WO1985000032A1

WO1985000032A1 - Screw discharger

Info

Publication number: WO1985000032A1
Application number: PCT/FI1983/000046
Authority: WO
Inventors: Voitto Leevi Samuel Husso
Original assignee: Voitto Leevi Samuel Husso
Priority date: 1983-06-14
Filing date: 1983-06-14
Publication date: 1985-01-03

Abstract

A screw discharger intended for discharging powdery, granular or equivalent solid fuel from a storage silo. The screw discharger of the invention is supported at both ends by each its own bed carriage (2, 3), both of which carry their own running motor for imparting a feed motion to the bed carriage and by its mediation to the discharging screw (1).

Description

Screw discharger

The invention concerns a screw discharger.

Screw dischargers are usually employed to discharge solid material in the form of powder, pellets, briquettes or equivalent, such as for instance fuel peat, wood chips or coal from a storage silo for further transportation or for immediate use. Screw dischargers are particularly well suited for use in connection with storage silos discharging from the bottom.

The screw discharger comprises one or several discharging screws, discharging screw bed carriages with running track and operating machinery imparting to the discharging screw a cutting motion rotating about its axis, milling the ma¬ terial and displacing it in the direction of the screw's axis, and a feed motion at right angles to the axis of the screw.

Most screw dischargers usually have a discharging screw so long that the feed motion at right angles to the axis has to be transmitted to it by both ends of the screw. In screw dischargers of prior art, the running motor imparting the feed motion to the discharging screw has been placed in only one of the two bed carriages. The bed carriage without run¬ ning motor obtains the power required for its feed motion from the carriage provided with a running motor over a power transmission shaft placed within the hollow discharging screw or over another equivalent mechanical transmission system.

The mechanical transmission between the running mechanisms in the bed carriages of the discharging screw imposes special requirements both on the discharging screw and on the drive machinery of the screw discharger. Dismantling the discharg¬ ing screw for repairs and servicing is difficult in these screw discharger designs of prior art owing to the power transmission shaft placed within the discharging screw, and it is slow work and therefore also expensive. The good ser¬ viceability of the screw discharger is particularly accen¬ tuated when it is used to dispense fuel in a power plant.

Another considerable drawback of screw dischargers of prior art is the fact that it is relatively difficult in them to provide for good sealing between the storage silo and the spaces set aside for the drive machinery of the screw dis¬ charger.

The screw discharger of the invention is free of the draw¬ backs of the screw dischargers known in the art. The screw discharger of the invention is characterized in that which has been stated in the characteristic features parts of the claims following below. It may be considered the most import¬ ant advantage of the invention that the running mechanisms of the discharging screw's bed carriages have not been inter¬ connected by any mechanical transmission, with the result that the discharging screw and its drive mechanisms are simple of their design and easy to service (for instance, the dis¬ charging screw can be dismounted for servicing without dis¬ assembling the drive machinery) . The screw discharger of the invention also enables the storage silo and the drive machiner spaces to be isolated in dust-tight fashion from each other with ease. This is a remarkable safety-promoting factor in fuel storage installations.

In the following, the invention is described in detail with the aid of the attached drawing.

Fig. 1 presents a screw discharger installed in a bottom-dis¬ charging storage silo, viewed in the direction of the feed motion.

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^ Fig. 2 presents, viewed from one end of the discharging scre the right-hand bed carriage of the screw discharger of Fig.

Fig. 3 shows, viewed from the other end of the discharging screw, the left-hand bed carriage of the screw discharger depicted in Fig. 1.

The screw discharger depicted in Fig. 1, which is an advan¬ tageous embodiment of the invention, comprises a discharging screw 1, the bed carriages 2 and 3 and the running tracks 2a and 3a for the bed carriages, and the bracing rail 3. The running tracks are located above the carriages, whereby the floors are left free for passage, cleaning and maintenance.

In the right-hand carriage of the screw discharger depicted in Fig. 1, which has been more closely shown in Fig. 2, are located the drive machinery 4 of the discharging screw (moto 4a, fluid clutch 4b and gear transmission 4c) and the runnin machinery 5 for the carriage (motor 5a, gear transmission 5b, tooth rack/gear wheel traction mechanism 5c and pick-up 5d measuring the displacement of the carriage, this pick-up belonging to the control system) . On the left carriage of the screw discharger of Fig. 1, in its turn more closely dis played in Fig. 3, is located only the running machinery 6 fo the carriage (running motor 6a, gear transmission 6b, tooth rack/gear wheel traction mechanism 6c and pick-up 6d measur¬ ing the displacement of the carriage, this pick-up belonging to the control system) . The discharging screw is coupled to both bed carriages with flange junctures 7, which are easy to undo.

In Fig, 1 havefurthermore been presented supporting struc¬ tures 8 of the discharger, which actually are part of the silo building. Furthermore, in Fig, 1 is shown the belt con¬ veyor 9 onto which the screw discharger transports -material from the silo. The sealing arrangements between the silo and the spaces for the screw discharger's operating machiner havenot been depicted, but it is well obvious from Fig. 1 that the sealing is easy to accomplish. In the figure have not either been depicted the pick-ups measuring the displace¬ ments of the carriages, except for the system controlling the position of the discharging screw (the control system for the difference Λs of the carriages' feed motions) and the equip¬ ment belonging thereto, known in itself in the art.

The screw discharger of the invention operates in the same manner as the screw dischargers of prior art: the drive ma¬ chinery of the screw discharger is started and the screw is fed by means of the running machinery in accordance with the need of discharging material.

In the embodiment example of the figure, the screw discharger has been provided with an automatic control system known in itself in the field of control technology, this system taking care that the difference ^ s = Avt od the feed motion dis¬ tances, where Δvt = the difference between the velocities of the carriages, cannot increase to a magnitude impeding the feed motion (_&s = _Δ s, ) .

The control system operates in principle so that the pick-ups (angle transducers) 5d and 6d measure from the rotation of the traction gear wheels the displacements of the bed car¬ riages, on the basis of the difference of which the system governs the speeds of the running motors so that the angle of the discharging screw with reference to the running tracks is constant with sufficient accuracy (^s stays smaller than the set-point valueAs, ) . When the running motors are of the squirrel-cage rotor type, control of the running motors is rather advantageously managed by on/off control.

The screw discharger of the invention may naturally be pro¬ vided with requisite automatics and safety systems, such as extreme travel and bumping limits.

The invention has in the foregoing been described with refer¬ ence to only one advantageous embodiment example. By this it is however in no way intended to restrict the invention to concern this example only. Numerous alterations and applica¬ tions are possible within the scope of the invention fined by the claims following below.

Claims

1. A screw discharger in a store or intermediate store for material in the form of powder, pellets, briquettes or equiv¬ alent such as fuel peat, wood chips or coal, comprising at least one discharging screw (1), bed carriages (2,3) for the discharging screw with their running tracks (2a,3a) and drive machineries (4,5,6) for imparting to the discharging screw a rotary cutting motion about the axis of the discharging screw and a feed motion at right angles to the axis, characterized in that the discharging screw is supported at both ends by each its own bed carriage (2,3), these both having their own running motor (5a,6a) for imparting a feed motion to the bed carriage and by its mediation to the discharging screw (1) .

2. Screw discharger according to claim 1, characterized in that the feed velocities of the bed carriages (2,3) and there¬ by the feed velocities of the ends of the discharging screw

(1) have been controlled by a speed control system of the running motor (5a,6a) known in itself to be such relative to each other that in all positions of the discharging screw the imaginary extensions of its axis intersect at least approxi¬ mately at the same point.

3. Screw discharger according to claim 2, in which the motion paths of the bed carriages are straight and parallel, charac¬ terized in that the difference JΔs = -4vt of the feed motion travels of the bed carriages (2,3) ha* been controlled to remain smaller than the difference s, impeding the ffiefeion of the carriages.

4. Screw discharger according to claim 2 or 3, characterized in that the running motors (5a,6a) of the bed carriages (2,3) are motors with squirrel-cage rotor and the control system operates according to the on/off principle.

5. Screw discharger according to claim 1, 2, 3 or 4, charac¬ terized in that the discharging screw (1) has been attached to the bed carriages (2,3) supporting it with easy to open junctures, such as flange junctures (7) . _**^R RE

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