by way of a spring loaded mechanism. 
         [0004]    One approach to solving the chain storage problem is to provide a counterweight on the storage end of the chain such that the free fall of the counterweight will act to retract the chain into a tube. However, in order to accomplish this, it is necessary to have a cavity of substantial depth under the floor in order to accommodate the free fall of the counterweight. 
         [0005]    There is therefore a need for a method and apparatus for retracting and storing a restraint chain without the need for a cavity under the floor. 
       DISCLOSURE OF THE INVENTION 
       [0006]    Briefly, in accordance with one aspect of the invention, the barrier chain comprises a plurality of interconnected sections which are progressively smaller as they extend away from counterweight such that the weight of the chain exerting gravitational pull within the storage trunk is greater than the weight of the extended chain from the mouth of the storage trunk to the floor. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0007]      FIG. 1  is a perspective view of the present invention as installed in a loading dock door opening. 
           [0008]      FIG. 2  is a perspective view of the chain and storage portion thereof. 
           [0009]      FIG. 3  is an exploded view of the chain portion thereof. 
           [0010]      FIG. 4  is a perspective view of the chain portion as placed in the stored position. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0011]    The invention is shown generally at  10  as applied to an opening  11  in a loading dock  12  when a door is in the open position. Its purpose is two fold: that of providing an indication to people in the vicinity that they should be aware of the open door condition and secondly, to act as a barrier to people that may be in the vicinity. 
         [0012]    The invention  10  includes a chain  13  which extends across the opening  11 , a retainer bracket  14  secured to the wall  16  on one side of the opening  11 , and a storage tube  17  secured to the wall  18  on the other side of the opening  11 . The storage tube  17  is designed to store the chain  13  in its inner space during periods in which the chain is not in use. To extend the chain as shown, the chain is simply pulled out of the storage tube  17  with its one end being mechanically secured in the retainer bracket  14  as shown. The chain  13  is so sized and placed that the center of the sag is 42-48 inches above the top surface of the loading dock  12 . Thus, the chain  13  is generally about 10 feet long, with the two ends thereof being at about 51 inches above the top surface of the loading dock  12 . It should also be of sufficient strength to sustain a force of 300 pounds. 
         [0013]    Referring now to  FIG. 2 , the storage tube  17  is shown to include three serially and integrally connected portions including, a straight portion  19 , a 90° elbow  21 , and a bell  22  with an orifice  25 . The inside diameter of those members is 2.25 inches. However, that size can be varied to accommodate the particular installation, keeping in mind that the storage tube  17  must be of sufficient strength to maintain its vertical position for years of use without being bent over or broken. Further, it must be of a size to accommodate the storage of all of the chain in a manner as described hereinafter. The storage tube  17  is preferably made of a steel material, but other suitable materials may also be used. 
         [0014]    At the base of the straight portion  19  is an L-shaped bottom bracket  23  that is used to attach the storage tube  17  to the wall and/or the floor. A top bracket  24  surrounds a top portion of the straight portion  19  and is used for attachment of a top portion of the storage tube  17  to the wall. In this way, a storage tube  17  can be located entirely above the floor, and can therefore be installed in an existing warehouse without disturbing the floor. Alternatively, if installed in a building under construction, it may be constructed so as to extend into the floor for stability purposes, and if so, either the bottom bracket  23  and/or top bracket  24  may be omitted. 
         [0015]    The bell portion  22  provides for an expanded diameter as it extends away from the elbow  21 . It is desirable for facilitating the easier return of the chain  13  to the storage tube  17  when the chain is being stored. 
         [0016]    A bolt  26  is passed through the straight portion  19  near its upper end after the counterweight has been installed in the storage tube  17  so as to retain the counterweight  27  within the storage tube  17 . This function can also be performed by “necking down” the tube at the appropriate position and then inserting the counterweight from the bottom of the tube during the installation phase. 
         [0017]    The chain  13  and its attached counterweight  27  is shown in exploded view in  FIG. 3 . The counterweight  27  is of any suitable shape, such as a cylindrical shape as shown, and is of a weight which will cause the chain to be retrieved when the counterweight  27  descends to the bottom of the storage tube  17 . The particular one shown is about 4-5 inches tall, 2.25 inches in diameter and weighs about 5 pounds. It is secured to the first section  28  of the chain  13 . 
         [0018]    The chain is comprised of five sections  28 ,  29 ,  31 ,  32  and  33 , with interconnecting S hooks  34 ,  36 ,  37  and  38  as shown. As will be seen, the section  28  and the section  31  are comprised of the same type of chain (i.e. 5/16 inch steel chain), and the section  29  is comprised of a lighter weight chain that merely serves to connect the sections  28  and  31  but plays no active role in the weighting algorithm in order to allow for automatic retrieval of the chain  13 . However, it will also be seen that the section  31 ,  32  and  33  are of decreasing weight such that, once the counterweight falls to the bottom of the storage tube  17 , the weight of the chain suspended from the top of the storage tube (i.e. from the bell  22  to the pile of chain piled at the bottom of the storage tube  17  is sufficient to cause, by its gravitational pull, the remaining portion of the chain  13  to be drawn into the storage tube  17 . 
         [0019]    A description of each section of the chain  13  is shown in Table 1 below. 
         [0000]    
       
         
               
               
               
               
               
             
               
               
               
               
               
               
               
             
           
               
                 TABLE 1 
               
               
                   
               
               
                 Section 
                 Type 
                 # of Lines 
                 Length 
                 Weight 
               
               
                   
               
             
             
               
                   
               
             
          
           
               
                 28 
                 5/16 steel welded 
                 10 
                 13.32 
                 in. 
                 1.32 
                 lb. 
               
               
                 29 
                 2/0 twist machine 
                 23 
                 18 
                 in. 
                 13 
                 lb. 
               
               
                 31 
                 5/16 steel welded 
                 12 
                 15.88 
                 in. 
                 1.45 
                 lb. 
               
               
                 32 
                 2/0 twist machine 
                 48 
                 35 
                 in. 
                 .9 
                 lb. 
               
               
                 33 
                 #3 twist machine 
                 60 
                 36 
                 in. 
                 .4 
                 lb. 
               
               
                   
               
             
          
         
       
     
         [0020]    Thus, considering that the distance from the bottom of the storage tube  17  to the center of the bell  22  is 52 inches, when the counterweight  27  reaches the bottom of the storage tube  17  the sections  28  and  29 , as well as substantially all of the section  31 , will be extended between the counterweight  27  and bell  22 . Thus, the weight of the section  31  will exceed the weight of those sections  32  and  33  combined, and its gravitational pull will cause the sections  32  and  33  to be drawn into the bell  22 . As the section  31  falls downwardly and tends to pile up on the chain sections below, its gravitational pull is gradually reduced, but at the same time, there are portions of the section  32  which have now been drawn into the storage tube  17  and which are acting to further pull the chain into the storage tube  17 . In this way, with the aid of the counterweight  27  and the weight of the suspended chain within the storage tube  17 , there is a constant bias for the chain  13  to be automatically retrieved once it is disconnected from the bracket  14 . 
         [0021]    Connection of the chain  13  to the bracket  14  is by way of a T-clip  39  which is attached to the section  33  by way of connecting link  41 . 
         [0022]    The chain  13  is shown in the fully retrieved condition in  FIG. 4  wherein the T-clip  39  is against the bell  22 . When it is desired to again extend the chain across the opening, one simply needs to pull the T-clip and the attached chain to the extended position and again attach the T-clip to the bracket  14 . 
         [0023]    While the present invention has been particularly shown and described with reference to the preferred mode as illustrated in the drawing, it will be understood by one skilled in the art that various changes in detail may be effected therein without departing from the spirit and scope of the invention as defined by the claims.