Conveyors: power-driven – Conveyor section – Endless conveyor
Patent
1985-12-02
1987-12-29
Marbert, James B.
Conveyors: power-driven
Conveyor section
Endless conveyor
192 0094, F16D 6706, B60K 4128
Patent
active
047154918
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to high-inertia load drives, for example, for driving long conveyor belts for conveying minerals such as coal.
Conveyor belts of the type used for mining and quarrying operations may be up to many kilometers in length over 21/2 m in width. As such the belt itself represents a considerable financial investment and must be protected by appropriate controls on the machinery used to drive the conveyor belt. It is well known to use fluid couplings between a prime mover such as, for example, an electric motor and the conveyor belt drive itself, the fluid coupling being used to give a soft start and for its inherent ability to insulate the belt from shock loadings produced by the prime mover. One known control system is described by Lloyd in U.S. Pat. No. 4,223,775 where essentially a memory device stores and continuously updates the level of motor demand power from which data the application of conveyor braking on shut-down and release of brakes on start-up may be controlled. A problem with this is that the system is not capable of allowing for variation in conveyor loading during operation. Thus if the control is programmed for accelerating a loaded conveyor then a lightly loaded or empty conveyor will be accelerated much more rapidly. A consequence of this may be that in some conveyor geometries there is a risk of the material on the conveyor being spilled or of the belt being lifted off the idlers at transitions between horizontal and upwardly inclined conveyor sections. Similarly, there may be a requirement in some installations where it is necessary to limit the acceleration of a downwardly inclined and loaded belt during start-up and apply controlled braking perhaps, for example, to prevent over-speeding of the belt and bunching at changes of belt gradient. It may also be the case that in complex installations where individual conveyors discharge material on to and receive material from other conveyors it is necessary to start or stop all the conveyors in the same time period regardless of individual load and other parameters. In this way the loss of production time usually associated with running-off conveyor loads in sequence prior to shut-doown and running the material back on to each conveyor belt again on start-up may be avoided.
The control described by Lloyd in U.S. Pat. No. 4,223,775 is not able to accomplish the above requirements in that it cannot control the case where a conveyor is attempting to accelerate on a downwardly directed incline under gravity. It also cannot stop or start multiple variably loaded conveyors within the same time period, since there is no closed loop feedback of conveyor speed during these phases.
It is an object of the present invention to provide a drive and control system for a conveyor system which is able to accelerate a conveyor to a required speed within a predetermined time period or to brake it to rest within a predetermined, perhaps different, time period regardless of load. It is another object to provide drive and control systems for multiple conveyors which are able to start up or stop within a desired time period regardless of conveyor loading.
According to the present invention, there is provided a drive and control system for driving a high-inertia load from a prime mover, comprising a brake for holding the load stationary, reaction sensing means for indicating the reaction exerted by the brake on the load, a variable filling fluid coupling having its input connected to the prime mover and its output connected to the brake and load, the coupling having filling control means responsive to external control signals for starting and stopping the load, the filling control means being responsive to the brake reaction sensor and to the speed of the load in such a manner as, on receipt of a start-up signal, to release the brake under control such as to maintain a desired acceleration rate, and to start filling the fluid coupling such that the effect of such filling lags behind the restraining torque of the brake if the load is acting
REFERENCES:
patent: 4223775 (1980-09-01), Lloyd
patent: 4568611 (1979-09-01), Woyton et al.
AE PLC
Hinds William R.
Marbert James B.
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