Patent Application
20090297288
This invention relates generally to restraint barriers and, more particularly, to an apparatus for retracting and storing a restraint chain when not in use.
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.
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.
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.
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.
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.
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.
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.
Referring now to
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.
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.
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.
The chain 13 and its attached counterweight 27 is shown in exploded view in
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.
A description of each section of the chain 13 is shown in Table 1 below.
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.
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.
The chain 13 is shown in the fully retrieved condition in
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.
