In buildings having the kitchen below the dining room, a dumb waiter is a necessity for serving the meals, and even where a dumb waiter is not needed from kitchen to dining room, it is a great convenience to have one running from cellar to kitchen or from laundry to upper floors.
A dumb waiter consists of a car enclosed in a shaft and suspended by ropes from a pulley, or pulleys above, so that it may be raised or lowered at will by means of a hand rope. The car itself is counterbalanced by iron weights, the extra weight due to the load being counter-balanced either by friction or resisted by a lock or grip. The car is steadied in its movement up and down by means of guide posts. The wheels and pulleys over which the ropes pass are made for this especial purpose, and are sold in sets under the name of Dumb Waiter Fittings. The car and guides may be made by the carpenter, who also usually furnishes the ropes and weights.
The size and shape of the car may be varied to suit the space available and the service required. The more common size for residences is 24 inches wide, 20 inches deep and 30 inches high, with two fixed shelves.
For tenement and apartment houses the car may be made 30 inches wide and 3 feet high, with one hinged shelf, so that a barrel may be set in it if desired.
The shaft should be at least 3 inches larger both ways than the car, and should be ceiled or plastered on the inside. With the style of machine shown in Fig. 520, a flat weight should be used to prevent the untwisting of the rope. If the weight runs between double guides, as shown, no extra space is required in the shaft, and the weight is readily accessible.
For the style of dumb waiter shown in Fig. 518, a square weight is used, running in a pocket behind. or at one side of the shaft.
Dumb waiter fittings are a regular article of manufacture, and may either be bought separately or the complete apparatus, including car, ropes, runs, counter-weight, etc., all ready to erect, may be purchased, the latter being usually the more satisfactory method.
The character and detail of the fittings vary with the manufacturer and with the size and capacity of the car and speed desired.
Figs. 517 and 518 illustrate a style of dumb waiter that is very generally used in good work.
Fixed shelves are placed at the top and bottom of the shaft for receiving the wheels, and the ropes pass through these shelves.
Fig. 518 shows the position of the wheels on the top shelf.
The rope by which the car is operated is fastened to the fixed upper shelf X, at I, and is carried down to and under the wheels E E on top of the car, up through the shelf and over the* wheel A, thence to the wheels at the bottom of the shaft and up to and over the wheels B and C, and there connected with the counter-balance by a pulley, the end of the rope being fastened to the top shelf close by where it started. A safety rope is attached to the top of the car, carried up through the fixed shelf over pulley D and connected with the counter balance so that should the operating rope break through long wear, the safety rope will keep the car from falling.
Fig. 517 - New York Safely Dumb Walter.
A brake grip, Fig. 519, is attached to the under side of the shelf, so that the hand rope which elevates the car will pass through it. A cord attached to the grip passes over a small hooded pulley and down along side of the hand rope. To hold the car when loaded beyond its balance, it is only necessary to pull on the small cord, and by pulling on the hand rope the grip is released.
It will be seen that all the working connections of this elevator are made with a single rope, so arranged that no matter how much it may stretch it will always be taut, the slack being taken up by the counter-balance, so that the slightest motion of the rope will start the car
Fig. 520 shows the working mechanism of another type of dumb waiter, also very extensively used. In this style the hand rope merely turns the large wheel by friction, and hangs loose at the bottom. Attached to the axle of the large wheel is a smaller wheel, over which a rope passes, fastened at one end to the car and at the other to the counter-weight. When the hand rope is pulled at one side or the other, the wheels are revolved and the car is raised or lowered according to the direction in which the wheels revolve.
The lifting capacity of the waiter is regulated by the size of the hand wheel, which varies from 16 to 30 inches in diameter.
The car is held automatically at any point by an automatic lock in the front bearing of the main shaft so that the car is always 'Mocked" except when the rope is pulled, at the top for the hand rope and turning the pulley wheel either by a fixed shaft or by gearing, and nearly all of the larger dumb waiters are of this type. Owing to the size of the hand wheel, this type requires more space above the top of the car than the type shown in Fig. 517.
An open car is shown in the illustration, but a box car is usually furnished.
There are several patterns of dumb waiters having a large wheel
Fig. 518 - New York Safety Dumb Waiter.
Fig. 519.-Broke Grip.