Post 663 –by Gautam Shah


Sequence of Doors Temple of Ramses III

A gap, portal or doorway, door-frame and the shutter, have an individual as well as combinative presence. Presence of one or many in physical, hyper-real or allegorical sense manifests the opening system.

Big Data Internet Virtual Reality Future

Door symbolism: A symbolic door is a representation of the nominal door or its important components or essential qualities. Door symbols are abstracted as well as scaled versions. Metaphors are also used to present the physical characteristics, crucial functions, essential qualities and historical associations of the doors. Doors denote a break and so the symbolic presentations are used to indicate the breach-able points or weak spots. In electrical circuit diagrams and pipe layout drawings the door symbols are used to denote a break, open-position or a switch. In communication field a door stands for connectivity with the world so a ‘gateway’ is where traffic converges and redistributes.

space vehicle assembly area

A physical door requires a real gap and a real shutter. The shutters open, close or take up many intermediate positions. Physical doors, however have abstract adornments or attachments that give a deceptive character to the door and belie their reality.

Nara Narayana panel on the eastern wall of the Vishnu temple

A nonphysical door may not have an opening to transit, though the portals distinctively mark the place of opening. A nonphysical door could be unreal or metaphoric. Communication gateways are such doors.

Technology Antenna Radio Satellite Communication


Notional doors: Over the years, in our minds, a shutter has become so strongly associated as the door that its presence or even notional indication suffices for the opening to be evident. ‘A shutter like configuration, over a barrier satisfies our expectation that there is a way out or in.’ The notional or representational doors, such as the painted doors on Egyptian tomb walls do not take one anywhere, but do satisfy the spiritual needs as an entryway to the other world. Such doors, drawn or carved are of real-functional size as well as of debased scale.

This blind door at Banteay Srei is flanked by colonettes.

A pseudo door exists with inadequate or no opening system. The door has no real gap for transit, no perceptible doorway, or there is inadequate shutter system. The prehensions for a door are at many levels including: functional, perception, size and scale. Such doors also exist without any apparent barrier system.

Invisible Gate that trigger a Door

Louvre the interior of the the door, places monuments.

A virtual door does not reveal itself physically, but otherwise it is functionally as effective. Modern industrial plants, estates and institutional campuses have ‘open’ gaps or invisible doors with control systems that activate a ‘shutter’ (a control system) when required. Few make-believe door frames or markers are placed to indicate the position and presence of such monitoring devices. Metal detectors’ door frames at airports and public spaces, colour coded markings on the floors, are examples of these.

Many invisible security gate features -Gatehouses to the Deep Water Harbour Wikipedia Image by CaribDigita

Make-believe doors are created to denote an entrance or boundary of an ethereal world. Stage side-wings become exit-entry points. An actor, to enact a departure from the realm, at a certain point on the stage, ceases to act or shows the backside of the body. Door frames standing in a wide terrain or the gate structure such as the Japanese Torii gates standing in wide stretch of water is an entrance.



Heritage Symbol Great Torii Of Miyajima Boundary

Metaphoric doors: Metaphoric doors manifest through signs and symbols. Such doors may not have a functional size, scale and other physical characteristics or functional utility of a nominal door.

Ent to mountain shrine

These allegorical forms are used to mark and enhance the essence of a door:

  •       variations in barriers (representing an overlap or a gap or aperture),
  •       a scaled or functionally sized gap,
  •       a passageway (indicating a pathway to or from somewhere),
  •       signs, symbols and graphics to mark linearity (a lead to some place),
  •       frames (to enclose a view and other sensual perceptions),
  •       miniature or micro-cosm frames around the deity.
  •     mythological associations with doors or openings such as: Janus -Roman, Re -Egyptian, Ganesha, Dwarpal or Kshetrapal (the Indian keepers of the gate or estate), Shen Tu and Yu Lei (Chinese guardians -two brothers of the passageway).

Symbolic Door Chinatown San Francisco gateway arch 2010 California Wikipedia Image by chensiyuan




By Gautam Shah  


Pressure Cookers with Inner and Outer Lid sealing


These are pressure doors or plug doors. As the pressure inside increases the shutter leaf presses itself harder on the outer or inner seams. The bulge (convex) shape of the lid adds to the surface area for greater efficiency of sealing. A well-designed plug door relies only on the strength of the wall around (forming the seams) it. Plug doors like situations also occur on high altitude flying passenger air-crafts. Due to the higher air pressure within the aircraft cabin than of the surrounding atmosphere the door seals itself. This prevents the opening of a plug door on a pressurized aircraft. However, at lower altitudes or on landing the decompression, allows a door to be opened. Rapid Transit Series buses feature front and rear plug doors.

Hatch door with Hinge mechanism


Front loading Washing Machine Hatch Door

These are doors for entry into large tanks, reservoirs, boats, submarines, car roofs, washing machines and space vehicles. These doors like openings are very small size, just circumference of a person, and are placed in a wall or roof (though at places the wall or roof definitions are irrelevant). The door or the lid is either hinged one or is a free unit. The hatches have a glass lid, glass a view window, but all in bulged form. The hatches are required to fit snugly so have air-water tight gasket lining. The door closing is secured through multiple snap-clamps or bolts. The opening and shutting are often triggered by the pressure conditions on either side of the lid. The hatches in walls are slightly raised, whereas the in floors these have a marked and raised perimeter or are fitted in level with the surrounding structure. Hatch doors are designed as less frequently used opening system, but snug-closing is important. Ship and aircraft windows which are fixed and are round edged openings are also called hatch openings. Automobiles also have a roof level hatch openings.

Space Module Hatch Door

Submarine Hatch Door


These are similar to hatched openings, but could be as large as the mouth of the reaction vessel, or of functional size that allows addition of raw materials or drawing out a batch sample. These shutters are rim over the rim fitting type or flat-edge fitting systems where no internal pressure generation occurs. Otherwise, for pressure reaction vessels, the shutter systems are similar to domestic kitchen pressure cookers.

Chemical reaction vessels


A paint tin lid is a common example of a non plug door. It relies on the wedge shape of the seam edge. Canvas sheets in artists’ frames are held by clamps.

Paint Tin Lid


Valves have a closing diaphragm or a plunger to seal an opening and thereby cut the flow. Butter fly valves have a central pivoting diaphragm similar to wings of a butterfly. Ball valves have a ball which gets displaced by the pressure of liquid or gas, but shuts the opening by falling down due to gravity, and thereby prevent any floe in reverse direction.

Butterfly Valve


Old style Camera shutters have multiple flaps, which is pin pivoted at the outer edge, whereas the inner edges overlap. The flaps open and close very simultaneously and quickly by a rotating mechanism that actuates the outer edge of the pivot. The inner edges form a polygon or nearly a circle, thus giving a smooth edge to the picture being shot. New technology cameras have CCD devices which are activated by an electrical impulse.

Camera Shutter