Solid material comminution or disintegration – Apparatus – With automatic control
Patent
1994-03-18
1995-07-18
Husar, John
Solid material comminution or disintegration
Apparatus
With automatic control
241227, B02C 428
Patent
active
054333911
DESCRIPTION:
BRIEF SUMMARY
This invention concerns cereal milling machines. Such machines provide a pair of grinding rolls arranged in close parallel proximity to form a nip therebetween through which stock to be milled is passed. The stock is fed to the grinding rolls at a controlled and substantially constant rate usually by a pair of feed rolls interacting with a feed gate at the bottom of a stock reservoir. The reservoir receives stock to be milled at a substantially constant rate although, in practice, this rate can vary considerably during a production run so that the reservoir becomes overfilled or alternatively empties out providing no stock to be fed to the interface of the grinding rolls.
The reservoir is usually in the form of a container mounted on the top of a milling machine and made from a transparent material so that the operator may watch the stock available for the machine.
Several kinds of sensor have been adopted for detecting the instantaneous level of stock within the reservoir. These include optical devices such as a photo-electric cell on one side of the transparent reservoir, and a light source on the other. However, these devices suffer from the disadvantage that the dust which inevitably accumulates on the internal wall surface of the reservoir, causes inaccurate sensing of the stock. Other devices include mechanical and electrical probes situated within the reservoir and providing actuation, by movement or by electrical signal, of other devices adapted to control the rate of feed through the feed gate to the grinding rolls. Such devices have suffered from the disadvantage that they interfere with the movement of stock within the reservoir, in some instances causing bridging of the stock or the creation of voids therein, and inaccurate sensing, whilst the sensors themselves are prone to failure due to the presence of the stock flowing past them. Furthermore, electrical devices such as capacitive analogue probes have been found to be susceptible to moisture and other properties of the stock with the result that the sensitivity of such level sensors has been difficult to control.
While it is required to prevent stock level in the reservoir from increasing or reducing excessively it is nevertheless important to ensure minimal changes in feed roll speed commensurate with maintaining the level of stock within an acceptable range. Hence it is important to prevent the control mechanism for the feed roll drive from altering the speed of drive too rapidly and to an excessive extent as a result of small changes in the level of stock within the reservoir. For example, if the level should rise by just a small amount then the speed of operation of the feed rolls should either remain constant or be increased only slightly, while larger and more sudden changes of level should be compensated for by appropriate acceleration or deceleration accordingly of the feed roll motor.
An object of the present invention is to provide a cereal milling machine having a stock level sensing means with consequent control of the feed of stock, wherein the aforementioned disadvantages are avoided.
According to the present invention, there is provided a cereal milling machine having a stock reservoir for incoming stock to be milled, at least one driven feed roll for metering the stock at a controlled rate from the reservoir, a variable speed motor to drive the feed roll or rolls, and a pair of grinding rolls for receiving the stock from the feed roll or rolls; characterised by a stock level control system comprising a sensor located so as to be out of contact with the stock and of a kind which does not transmit light from side to the other of the stock reservoir, said sensor being adapted to produce an electrical signal proportional to a rise or fall in stock level in the reservoir, and by control means connected to the sensor and to the motor and responsive in normal operation of the machine to the electrical signals from the sensor so as to accelerate or decelerate the feed roll motor at a rate dependent upon the degree of change in the le
REFERENCES:
patent: 3468488 (1994-09-01), Karrer et al.
patent: 4037712 (1977-07-01), Wochnowski
patent: 4856716 (1989-08-01), Burstedt
patent: 4869434 (1989-09-01), Folsberg
patent: 5174511 (1992-12-01), Ruegger et al.
Chadwick Alan M.
Jagger John C. G.
Husar John
Satake UK Limited
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