TRANSPORTATION,
DOSING, AND COMPACTIFICATION
NEW DESIGN OF A SPIRAL-SCREW CONVEYER V. N. Ivanets and V. G. Menkh
UDC 621.867.4:62-492
Existing designs of spiral-screw conveyers do not guarantee reliable transport of materials which flow together and are hard to break up, because during equipment downtime the material flows together and solidifies. Because the coefficients of internal and external friction of the transported material is much larger when it is not moving than when it is, the transport spiral often breaks near the drive shaft when the conveyer is started up. We developed an original technical solution to remove this deficiency [i]. The proposed conveyer (Fig. la) works as follows. A flexible tube 5 is mounted at a given angle, and a rotating spiral 3 with a flexible connecting strip 4 moves the transported material along the axis to the receiving equipment. The presence of connectors 1 with fillets 2 makes it practically impossible to prevent material motion along the flexible tube~ When the conveyer stops, the friable product is held by the spiral and the fillets. As a result, voids are formed, and all the material which fills the conveyer is divided into a series of portions which are weakly bound to each other. This makes the startup of the conveyer much easier. At the same time the use of doubled spirals of variable thickness makes possible a large increase in the strength of the most highly loaded part of the transport unit, which is connected directly to the drive shaft. In order to increase the throughput and wear resistance of spiral-screw conveyers [2], the following original technical solution is suggested (Fig. ib). The device consists of a flexible shell 5, within which is placed a spiral spring with coils placed right next to each other. The spiral is predeformed by torsion and compression, so that a worm conveyer is formed in the shape of a standing wave with circular polarization. One end of the spiral is rigidly mounted to the flange 1 of the conveyer, and the other to the rod 4, which is eccentrically mounted on a rotating disk. When the disk 6 rotates, the rod 4 starts to move back and forth in a circle. This does not twist the spiral further, and the wave that is formed starts to move and transport the material from the hopper 3 to the connector 2. The direction of the wave motion is determined by its polarization and the corresponding rotation of the disk 6.
~
y
v
~
~
~
,
x
x
~
x
x
x
xx x >Lxx~
/ / / / / i
2 5
4 5
a
b
Fig. i. Conveyer designs: a) spiral screw; b) spiral screw with an oscillating worm. Translated from Khimicheskoe i Neftyanoe Mashinostroenie, No. i, p. 25, January, 1992.
46
0009-2355/92/0102-0046512.50
9 1992 Plenum Publishing Corporation
The proposed spiral-screw conveyer has a series of advantages. First, the spiral can be made from small-diameter wire, that is, it is less rigid than in analogous conveyers. As a result, the conveyer has greater flexibility, which in our case is essentially determined by the rigidity of the shell. Moreover, the pressure of the worm drive is reduced, which reduces the friction and increases the wear resistance of the spiral material and the flexible shell. Second, a worm drive can be made from the flexible spiral, whose fillets almost completely fill the internal cross section, which increases the throughput of the conveyer. It should also be noted that it is possible to use these devices in current devices for transporting and mixing friable materials [3, 4]. LITERATURE CITED 2.
Inventor's Certificate No. 147,939, USSR, MKI B 65 G 33/16, Spiral-screw conveyer. P. A. Preobrazhenskii and A. A. Trufanova, "Spiral-screw transporters (flexible worm drives) and mixers," Collected articles, Kazan' Chemical Engineering Institute, Kazan'
(1970). .
4.
Yu. I. Makarov, "Problems of mixing friable materials," Zh. Vses. Khim. Ova., 33, No. 4, 24-29 (1988). Kh. Gerrman, Worm Drive Machines in Industry [in Russian], Khimiya, Leningrad (1975).
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