GB2103107A

GB2103107A - Mounting arrangement for a grinding roll

Info

Publication number: GB2103107A
Application number: GB08139217A
Authority: GB
Inventors: Keith Albert Rhodes
Original assignee: ROBINSON AND SON PLC THOMAS
Current assignee: ROBINSON AND SON PLC THOMAS
Priority date: 1980-12-04
Filing date: 1981-12-02
Publication date: 1983-02-16

Abstract

The invention relates to a mechanism for controlling the grinding pressure between a pair of rolls 1, 2 of a cereal milling rollermill. The moveable roll 2 has bearings pivotally mounted within a frame and urged towards the fixed roll by a fluid cylinder 9 movable relative to its piston 10. The fluid pressure viz air pressure in the cylinder is regulated by means of a pressure regulator 7 situated between the cylinder and the air pressure source. Overload by tramp material at the nip 23 creates an excess build up of pressure in the air cylinder. When this and above a pre-set value, the pressure regulator permits the excess pressure to bleed away, and permits the moveable roll to move away from the fixed roll. <IMAGE>

Description

SPECIFICATION Mounting arrangement for a grinding roll We, Thomas Robinson Er Son Limited a British Company of Rochdale, Lancashire OL 1 6 5NB, do hereby declare the invention for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement.

The present invention relates to a mounting arrangement for a grinding roll. The invention relates particularly to a mounting arrangement for a grinding roll forming part of a rollermill.

Conventionally pairs of grinding rolls are mounted so that one roll is resiliently urged towards the other by mechanical spring means. In this way, the rolls can part to permit uncrushable foreign matter to pass there between when necessary. In addition, the spring means themselves are mounted on the casing of the mill by means of a pin which is provided with a weak area so that if a foreign body is too large to pass between the rolls even when the spring means are fully depressed, the pin can shear or break to permit said one roll to move further away from the other roll of the pair. This arrangement, although inconvenient as it requires the grinding roll to be remounted, prevents substantial damage from occurring to the rolls or machine by the passage of foreign matter through the mill.

The object of the present invention is to provide a mounting arrangement for a grinding roll which obviates the need for a shear pin in the mounting and which permits the roll to move a greater distance away from the other roll of a pair of rolls than was possible with the mechanical spring means of a conventional mounting.

According to a first aspect of the present invention there is provided a mounting arrangement for a grinding roll comprising an arm adapted rotatably to mount the grinding roll and to be pivotally mounted at one end thereof, a pressurised fluid spring comprising two relatively movable components defining a chamber, which chamber is adapted to be filled with a pressurised fluid and one of which components is connected to the other end of the arm, and a pressure regulator including an exhaustion valve in communication with the chamber whereby in use the fluid pressure within the chamber can be maintained at a predetermined value so that increases in the fluid pressure within the chamber cause fluid to be bled off from the chamber via the exhaustion valve permitting said one component to move and thereby the position of the grinding roll to alter.

Preferably, the two relatively movable components comprise a piston and a cylinder in which the pistons can slide relative thereto.

According to a second aspect of the present invention there is provided a rollermill comprising a pair of grinding rolls, one of which rolls is mounted by a mounting arrangement according to the first aspect of the present invention and the other of the rolls is mounted independently to said one roll to a fixed portion of the rollermill.

An example of the present invention will now be described with reference to the accompanying drawing which shows in cross-section a mounting arrangement for a grinding roll according to the present invention.

The drawing shows a pair of horizontally mounted grinding rolls 1 and 2 for use in a horizontal type rollermill. One of the rolls 1 is adapted to be mounted to a fixed portion 3 of the casing 4 of the rollermill whereas the other roll 2 is mounted at each end thereof by an arrangement according to the invention. Each arrangement comprises an arm 5 connected to an air spring 6 which is in communication with a pressure regulator 7 including an exhaustion valve (not shown).

The arm 5 is pivotally mounted at one end as at 8 to the portion 3 casing 4 of the rollermill and is connected at its other end to the air spring 6 as will be described. The shape of the arm 5 is such that it cradles and thereby rotatably mounts the grinding roll 2. The mounting of the grinding rolls 1 and 2 is such that the rolls 1 and 2 are set parallel but slight adjustments can be made to the relative positions of the rolls 1 and 2 to obtain the desired grinding results when in use. As it is important when grinding cereal products to pass uncrushable foreign bodies between the rolls 1 and 2 without damage thereto, the mounting arrangement is adapted to permit movement of the roll 2 away from the roll 1 if the pressure acting on the rolls 1 and 2 at the nip 23 there between exceeds a predetermined value.

The rolls 1 and 2 are adapted to rotate in the direction of the arrows as shown in the drawing and matter to be ground passes through the nip 23 in the direction of the arrow A. Hence, in order to permit uncrushable foreign bodies to pass between the rolls 1 and 2 the arrangement mounts the roll 2 so that it can move in the direction of the arrow B away from the roll 1 under the effect of pressure, exceeding a predetermined value at the nip 23. Once the foreign body has passed between the rolls 1 and 2, the arrangement is adapted to return the roll 2 to its previous position in proximity to the roll 1.

This is accomplished by the air spring 6 and the pressure regulator 7 of the arrangement.

The air spring 6 comprises two relatively movable components 9 and 10 in the form of a cylinder and a piston respectively. The piston 10 is relatively slidably mounted in the cylinder to define a chamber 11 which is arranged to be fluid-tight apart from means (not shown) which communicate the chamber 11 with the pressure regulator 7 by means of pipework 12. In the present example the piston 10 is adapted to remain stationary relative to the casing 4 of the rollermill and is connected by a rod 13 passing through the chamber 11 to a toggle mechanism 14, as will be described below. The cylinder 9 is slidable over the piston 10 to vary the volume of the chamber 11 and is connected to the arm 5 so that pivotal motion of the arm 5 about its pivot point 8 moves the cylinder 9 over the piston 10.

The pressure regulator 7 is adapted to be connected to a source 1 5 of pressurised fluid via pipework 1 6 so that the chamber 11 can be charged with the fluid and maintained at a predetermined fluid pressure. In the present example, the chamber 11 is adapted to be filled with pressurised air and the source 1 5 takes the form of a compressor. However, other fluids can be used, such as oil according to the suitability of the fluid to the material which the rollermill is to grind. The exhaustion valve of the pressure regulator 7 is adapted to exhaust quickly fluid from the chamber 11 in the event that the fluid pressure therein rises above the predetermined value.

The toggle mechanism 14 is provided to permit fine adjustments to be made to the position of the roll 2 to obtain parallelism with the roll 1. The construction and operation of the mechanism 14 is similar to those used in prior art rollermills and will not be described in detail herein. However, it can be seen that the mechanism 14 comprises a vertical lever adjustment 1 7 which is located between the portion 3 mounting the roll 1 and a handwheel 22 located to the exterior of the casing 4. The lower end of rod 1 7 is pivotally connected to the toggle mechanism 14 which is mounted on an eccentric shaft 1 8 the function of which is to alter the position of the toggle mechanism 14 together with the fluid spring 6, arm 5 and roll 2 via the pivot point 19, independently of the fluid spring function.A compensating spring 20 is attached at one end 21 to the toggle mechanism 14 and at the other end to the framework 4.

In use, material to be ground is passed between the rotating rolls 1 and 2 in the direction of the arrow A. If an uncrushable foreign body happens to be caught up in the material and cannot pass through the nip 23 then excess pressure is exerted on the roll 2 and thereby on the pivotally mounted arm 5. As the arm 5 is connected to the cylinder 9 of the air spring 6 pressure is also exerted on the cylinder 9 urging it to slide over the piston 10 to reduce the volume of the chamber 11.

If the pressure exerted by the foreign body exceeds the pressure of the fluid within the chamber 11 then the pressure regulator 7 operates to open the exhaustion valve so that the pressure in the chamber 11 remains constant, the cylinder 9 sliding over the piston 10 to reduce the volume of the chamber 11. In this way the arm 5 can pivot in the direction of the arrow B and permit the roll 2 to move to increase the size of the nip 23 and allow the foreign body to pass therethrough. Once the body has passed through the nip 23 and the pressure on the roll 2 has decreased, the pressure exerted on the cylinder 9 by the arm 5 will also fall. The pressure regulator 7 then acts to close the exhaustion valve and to pump fluid back into the chamber 11 to restore the pressure therein to the predetermined value.

The chamber 11 is thereby restored to its initial volume, moving the cylinder 9 and the arm 5 to their initial positions and bringing the roll 2 back to its close proximity to the roll 1.

It will be appreciated that during the passage of a foreign body between the rolls 1 and 2, the toggle mechanism 14 can still be used to effect manual adjustments to the relative positions of the rolls 1 and 2. Additionally, the provision of the compensating spring 20 ensures a speedy parting of the rolls 1 and 2 and assists in maintaining free movement of the handwheel 22 during the time when the rolls 1 and 2 are parted.

The mounting arrangement according to the invention has many advantages over conventional arrangements. Firstly, the gap which can be achieved between the rolls 1 and 2 is significantly greater than that which could previously be achieved without making use of the provision for shearing of a pin attaching the arm to the toggle mechanism. It can be seen that as a result of the fact that the arrangement is self-regulating the arrangement returns to its normal operating position after passage of a foreign body whereas as in a conventional arrangement there is considerable downtime if a sheared pin has to be replaced. Secondly, there is a constant regulating effect of the roll positions which is achieved by virtue of the pressure regulator 7. This gives fast separation of the rolls 1 and 2 when required and enables the grinding roll pressure to be set quickly to suit the type of grind required. Finally, the effect of the air springs or other similar fluid arrangement creates a resilient mounting the roll 2 giving a smoother grind and reducing vibration more than was previously possible with conventional arrangements. Such fluid springs also have the further advantage that they do not age in the same way as mechanical springs which fatigue and require replacement at regular intervals.

Claims

1. A mounting arrangement for a grinding roll wherein the mechanism for urging the movable roll in the direction of the fixed roll includes a fluid spring so arranged that if the pressure between the grinding rolls for any reason becomes excessive then the fluid contained within the fluid spring is permitted to escape thereby reducing the pressure between the grinding rolls.

2. A mounting arrangement as in claim 1 wherein the fluid spring is calibrated to ensure a known maximum load between the fixed and movable rolls.

3. A mounting arrangement as claimed in claims 1 and 2 wherein the fluid spring is fed from a fluid source wherein between the fluid source and the fluid spring is interposed a relief valve so adjusted to permit the fluid to escape from the spring when the pressure on the fluid is too great and to permit the fluid to enter the spring when the pressure on it is insufficient to permit correct grinding conditions.

4. A mounting arrangement as claimed in claims 1 to 3 wherein the arrangement will permit independent adjustment of each end of the movable roll irrespective of the functioning of the fluid spring.

5. A mounting arrangement as claimed in claims 1 to 4 wherein parallel opening and closing of the grinding rolls for milling purposes can be carried out without interfering with the functioning of the fluid spring.

6. A mounting arrangement substantially as hereinbefore described with reference to the accompanying drawing.