The cold air constantly entering through the outside doors of large buildings during the winter months, has heretofore been a serious problem for the architect to solve. The entrance of snow, rain and dust during wind storms is almost equally as troublesome. To meet these objections as much as possible, vestibules have hitherto been provided with outer and inner doors, and where there is not space for the vestibule, "storm houses," forming a temporary vestibule are often put up in the fall and taken down in the spring. These precautions, however, have been found to only partially accomplish their purpose, and the great necessity of a device for public or semi-public entrances, that would more efficiently keep out the cold and dust, led to the invention of the "revolving door," which was first successfully introduced and operated in the year 1888.

The Franklin Institute of Philadelphia, after an exhaustive investigation and severe tests, awarded their highest medal to T. Van Kannel, the inventor and promoter of revolving doors. Letters patent were taken out by the inventor, and all of the important patents on revolving doors are now exclusively owned and controlled by the Van Kannel Revolving Door Company, of New York.

At the present time revolving doors are looked upon as next to indispensable for office buildings, hotels and other places where large numbers of persons pass in and out, and where it is desirable to keep out all wind, snow, rain and dust. They may be seen in operation in most of the principal cities of this country and Canada, and also in several European cities.

The standard revolving door consists of a circular vestibule 7 feet in diameter and 7 feet high, inside. The front and back of this vestibule are open, as shown in the illustrations, but the top or ceiling, and the two circular walls form a complete enclosure. The revolving portion of the structure consists usually of four wings, which are joined at the centre and pivoted at the top and bottom. The upper pivot is suspended by a conical head, resting on a self-adjusting bearing in a four-wheeled truck, running in two strong channel irons placed on top of the ceiling. The wings are joined at the centre in such a way that they may be instantly folded flat on each other and moved aside in a few seconds of time.

The outer edges of each wing have a moulded rubber safety strip with 2 inches projection to prevent any pinching of hands and ♦ fingers, and rubber strips are also placed at the bottom, touching the floor, and at the top, making contact with the smooth ceiling, thus forming a perfect protection from wind and dust at all positions of the wings.

The operation of the door is indicated by the four diagrams, Fig. 510.

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Fig. 510.

Diagram A represents the door in full operation, permitting persons to pass in and out, and at the same time excluding the wind, two of the wings being in contact with the walls in whatever position the revolving portion may assume. The wings may be folded flat on each other in the centre of the vestibule, as at B, and secured by means of bolts, thus affording two passageways. Should a full opening be desired, the wings may be instantly pushed aside and held in the position shown at C. Diagram D shows the wings folded across the entrance, in which position they may be securely locked.

It is claimed that the revolving door has a greater capacity than any other storm door in proportion to the space it occupies. All confusion and collision are avoided, and the passage of people in and out (at the same time) is uninterrupted.

The door cannot be left open, blown open or slammed.

The greatest advantage from a commercial point of view, is probably the saving in fuel which it effects.

The arrangement of the door in the entrance to a building may be varied considerably to suit the available space and the character of the building. Figs. 511-515 show various arrangements that have been found very satisfactory, and several others are illustrated in the catalogue of the manufacturers. For the arrangement shown in Fig. 511, the minimum width between the corridor walls or partitions, to accommodate the standard (7-foot) door, is 7 feet 6 inches, but in case of necessity a smaller vestibule may be used requiring a width at W of only 6 feet 5 inches. With the 7-foot door, the width of the opening A is 5 feet, and in the 6-foot door, 4 feet.

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Fig. 511.

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Fig- 514.

Fig. 515.

When the width of the doorway is greater than that of the revolving door, the space may be filled by glazed or solid panels or mould-ings.

In several instances the door has been placed outside of the building, simply reversing the plan, Fig. 512. For banks, etc., where it is desirable to retain the outside doors for greater security at night, the revolving door may be placed as in Fig. 513, and the permanent doors X, X, held open against the door jambs, during the day, or while the revolving door is in use,

Fig. 516.-Van Kannel Revolving Door*.

Fig. 514 shows a very desirable arrangement for retail stores, in which the circular walls of the revolving door also form the end walls of the display windows, taking up but little space and producing a handsome effect.

Fig. 515 shows a double set of doors as placed in the entrance of a large office building.

Fig. 516 shows the appearance of the door and vestibule from the outside when arranged as in Fig. 511. Transom lights are usually-placed above the top of the vestibule or door.

Special revolving air lock doors are made to be placed between the kitchen and dining room of hotels and restaurants. Also for hospitals, factories, libraries and all places where it is desirable to keep out fumes, odors, dust or noise.

In many buildings a specially constructed revolving door may be used to cut off one room from another to prevent the passage of flames in case of fire, and also to prevent a draught; in fact there are many places besides those mentioned, where the revolving door can be used to great advantage.