It is sometimes necessary to close wide openings between adjacent rooms with folding doors. The common custom in such cases has been to make the doors or folds which close the opening of uniform width, the outer doors being hung to the jambs and carrying the adjoining folds as with shutters. Where one door is hung to another, however, the doors are quite sure to sag, and to make the doors work easily a heavy castor should be put under the carrying edge of each fold, so that the door may roll on the floor as it swings. For closing wide openings, separated by posts, the author has found it an advantage to divide the doors, as shown in Fig. 364, the folds next the jamb being but one-half the width of the middle folds. By making the outer folds narrow there is not the leverage on the jamb hinges that there is with wide doors, and the doors are not so apt to sag. When divided in this way the doors do not come as much in the way when open as they do when all the folds are of equal width.
(plated as desired), and 5 or 6 inches high, but not more than 4 inches wide for a 1¾-inch door.
When there is room for a track above the doors, they may be suspended at their centres by swivel carriers rolling on an overhead track the same as used for parlor doors, the doors turning on the swivel as they are folded, as indicated in Fig. 365. The
Coburn Trolley Track similar to the one shown in Fig. 341, screwed to the face of the door, instead of butts, and at least three hinges to a fold.
Manufacturing Co. make a special carrier (Fig. 366) for this purpose.
When doors are hung as in Fig. 365 it will be better to use hinges
Fig. 366 - Coburn Swivel Hanger ; Ball Bearing.
Balanced Doors. - The outside doors of freight elevator shafts and also of freight sheds are usually hung to slide up and down, as there is not generally room for swinging doors. When the expense will permit, self-coiling steel shutters or doors are considered as the best means of closing such openings, but for ordinary mercantile buildings, large single doors balanced by weights are more commonly used.
Balanced doors should preferably be hung from overhead pulleys, as in Fig. 366a, with either metal bands or sash chains for connecting the weights with the door. The Gardner Sash-Balance Co. makes an 8-inch roller bearing overhead pulley, by means of which, and their metal sash ribbon, doors weighing up to 500 pounds may be raised or lowered with ease.