Friday, January 22, 2016


Post 135 ⇒ by Gautam Shah

Doors have THREE categories of HARDWARE:
1 BASIC HARDWARE attaches a shutter directly or through a frame to an opening or doorway.
2 SECONDARY HARDWARE provides control on the movement of a door.
3 APPENDAGES OR ATTACHMENTS that endow various types of functionality.

BASIC HARDWARE for doors consists of shutter hanging mechanisms. First doors had shutters of stone, wood, grass or reeds, leaves, hides or skins, woven mats and fabrics. The shutters, in order to open and close the opening, were made to swing, fold, collapse, slide or roll up.

STRAPS: The primitive age door-shutter holders were straps of leather, ropes, vines, and threads, and fabrics. Modern age doors have of synthetic materials (plastics and composites) used as flexible hinges. Straps are still used in some conditions where metal friction is likely to cause sparks of erosion (petroleum solvent plants and cordite plants), but are made from new technology materials such as woven Fibre glass, Teflon, Cavalar, and carbon fibre composites.
PIVOTS: Early age large size doors and of heavier materials, such as stone, cast bronze and massive wood required pivots. Ancient doors were primarily hung by pivots, formed as a protrusion of the door material at the top and bottom as the hanging edge of the stile. The pivot rotated in sockets in the lintel and sill or thresholds in the floor. The pivots and the sockets, both of them were later encased with harder material such as granite, basalt, hard woods, bronze, iron, etc. Later day pivots were lined with metal sheaths. The other ends of the pivot, the nodes, were inserted into hard stone holes at floor and ceiling levels. Problems with pivot mechanisms were many: pivot nodes wore out fast -lowering and often tilting of the shutter, pivots broke frequently making shutter useless, and replacement of a worn or broken pivot requires a lot of structural changes. Pivots of cast bronze or iron were a better option, but required special joining with wood and more so with stone shutters.
Bank vault door with shelf Pivot hinges > Wikipedia image > WinonaSavingsBankVault.JPG by Jonathunder

Pivots are fixed on the top and bottom corners, either exterior or interior face a door shutter, and also on the shutter side from a mid point to the corner of the shutter. Pivoted doors nominally open inside, but can as well swing in both directions. For pivoted doors no frame is necessary, however a projected edge of the portal frame can seal the edges and acts as a shutter stop. Pivots were difficult to insert, repair or replace, making way for development of hinges, and to a small extent sliding channels. Pivots fixed to side walls or frames are called pivot hinges or double-acting floor hinges, because opening movement is allowed in both directions as similar to hydraulic floor pivots (used for glass doors in modern buildings).
Notre Dam door hinges Flickr image by Michael Rymer
A hinge is component that ‘attaches one side edge of a door shutter to the frame, while allowing the other edge to swing from it’. A hinge can also be an arrangement, type of bearing that connects two solid objects allowing a limited angle of rotation between them. Conceptually two objects connected by a hinge ‘rotate relative to each other about a fixed axis of rotation (the geometrical axis of the hinge)’. Hinges consist of a pair of plates, each with a set of open cylindrical rings, the knuckles, formed out of the plates, or attached to them. The knuckles of the two plates are offset from each other and mesh together. A hinge pin is then placed through the two sets of knuckles to form a single unit.
One door shutter usually requires minimum two, or more hinges. Nominally three bands (horizontal members of a panelled door) have three hinges, of which the top hinge is in ‘pull out stress’, the bottom hinge is in ‘push in stress’ due to the cantilever action of the shutter and the middle hinge is in ‘neutral stress’ state. All three hinges have downward gravity bearing.
Butt or mortise Hinges are inset -mortised into the door stile and frame. The hinge is fixed with its pin section (cylinder) remaining out of the door face, to allow 180° of opening, i.e. the shutters can rest on the side of the door opening. Sometimes mouldings over shutters, frames or casings, however, interfere in the resting of the shutter, and for such conditions hinges flanges of larger width are used or fixed with greater outward projection of the pin section. Flanged Hinges formed of steel, bronze and brass alloys are being used since middle ages. Hinges were viable with smaller and lighter shutters. In case of pivots the bottom one carried the load of the shutter, whereas the top pivot was mere holding element. But in case of hinges, all of them shared the carriage of loads.
Early hinges began as a wall-hung or shelf-pivots, where the pivot-pin was on a small shelf, hung off the sides, and the girth or ring was fixed with the shutter. The wall-hung pivots were made of wrought iron or bronze. These were much easier to insert after the masonry work, and later, to repair or replace. Early shelf-pivots became long armed hinges, and now have become an expression of the medieval door.
Modern hinges are available of brass, bronze, mild steel, stainless steel, ABS and polypropylene plastics, carbon composites, etc. Most of the commercial hinges are made of several components (such as flanges, flange edge liners, pin, pin cylinder liners, coil springs, hydraulic cylinders, etc.), and these are again composed of many different materials. Hinge like movement systems are also employed in many types structures and movable bridges. In biology many body joints function as hinges.
BUTT OR MORTISE HINGES: These are also known as shangles in old Tudorian English. Butt or mortise hinges are made of hard wearing and stiff materials. The pin is made of stainless steel, carbon steel, nylon and Teflon, some of these materials do not require any lubrication.

FLUSH HINGES: These hinges are surface-mounted and do not require a recess to be cut. These are not as strong as butt hinges, but can be used for lightweight doors and small box constructions.
KNUCKLE HINGES: These are flush butt hinges, fixed over the face of the door and its frame, and so not mortised. The pin cylinder or the knuckle is designed to be visible.
PARLIAMENT OR BUTTERFLY HINGES: These were known as Dovetail hinges and used for cabinets from the 17th C till 18th C. The size and form of these hinges vary depending on the use, material and manufacturer. Very small ones are used for jewellery boxes or caskets and large ones used in public buildings (and so the name -parliament). For deep-set door frames Parliament hinges park a deep-set shutter along the corridor -at an opening angle of 180°.
STRAP HINGES: A strap hinge has a small height but a wider flange that accommodates two or three screws in a row on each flange.
BACK FLAP HINGES: Back flap hinge is exactly the opposite version of the strap hinge. It has a squarish flange (height and width are nearly equal) Both are used in furniture items.
Living Hinge laser cut from Plywood > Wikipedia image by Autopilot
LIVING HINGE: A living hinge is a thin strip moulded into a plastic part to create a line along which the part can bend. If properly designed and made, its ‘closing and opening capacity lasts for more than a million cycles without failure’. It is a thin flexible hinge with flexure bearing. It is formed during the injection moulding process for plastics or a composite of it. Such hinges are used on lunch boxes and shampoo or hair oil bottles, and are formed of deform-able plastics such as polyethylene, PVC, polypropylene, etc.
PIANO OR CONTINUOUS HINGES: These hinges are long enough to cover the entire length of the shutter, so support the shutter well against warping. Very thin sections of shutter boards (non panelled, without frames) require such hinges. These are used in cupboards, pianos, baueras, and desk top shutters.
Nintendo Hinge > Wikipedia image by Evan-Amos
 ■ INVISIBLE HINGES: These are used for joining two shutters. These are fully mortised as centred on the door shutter’s face. Door shutters seem like units of wall panelling as hinges are completely invisible.
CONCEALED HINGES: These are not seen outside a closed shutter, such as for furniture doors. These are sometimes spring loaded with self-closing features, and with or without a dampening system (slowing down the closing speed during the last few degrees). They are made of 2 parts: One part is the hinge cup and the arm; the other part is the mounting plate. The concealed hinges come in two sizes, 25 mm and 36 mm. The hinge once fitted is adjustable to correct the door alignment and planner straightness. These hinges are designed for use with chipboard and MDF.
Concealed Hinge > Wikipedia image by Julius Blum GmbH

H HINGES: These are shaped like an H, and used on the flush mounted doors. Small H hinges (75 to 100 mm) are used for cabinets and larger hinges (150 to 175 mm) are used for passage doors or closet doors. Large HL Hinges were common for passage doors, room doors and closet doors in the 17th to 19th C. On taller doors H hinges were occasionally used in the middle along with the HL hinges at top and bottom.
Eastlake Style Door Hinge > Wikipedia image by Found5dollar
BARREL HINGE: These Liftoff butt hinges have two components. The bottom section has a cylinder or pin like projection over which a top hollow ring or cylinder is set. The shutter can be lifted off its position for servicing, cleaning etc. These are used in kitchen cabinets.
Lift off Hinges for Cabinets
LOOSE PIN HINGES OR BALL TIPPED HINGES: These serve the same purpose as the liftoff butt hinges. A removable pin holds two halves of the hinge knuckles together.
STOPPED HINGE: This is like any butt hinge but a square cut projection on the cylinder side of one flange restricts the opening of the shutter to 90° only.
DOUBLE ACTION HINGE: These have three flanges. The middle flange has hinged flanges on either side. The edge flanges are mortised into the side of the shutter, but the middle flange remains off the sides. The assembly leaves a space between the door shutter and its frame or other shutter. The hinge allows the shutter to open in both directions. Such hinges are used in saloon and bar doors.
Double action Hinge for Saloon and Bar doors
 ■ DOUBLE ACTION SPRING HINGES: These are used on half height saloon doors. The hinge allows the shutter to open in both directions, but being a spring loaded mechanism, the closing action is automatic. In another version of such a hinge, it is fixed to the frame, and the other flange in the form of an arm has a roller at the edge. The shutter is often provided with a plate or channel for the roller arm to slide.
UNEQUAL FLANGE HINGES: These have unequal flanges in terms of width. A thin shutter has thin flange compared to wider flange for the frame side. Unequal hinges also have a greater length of flanges to compensate the reduced width of the flange.
FRICTION STAYS: Friction stays are fitted at top and bottom edges of the surface, and used on French doors. Such hinges allow a door to stay-put in its position in spite of the heavy winds, and so prove an ideal fixture on windy faces such as sea shores, mountain valleys etc. The hinge requires framing at least at the top and bottom, making it better suited for windows. It has a sliding channel within which a component fixed to the bottom of the shutter, for converting the rotational movement of opening into a linear thrust, through a collapsible triangular arrangement.
ASKEW OR VERTICALLY MISALIGNED PIVOTS OR HINGES: Fort doors had askew or vertically misaligned pivots or hinges, so in case of an emergency the door would be released from its catch to close fast, and automatically. This mechanism required greater manpower to open it and a stronger stay to keep it open. Similar systems are employed in modern hospitals, class rooms, garden, and toilets doors, where closed doors are preferred. Hydraulic or spring door-closer does the same function. In refrigerators a magnetic gasket pulls and keeps the door shut. Some refrigerators often have doors locking hinges on both sides, allowing a door to be opened on left or right side. Salon and government offices have flaps or mid door shutters, with a double flange hinge that can open it both-ways, and also has a spring-coil to bring the shutter to the closed position.

☐ Full Mortise Hinge has one leaf mortised into the door edge, and the other leaf mortised into the door jamb. This is the most commonly used hinge configuration. Hinge sizes are specified with height first and open width second.
 ☐ Half Mortise Hinge configuration is used for door jambs that do not allow mortising, e.g. a channel steel frame. One hinge leaf is fixed to the door edge, and other leaf is surface fixed over the door frame.
☐ Half Surface Hinge configuration, has one hinge leaf is fixed to the surface of the door, and the other hinge leaf is mortised into the door jamb.
☐ Structural Hinges include arrangements that link, two or more components of a structure, but allow conditional movement without letting them come apart or separate out in specific situations. The hinged condition also allows transfer of loads, stresses and transmission of energy. Such hinge like conditions occur in bridges, cranes, vehicles, dams, canal and dyke structures.
☐ Gate Hinges are also called Building access hinges, and include heavy duty hinges for fort gates, estate gates, hanger shutter hinges.
☐ Furniture or Cabinet Hinges include Concealed hinges with spring loading, controlled closures; butter fly hinges, piano hinges, etc. A butler tray and ambulance stretcher hinge (fold up the legs flat to 90E). Card Table Hinges are mortised into the edge and allow the top (shutter of card tables’ cavity) to fold onto itself. Drop Leaf Table Hinges are mounted under the surface of a table with leaves that drop down.
Spectacle Hinge Flickr image by Guy Sie
 ☐ Micro Hinges: Micro hinges are very small in size and used for jewellery boxes, wall clocks, travel suitcases, attach, bag, micro equipment and machinery cabinets. Many such hinges use ball-mortise arrangement rather than cylinder-pin system.
☐ Floating Hinges: Behave as a normal hinge but enables one of the objects to move away from the other, hence ‘float’. Actually the hinge allows for two parallel axes of rotation, one for each object joined by the hinge, and each axis can be moved relative to the position of the other. Floating hinges are used in flatbed scanners designed to scan thick objects such as books. A sheet of paper is placed on the glass, and the cover is lowered over it. The scanner glass and the paper come together very close. If a thick book is placed on the glass, an ordinary hinge would leave the cover at an angle to the glass. A floating hinge raises the hinged edge of the cover to the level of the book, so that the cover remains parallel to the glass, but raised above it. Floating hinges are also used in two-plate electric cooking grills, as they allow for even heating of both sides of a thick piece of food without crushing it. Floating hinges are used for air craft doors, Suzuki (Maruti) delivery vans, etc.

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