While a truck with a leak-proof covered body eliminated many of the sanitary issues of garbage collection, loading these trucks was usually backbreaking work. That's because the containers had to be lifted to around shoulder level in order to be emptied into the truck. A solution to this problem was to introduce a hopper that could be loaded at waist level, and then an automatic mechanism would transfer to load into the truck. This has already been illustrated by the external hopper trucks. Unfortunately these trucks at the beginning had no way of evenly distributing the load within the body, as it entered the top. Another mechanism was necessary to evenly distribute the load, and this was pioneered by the Germans at about the same time the first external hopper trucks were introduced in the late 20s..
The key to load distribution was an auger or corkscrew mechanism (what would rotate much like a cement mixer). This would remove the material from a fixed rear hopper and then distribute it evenly within the body of the truck, moving it towards the front. The oriignal application of such a truck was ash removal, as many people had stoves to heat their homes, and ash removal was a common service. But certainly the concept was effective at handling household garbage.
Early German Designs This ash removal truck used in Potsdam (a suburb of Berlin) was built by Keller & Knappich of Augsburg, Germany. The diagram illustrates how containers are tipped and emptied into the hopper, as well as the corkscrew or auger mechnism used to move the material towards the front of the truck. Lifting the hatch at the back and runing the auger in reverse would empty the truck. The body would not have to tip up to dump the load.
It turns out a modern garbage truck (seen in Japan) has been built using this concept.
The diagram of this truck (built by Krupp Co. of Essen, Germany) shows how the auger mechnaism lifts the material out of the rear hoper and move it up towards the top front. The refuse would build up from the rear to the front in this manner. This truck required a tip to empty its load, unlike the K&K truck on the left.
Becuase it was introduced in Europe, there are still models in use over there that use this concept. In more modern trucks, the corkscrew mechanism is heavy duty, able to break down bulky objects such as furniture and TV sets, and better able to compress the load as it is augered towards the front of the truck. However they are best suited for organic waste, as their continuously rotating mechanism keeps the load homogenized like a cement mixer. Rotary trucks as such were not successful in America, the other technologies were more suitable in handling its waste management problem.
Perhaps the closest thing in use in America was introduced by Garwood in 1938. This truck also featured the fixed hopper at the rear where trash was loaded. It was emptied by an internal coveyor system that distributed the load towards the front of the truck. The fixed hopper concept, though introduced first by the Germans with their rotary loaders, was critical for the design of the revolutionary rear loader, the Load-Packer also introduced by Garwood.
This large truck was manufactured by Garwood Industries of Detroit. Garwood delivered a fleet of these trucks to New York City in the late 30s.
A chain-driven elevator lifted the refuse from the rear hopper up into the body. A second chain-driven mechanism would spread the material evenly within the body.
To empty the load, the rear hatch lifted up (along with the hopper) and the body tipped up. This principle was carried forward to other rear loader designs.
A door on the side was used for items too large to fit in the rear hopper.
Later the City Tank Corp, built a similar truck called the Roto-Pak in the early 1950. The extra feature here was an internal rotary compacting blade located at the top of the elevator that would serve to mangle and compact the load towards the front of the truck. Here we have a full page ad in the Nov. 1955 issue of The American City, featuring the major cities where it was used.
German Trucks from
from "The Commercial Car Journal and Operation & Maintenance", Oct
Garwood model from Garwood Sales News, No. 2, 1940