The Bommer yoke-spring hinge is also made as illustrated in [Fig. 21]. This yoke hinge consists of two single-acting hinges hung right and left of the same partition on one box flange, the yoke or box flange being constructed as shown at a. As the box flange of this spring is not adjustable, the exact thickness of the marble, or partition, and the door must always be stated in ordering these hinges.
The single-acting spring hinges with clamps, as just described, are fastened to the marble partitions separating water-closet compartments by means of bolts having capnuts, as shown at [b, Fig. 21], and are thus secured firmly in position. Special single-acting hinges may be obtained with a reverse spring that can be regulated to hold the door partly open, instead of in a closed position.
28. Double-Acting Hinges.—The double-acting hinge is similar in construction to a single-acting hinge, except that it is arranged so that the door can swing both ways. These hinges are combined in one piece of hardware, as illustrated in [Fig. 22]. Such hinges are much heavier and more costly than the single-acting hinge, and they are generally used for entrance doors of hotels and public buildings, and for doors between kitchen and pantry or dining room in private residences, where a door that will swing both ways and return to a closed position is desirable. The double-acting hinge is usually subjected to excessive wear and strain. Care should therefore be exercised in selecting this type of hinge; also, in determining the size, it is better to have a hinge slightly larger than required rather than one that is too small. While double-acting spring hinges made of cast-iron may be obtained, those of the latest manufacture are of steel. They may also be procured in brass or bronze, and of any desired finish to match the fixtures and other hardware.
Fig. 22
Fig. 23
In [Fig. 23] is shown another type of double-acting spring hinge that is not so compact as those illustrated in [Fig. 22]. This hinge, as shown, is operated by a coil spring that fits into a rabbet formed in the two leaves of the spring; thus, the coil is invisible when the door is closed, or in its normal position. This hinge obtains a good purchase on the door and jamb.
29. Floor Hinges.—A device is made for hanging single- and double-acting doors by means of pivots, or trunnions, placed at the top or the bottom. The top pivot is usually inactive; that is, it has no spring or other device, and is simply a trunnion, or pivot, with the necessary plate to engage it fastened to the edge of the door trim. The bottom piece of hardware, on the other hand, is arranged with a pivot and a coil spring, and has various mechanisms for operating the door positively and silently.
In [Fig. 24] is illustrated a single-acting, checking-spring hinge. This spring hinge is known as the Bardsley, and its mechanism, which is enclosed in a cast-iron box, is shown at (a). This box, or case, is set into the floor, the top plate being made flush with the top of the floor, as shown at (b). The operating bar, or pivot, of the hinge has a square end, as shown at a, that engages with the plate secured to the bottom edge of the door, and is connected to the mechanism by means of a crank and connecting link, as at b. After being set into the floor, the cast-iron box, or case, containing the spring, piston cylinder, etc. is filled with oil or other non-freezing liquid, and sealed by means of the top plate c. The action of the door in opening compresses the spring and operates the piston in the cylinder. The spring operating to close the door also moves the piston and forces the oil in the cylinder out through a by-pass, the flow being regulated by the adjusting screws d, which are on a level with the top plate. In this manner, the door is closed surely but gently, from which the hinge derives its name of checking-spring hinge. Hinges of this type can be used without any modification of the door or frame, but are not extensively used on account of their high price and the cost of application.