GB2103389A - A feed gate control mechanism - Google Patents

Abstract

The invention relates to a mechanism for controlling the rate of feed of product to the grinding rolls of a cereal milling rollermill. The mechanism comprises four coupled units as follows: 1. A sensing device 7 mounted in a feed tube of the rollermill, the function of which is to detect the presence or absence of product en route to the grinding rolls 1,2. 2. A fluid control valve 12 actuated by the sensing device 7; the function of the valve being the control of the flow of fluid to a fluid operated positioning cylinder 15. 3. The fluid operated positioning cylinder 15, the function of which is to move the piston contained therein, the piston rod end being connected to a lever arrangement 24. 4. A feed gate 6 pivotally mounted above a feed roller 4,5 and controlled at the pivot by the lever arrangement 12. Mode of operation. Stock actuates the sensing device which then operates the control valve which in turn actuates the positioning cylinder which opens the feed gate and permits stock to enter the nip of the grinding rolls. <IMAGE>

Description

SPECIFICATION A feed gate control mechanism The present invention relates to a feed gate control mechanism, which is particularly suitable for use in rollermills.

In a rollermill, material such as cereals is fed to the grinding rolls of the mill by a pair of feed rolls. The supply of feed material to the feed rolls from a feed hopper is controlled by a feed gate via a control mechanism so that the flow rate of the material passing over the feed rolls to the grinding rolls can be varied according to the quantity of feed material available in the hopper. In this way, the supply of material to the grinding rolls can be maintained evenly over the length of the rolls and a substantially constant head of material can be maintained in the feed hopper which is constantly replenished with material.

In conventional rollermills, the control mechanism of the feed gate comprises a mechanical arrangement of levers, gears and a spring tensioning arrangement. There are various disadvantages of such a mechanical arrangement including the problems that the arrangement tends to be insensitive to small variations in the quantity of feed material available and is not sufficiently quick acting when sudden variations of the quantity available occur.

Additionally, the mechanical arrangement does not always accurately repeat the same position of the control gate for identical levels of the food material in the hopper.

The object of the present invention is to provide a feed gate control mechanism which obviates or substantially mitigates the aforesaid disadvantages.

According to a first aspect of the present invention there is provided a feed gate control mechanism comprising means for sensing the quantity of a feed material available for passage through a feed gate, which sensing means are operatively linked to control means for a fluid operated positioning mechanism connected to the gate, whereby in use the position of the feed gate can be altered to vary the rate of flow of material through the gate.

Preferably, the control means comprises a fluid control valve which is adapted to be connected to a source of pressurised fluid.

Preferably also, the positioning mechanism comprises a cylinder and piston arrangement in which the position of the piston within the cylinder is controlled by the control valve, the piston being connected to the gate whereby alterations in the position of the piston vary the position of the gate.

Preferably also, the sensing means comprises a strut connected to the control valve and adapted to vary its position according to the weight of feed material acting thereon.

According to a second aspect of the present invention there is provided a rollermill comprising a pair of feed rolls adapted to be supplied with feed material from a hopper via a feed gate, a feed gate control mechanism being provided according to the first aspect of the present invention.

An example of the present invention will now be described with reference to the accompanying drawing which shows schematically a feed gate control mechanism according to the first aspect of the invention in a rollermill according to the second aspect of the invention.

Referring to the drawing, a rollermill comprises a pair of grinding rolls 1 and 2 which are fed with material to be ground from a hopper 3 via a pair of feed rolls 4 and 5. The rate of flow of the feed material passing over the feed rolls 4 and 5 to the grinding rolls 1 and 2 is controlled by a feed gate 6 which in turn is controlled by a mechanism as will now be described.

Located within the hopper 3 is a sensing means 7 for sensing the quantity of feed material available in the hopper 3 for passage through the gate 6. This means 7 comprises a strut 8 located substantially vertically within the hopper 3 and to which is rigidly connected a plurality of side arms 9. The arms 9 comprise a series of spaced plates loated in substantially horizontal planes, which plates are thereby adapted to be acted on by the weight of material within the hopper 3. The lower end 10 of the strut 8 is connected via a lever arrangement 11 to the valve member (not shown) of a fluid control valve 12. The lever arrangement 11 comprises biassing means (not shown) whereby the strut 8 is resiliently mounted within the hopper 3 so that the strut 8 can be depressed in the hopper 3 by material therein acting on the arms 9 according to the weight of the material.

The control valve 12 is connected at one side thereof via a pipeline 13 to a source of pressurised fluid 14 and to an exhaustion valve (not shown). The other side of the valve 12 is connected to a piston and cylinder arrangement 15 via a pipeline 16.

According to the vertical position of the strut 8 within the hopper 3, the valve member of the control valve 12 is moved to permit either fluid to pass along the pipeline 16 to the arrangement 15 or fluid to pass from the arrangement 15 along the pipeline 16for exhaustion.

The piston and cylinder arrangement 15 comprises a cylinder 17 in which a piston 18 can slide to define a chamber 19, 20 on each side thereof. The pipeline 16 enters the chamber 19 located on one side of the piston 18 whilst the other chamber 20 is connected to a source of pressurised fluid 21 and an exhaustion valve (not shown) via a pipeline 22. The piston 18 is attached to a spindle 23 which passes out of the cylinder 17 via the chamber 20 and which is connected to the feed gate 6 by means of a lever in the form of a leaf spring.

The feed gate 6 is adapted to move towards or away from one of the feed rolls 5 so that the gap there between can be precisely controlled. As ali the feed material which is to pass between the grinding rolls 1 and 2 must also pass through this gap then it can be seen that the size of the gap determines the flow rate of the material to the grinding rolls 1 and 2.

The lever in the form of a leaf spring forms a connection 24 between the rod 23 of the piston 18 and the feed gate 6 and is arranged so that reciprocable movements of the spindle 23 cause the gate 6 to be moved towards and away from the feed roll 5 between a position wherein the gate is in contact with the roll 5, that is a closed position, and a position where the gate 6 is the furthest possible from the roll 5 that can be achieved with the lever in the form of a leaf spring, that is a fully open position.

The lever in the form of a spring 24 is connected at one end to a boss 25 mounted on the end of the feed gate carrying spindle and at the other end to the end of the rod 23 of the piston 18. It can be seen therefore that as the rod 23 reciprocates, the lever will transmit oscillatory motion ofthe rod 23 into rotary motion at the feed gate carrying spindle, and will therefore pivot the feed gate 6 towards and away from the feed roll 5.

In use, the sensing means 7 operate to vary the setting of the control valve 12. Depression of the means 7 causing the valve 12 to open to permit pressurised fluid to pass from the source 14 along the pipeline 16 into the chamber 19 of the cylinder 17. This causes the piston 18 to slide in the cylinder 17 to increase the volume of the chamber 19 at the expense of the volume of the chamber 20, which is exhausted via the exhaustion valve. Hence, the spindle 23 is moved further out of the cylinder 17 and the leaf spring connector operates to raise the gate 6 away from the roll 5. In this way when the hopper 3 is full, the feed gate 6 is fully open. As the hopper 3 empties and the strut 8 of the sensing means 7 rises, the control valve 12 operates to prevent the passage of pressurised fluid into the pipeline 16 from the source 14.When this happens, the source 21 pressurises the chamber 20 of the cylinder 17 which causes the piston 18 to slide in the opposite direction inth cylinder 17, the fluid in the chamber 19 being exhausted via the exhaustion valve coupled to the source 14. The spindle 23 of the piston 18 is thereby retracted into the cylinder 17 and causes the leaf spring connector to operate to close the gate 6. Hence, as the feed material decreases in volume within the hopper 3 the rate of flow through the feed rolls 4 and 5 also decreases.

In order to take account of foreign bodies which may occur within the feed material in the hopper and which may not be able to pass through the gate 6 when only partially open, a manual override arrangement 26 is provided. The override 26 is connected into the pipeline 16 via a pipeline 27 downstream of the valve 12 and enables the effects of the control valve 12 to be avoided and the piston 18 to be moved to reduce the size of the chamber 20 to the minimum possible thereby fully opening the gate 6.

The control mechanism according to the invention has several advantages over prior art arrangements.

It gives smooth operation, is sensitive to variations in the head of feed material within the hopper, and is comparatively quick acting. Additionally, repeated operation of the mechanism always gives the same results for the same head of feed material which enables a substantially constant head of material to be maintained in the hopper thereby eliminating hunting.

Known actuating fluids can be used, such as oil or compressed air. However, for cereal rollermills compressed air is the more suitable fluid as it is clean, and not likely to cause contamination of the cereal if leakage should accidentally occur.

Claims (6)

1. A feed gate control mechanism in which a sensing device mounted in the feed hopper of the machine senses the amount of feed material available and which is linked to a control means for a fluid operated positioning system connected to the feed gate which is altered in its position relative to the feed roll thereby controlling the rate of flow oT produce to the grinding rolls.

2. A mechanism as claimed in claim 1 wherein the sensing device is linked to a control valve which regulates the flow of fluid to the positioning device.

3. A mechanism as claimed in claims 1 and 2 wherein the fluid connection between the control valve and the positioning device is fitted with a manual override device to enable the effects of the control valve to be avoided and the position of the piston in the positioning device to be moved to enable the feed gate to be opened to permit foreign bodies to pass from the feed hopper and between the feed gate and feed roll.

4. A mechanism as claimed in claim 3 wherein the oscillatory motion of the piston within the positioning device is converted to rotary motion of the feed gate mounting shaft and thereby of the feed gate. This motion either opening or closing the feed gate in relationship to the feed roll.

5. A mechanism as claimed in claims 1 to 4 wherein the sensing device in addition to be linked to a control valve is also linked to a means for starting and stopping the feed rolls when the feed gate is opened or closed.

6. A mechanism for controlling the feed gate of a cereal milling rollermill substantially as described with reference to the accompanying drawing.