US3509815A - Roll gap control - Google Patents

Description

y 5, 1970 A. M. LLOYD 3,509,815

ROLL GAP CONTROL Filed Aug. 28, 1967 ROLLS SAME L ROLLS Y. n van-b r *om cys United States Patent 3,509,815 ROLL GAP CONTROL Anthony Michael Lloyd, Walkington, near Beverley, England, assignor to Rose, Downs & Thompson Limited, Kingston-upon-Hull, Yorkshire, England Filed Aug. 28, 1967, Ser. No. 663,631 Claims priority, application Great Britain, Aug. 31, 1966, 38,873/ 66 Int. Cl. B30b /14 6 Claims ABSTRACT OF THE DISCLOSURE A control mechanism for maintaining a constant roll gap between rolls for treating vegetable materials. The mechanism provides non-contact sensing means located adjacent the roll gap and responsive to changes in the distances between the sensing means and the barrels of the two adjacent rolls. The sensing means controls a mechanism for adjusting the roll gap, so as to maintain that gap at a constant value. The sensing means are preferably pneumatic, air jets being directed towards the two roll barrels and the back pressure being dependent on the proximity of the barrels from the sensing means.

This invention relates to rolls. The invention is particularly applicable to flaking rolls for operating on organic material where it is necessary to control the gap between the rolls to a tight tolerance and where the actual roll gap is small.

In conventional roll gap control arrangements the sensing means are normally displaced from the roll barrels themselves and measure some other parameter such as the distance between the chocks or the roll necks, for force exerted on the rolls, or the state of the outgoing material. While these other parameters will to some degree be a function of the roll gap and allow some control, they will not be an accurate measure of the roll gap or take into account all the factors on which the gap is dependent.

Accordingly the present invention provides a pair of rolls having adjustment means for adjusting the roll gap therebetween, sensing means arranged to detect a change in the distance between the sensing means and the roll barrels, and control means responsive to the sensing means to control the adjustment means to maintain the roll gap at a preset value.

Preferably, a separate adjustment means, sensing means and control means is associated with each end of the rolls.

In one form the adjustment means are wedges arranged between the chocks of the rolls, the chocks being prestressed against the wedges.

Preferably the sensing means comprise jets of air from nozzles placed in close proximity to the roll barrel surfaces so that a variation in gap between the roll barrels produces a variation in gap between the roll barrels and the nozzles and hence a variation in the back pressure in the airline. This change in back pressure may be used both to centralise the air nozzles assembly and to control the adjustment means.

By directly sensing the change in position of the surface of the roll barrels, inaccuracies arising in previously proposed control systems are reduced. The system according to the invention will thus automatically correct for alterations in roll gap due to roll expansion and contraction with temperature, non-uniform flow of feed across the length of the rolls, and uneven wear of rolls across the length of the rolls.

One embodiment of roll gap control system, in ac- 3,509,815 Patented May 5, 1970 ice cordance with the invention, will now be described, by way of example only, with reference to the accompanying diagrammatic drawing.

In the drawing a pair of co-operating flaking rolls 12, have roll barrel surfaces 13, and roll necks 14 rotatably supported in bearings 15 in bearing chocks 16. Drive means for rotating the rolls in the direction of the arrows are not shown. One bearing chock engages one end 17 of a housing while the other bearing chocks engages a piston 18 slidable in a cylinder 19 mounted in the other end 20 of the housing. Pressurised hydraulic fluid is supplied from a pump 21 to the cylinder to prestress the chocks against a roll gap adjusting device 22 comprising a pair of oppositely sloping wedge members 23, 24, the wedge surfaces of which engage corresponding wedge surfaces on the chocks, the wedge members being mounted on oppositely threaded portions of a screw 25 rotatable by a hydraulic motor 26 driven through a hydraulic control valve 27 by the pump 21.

For convenience the roll barrels are shown twice in the drawing but it should be realised that they are in fact the same rolls.

A sensing device in the form of an air nozzle assembly 28 supplied with air on line 29 is mounted so that its two air nozzles 30 are adjacent the surfaces of the two roll barrels respectively at the ends thereof, the axes of the nozzles making an obtuse angle with one another so that they are substantially aligned with two coplanar symmetrical radii of said roll barrels. The nozzles are mounted on a self centering control valve 31 so that the back pressure from the nozzles maintains the assembly equidistant from the rolls, and thus the pressure in the two nozzles the same. The nozzles are thus symmetrical about the plane through the roll gap and normal to the plane containing the axes of the rolls. The nozzles are also connected on line 32 to a diaphragm 33 which is in turn connected to the hydraulic control valve 27. In operation any change in the back pressure in the nozzles acts through the diaphragm and hydraulic control valve to adjust the wedge position to restore the roll gap X to its preset value. The assembly 28 may be adjustably mounted on a screw or the like for movement towards or away from the rolls for initially setting the roll gap.

It should be understood that an exactly similar but intillependent system is provided at the other ends of the TO S.

Capacitance or other types of proximity transducers could be used in place of the pneumatic system, and other types of roll gap adjustment could equally well be used, for example by controlling the prestressing load.

While the system is particularly useful for flaking rolls operating on organic material, it can also be used on similar applications for non-organic materials or where the magnitude of the roll gap and the tolerance on the roll gap are large.

What is claimed is:

1. The combination of a pair of co-acting rolls for treating vegetable materials and having adjustment means for adjusting the roll gap between said rolls,

non-contact sensing means arranged adjacent said roll gap to continuously detect changes in the distances between said sensing means and the barrels of said rolls, and control means controlled by said sensing means and controlling said adjustment means to maintain said roll gap at a preset value.

2. The combination according to claim 1 in which said adjustment means and said sensing means are arranged at one end of the roll barrels and which additionally comprises further and similar adjustment means and sensing means arranged at the other end of said roll barrels and further control means similarly controlled by said further sensing means and controlling said further adjustment means.

3. The combination according to claim 1 in which said adjustment means comprise Wedges located between checks for said rolls and means for urging said chocks into engagement with said wedges.

4. The combination according to claim 1 in which said sensing means is pneumatic and comprises a pair of nozzles at an angle to one another and directed respectively at the adjacent said roll barrels, a change in said roll gap producing a change in the dynamic back pressure and said control means being responsive to said pressure.

5. The combination according to claim 4 in which said control means includes a pressure sensitive diaphragm connected to said pneumatic sensing means to be responsive to said back pressure, and controlling said adjustment means.

6. The combination according to claim 1 in which said sensing means is adjustably mounted so that it will automatically maintain itself equidistant from the two roll barrels.

References Cited UNITED STATES PATENTS 895,005 8/1908 Delbert -168 X 1,365,521 1/1921 McNeil 100168 X 2,025,562 12/1935 Balsiger 100-169 X 2,051,434 8/1936 Cavagnaro 100-168 2,075,574 3/1937 Dahlstrom 72-2l 2,344,274 3/1944 Stacom 100-47 2,455,285 11/ 1948 Versaw.

2,424,856 7/1947 Schmuck 100169 X 3,186,200 6/ 1965 Maxwell. 3,358,485 12/1967 De Caro et al. 72-21 WALTER A. SCHEEL, Primary Examiner L. G. MACHLIN, Assistant Examiner US. Cl. X.R. 24137

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