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Dumbwaiters are small freight elevators intended to carry objects rather than people. Dumbwaiters are found within modern structures, including both commercial, public and private buildings, are often connected between multiple floors. When they are installed in restaurants, schools, hospitals, libraries, retirement homes or in private homes, the dumbwaiter generally terminate in a kitchen.
A mechanical dumbwaiter was invented by George W. Cannon, a New York inventor. Cannon first filed for the patent of a brake system (US Patent no. 260776) that could be used for a dumbwaiter on January 6, 1883. Cannon later filed for the patent on the mechanical dumbwaiter (US Patent No. 361268) on February 17, 1887. Cannon reportedly generated a vast amount of royalties from the dumbwaiter patents until his death in 1897.
One of the first non-mechanical dumbwaiters in the world was used by Thomas Jefferson in his mountain home at Monticello, Virginia. He use it to limit the number of servants around the table to one, so that his guests could enjoy more of the view.
A simple dumbwaiter is a movable frame in a shaft, dropped by a rope on a pulley, guided by rails; most dumbwaiters have a shaft, cart, and capacity smaller than those of passenger elevators, usually 45 to 450 kg (100 to 1000 lbs.). Before electric motors were added in the 1920s, dumbwaiters were controlled manually by ropes on pulleys.
Early 20th-century codes sometimes required fireproof dumbwaiter walls and self-closing fireproof doors and mention features such as buttons to control movement between floors and locks on doors preventing them from opening unless the cart is stopped at that floor.
Most dumbwaiter has external fixtures which contains floor destination buttons, floor position indicator, and built-in interphone or normal telephone. When a person is using the dumbwaiter, he/she opens the doors manually, load the goods, and closed the doors again before operating the dumbwaiter. After that, he/she pushed the floor buttons to send the dumbwaiter to the desired floor. Sometimes, the person may also using the interphone or telephone to contact other person on the other floors.
Type of dumbwaiter
Dumbwaiters typically have two type of landings; Floor Type and Window Type.
Floor type dumbwaiter is installed on the same horizontal level with the floor of the passage way to facilitate carriage of goods normally carried on handcarts. This type of dumbwaiter is normally found in hotels, libraries, or corridor areas. Normally used to carry large goods such as tables.
Window type dumbwaiter is installed at the height of a man's waist, so that users can conveniently use the dumbwaiter. This type is commonly found in libraries, offices, restaurants, kitchens, and other places. It is normally used to carry books, documents, kitchen utensils, food and beverages, and other goods.
This type of dumbwaiter has a large cab with an external manual gate and it is similar to a normal freight elevator, but there are no buttons inside the car. Some large dumbwaiters may have an interior light. Passengers are usually not allowed to enter or ride it for safety reason. Button panel is located on the outside, often has a digital floor indicator.
Concept: Destination dispatch • Elevator algorithm • Elevator control system • Elevator machine room • Elevator maintenance • Elevator major alterations • Elevator modernization • Machine room less elevator
Elevator systems, controllers and equipments: Elevator fixtures • Elevator keys • Elevator special modes • Elevator doors • Door cam • Door interlocks (Interlock wiring communication system) • Door restrictor • Elevator Inspection Certificate • Emergency stop button • Floor designators • Gate switch • Old Deadman controls • Overspeed governor • Motor-generator set & Silicon-controlled rectifier (for DC-powered elevators) • Insulated-gate bipolar transistor (for AC-VVVF-powered elevators) • Regenerative converter (for AC-VVVF-powered elevators)
See also: List of elevator fixtures guide • List of elevator and escalator companies • Elevator door sill guide (Generic elevator component door sill guide) • Floor numbering (Unlucky floor numbers) • Elevator incidents and accidents