The present invention relates to a rotary pipe and fixed channel auger with intermediate outer supporting elements.
As is known there are at present used several industrial open conveying systems of the belt, roller, bucket, truck, chain type, which are affected by noise and difficult maintenance problems, in addition to having a comparatively high installation cost.
Comparatively noiseless conveying systems, which do not cause any alterations of the materials, are the so-called closed systems, including the augers, or Archimedean screws, including a helical surface which turns inside a pipe which may be integral therewith or be separated therefrom.
They are conventionally used in several systems for conveying solid materials, either in a granular or liquid condition, or for mixing different materials.
Also known is an auger sorter, in which the auger is fixed and has a vertical axis.
In this device, the auger operates as a slightly slanted fixed channel, for discharging at a low speed loose materials and the like.
The conveying augers usually comprise two different types of assemblies: the first includes the spiral which is separated from the perimetrical pipe and is called, perhaps not properly, auger; the second has its full or partial spiral affixed within the rotary pipe and is usually called "rotary tube".
The industrial type of auger is mainly used for horizontal conveyance.
Rarely it is also used for conveying materials on slight slopes, these materials consisting of loose solid materials or dense liquids. For conveying granular solid materials there are conventionally used vertical augers.
The conveying device is loaded at any set region of the path, and it is likewise unloaded, by opening the bottom of the channel. The drive is provided by a longitudinal central shaft, of hollow construction, usually made of steel and supported by supporting elements spaced from one another by 2.5-3.5 m.
Several types of spirals are used and, more specifically, an iron sheet spiral, a ribbon or belt spiral, a blade spiral including a plurality of blades operating as the blade elements of a propeller, and allowing the advancing speed of the material to be changed by changing the angles of the blades, as well as a fixed-spiral auger made of a manganese steel alloy for conveying materials having high abrading properties.
Only by using comparatively great diameter shafts it has been possible to make great length of augers, having a length of up to 50 m; the diameter of the shaft being increased from 140 to 300 mm and that of the outer channel from 400 to 630 mm, the supporting elements being spaced by 7-8 up to a maximum of 10 m and, for greater spacings, several series arranged augers must be provided.
These prior auger devices, however, are affected by great problems: in fact, the volumetric mass of material which can be conveyed, that is the conveying capability of the auger is greatly reduced, the power required for driving the auger increasing proportionately to the resistances to the movements and, simultaneously, the device has a poor reliability and requires frequently maintenance operations.
Independently from its size, the spiral is interrupted at each supporting elements, with consequent great difficulties from the conveyance standpoint, and with the possibility of jams, as powder or paste materials are conveyed.
Moreover, the intermediate supporting elements are subjected to a high corrosion and, because of friction, the temperature can excessively increase so as to cause fires or explosions, whereas some types of chemical products tend to cure under high temperatures, so as to cause the above mentioned jams.
In order to reduce the maintenance difficulties, prior auger devices include a half-cut bearing element, which can be opened in order to access the support member without disassembling the auger and, usually, several augers are series arranged with consequent greater costs for the motors, electric controls and so on.