Dumbwaiter

A restaurant dumbwaiter.

Dumbwaiters are small freight elevators that are not intended to carry people or live animals. In private homes today, they often connect two floors, usually with one end in a kitchen. Although building codes have regulated dumbwaiters in parts of North America since the 19th century, other dumbwaiters are not covered by regulation: in practice there are a wide variety of implementations and usages. Dumbwaiters typically have a small shaft, car and capacity compared to passenger elevators. The simplest dumbwaiters are open frames moved manually by a rope on a pulley, while sophisticated modern dumbwaiters may use the motors, automatic control systems and custom freight containers of other elevators. Dumbwaiter doors often slide upward when opening (as does dumbwaiter in photograph) for fast access.

Dumbwaiters, for example those used in homes or restaurants, may have very limited capacity; one in Thomas Jefferson’s house was barely large enough to carry bottles from the wine cellar. Recent book lifts in libraries, or mail or other freight transports in an office tower, may be larger, supporting 1000 lb loads. Modern dumbwaiters in most US and Canadian jurisdictions must comply with ASME codes, and therefore have similar features to passenger carrying elevators. (ASME A17.1 covers safety for new elevators, A17.2 elevator inspection, A17.3 safety for existing elevators, and A17.4 emergency procedures. )

Design and operation

A simple dumbwaiter is a movable frame in a shaft, suspended by a rope on a pulley, guided by rails. 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 car is stopped at that floor. Electric motors were not added until the 1920s, before which the car of a dumbwaiter was moved by manual power—hauling on the rope.

A legal complaint about a Manhattan Island restaurant’s dumbwaiter in 1915 describes operation and limitations:

"[There is]...great play between the car of the dumb-waiter and the guides on which it runs, with the result that the running of the car is accompanied by a loud noise. The rope which operates the car of the dumb-waiter runs in a wheel with a very shallow groove, so that the rope is liable to and does at times slip off...The car has no shock absorbers at the top, so that when it strikes the top of the shaft or wheel there is a loud report...the ropes of the dumb-waiter strike such walls at frequent intervals with a loud report...the dumb-waiter is often negligently operated, by running it faster than necessary, and by letting it go down with a sudden fall."

The complaint mentions that food orders are shouted up and down the shaft.

In popular culture

In a simple rope-operated dumbwaiter it is possible for human riders to hoist themselves between floors from within the car. In fiction, dumbwaiters allow characters to move unnoticed between floors. For example, in the Doctor Who story The Talons Of Weng-Chiang the heroes escape by hauling themselves in a dumbwaiter servicing a laundry. In the first Tomb Raider film, Lara Croft escapes through a dumbwaiter shaft.