EP0212882A2

EP0212882A2 - Cereal flaking mill

Info

Publication number: EP0212882A2
Application number: EP86305880A
Authority: EP
Inventors: Walter E. Buske; Stanley Woodworth
Original assignee: Wolverine Corp
Current assignee: Wolverine Corp
Priority date: 1985-08-07
Filing date: 1986-07-30
Publication date: 1987-03-04
Also published as: JPH0657323B2; CN86104859A; EP0212882A3; KR870001872A; JPS6233553A

Abstract

A roll mill has a pair of rotatably mounted rolls (14, 16), together with means (30, 32, 34) for driving the rolls in opposite direction, guide means (24) for feeding material to be milled into the nip between the rolls and means beneath the rolls for collecting the milled product. Each roll includes a through shaft (160) on which a set (64, 74) of concentric sleeves are mounted with a spiral coolant flow passage (76) defined between the sleeves. The outer sleeve (74) is of hardened metal and a coolant inlet (110) at one end of the through shaft is in communication with the spiral flow path and a coolant outlet (116) at the other end of the through shaft is similarly in communication with the spiral coolant flow path. Disposed between the shaft and the set of concentric sleeves is nonmetallic expanding aggregate material (68) of lower density than that of either the shaft or the sleeves.

Description

This invention relates to mills, and more particularly to mills for production of cereal flakes from processed grains such as corn, wheat or rice, and to rolls for use in such flaking mills and the like.
In the production of cereal flakes, processed grains with additives in the form of pellets of about three-sixteenths inch dimension are passed through a flaking mill to produce flakes of about 0.015 inch thickness and a diameter of about one inch. As it is desired that the pellets be formed into flakes of uniform thickness for further processing such as toasting, and because of the hard pellets, large external forces (forces at the roll nip of over 100,000 pounds) are required to satisfactorily form the flakes and the dimensions of the nip between the flaking rolls must be controlled with precision. In addition the flaking process generates substantial quantities of heat which must be removed in order to satisfactorily produce cereal flakes of desired quality and uniformity.
In accordance with one aspect of the invention, there is provided a roll mill with opposed side frames between which are rotatably mounted a pair of rolls, together with means for driving the rolls in opposite directions, guide means for feeding material to be milled into the nip between the rolls and means beneath the rolls for collecting the milled product. Each roll includes a through shaft on which a set of concentric sleeves are mounted with a coolant flow passage defined between the sleeves. Preferrably the outer sleeve is of hardened metal and structure defining a spiral coolant flow path is disposed between the two sleeves, a coolant inlet at one end of the through shaft is in communication with the spiral flow path and a coolant outlet at the other end of the through shaft is similarly in communication with the spiral coolant flow path. Also preferrably disposed between the shaft and the set of concentric sleeves is nonmetallic material (in a particular embodiment an expanding aggregate) of lower density than that of either the shaft or the sleeves.
In a preferred embodiment, one roll is fixed in position and the other roll is supported for movement toward and away from the fixed roll to vary the dimension between the nip of the two rolls, the adjustment mechanism including a double acting hydraulic cylinder mounted on the fixed frame member and having a rod secured to the auxiliary roll support frame and carrying a transducer for sensing the position of the rod to provide precise positioning of the moveable roll relative to the fixed roll.
In a particular embodiment, each roll has a diameter of about twenty six inches and a length of about forty inches and includes a through hardened alloy steel outer sleeve (of hardness greater than 50 Rockwell C), a steel inner sleeve, and a set of internal spiral cooling passages that are bounded by the steel sleeves. Coolant is flowed under turbulent conditions (Reynolds Number above 2000) through the cooling passages. An adjustable angle doctor blade with oscilating drive is associated with each roll. The system provides a roll nip force of approximately 250,000 pounds across the forty inch long nip and the deflection of each roll is less than one half thousandth inch. The mill produces quality cereal flakes of uniform thickness and high quality from processed grain pellets.
Other features and advantages of the invention will be seen as the following description of a particular embodiment progresses, in conjunction with the drawings, in which:

Figure 1 is a perspective view of a cereal flaking mill in accordance with the invention;
Figure 2 is an end view of the flaking mill shown in Figure 1;
Figure 3 is a side view of the flaking mill shown in Figure 1;
Figure 4 is a side elevational view (partially in section) of a flaking roll employed in the flaking mill of Figure 1;
Figure 5 is a sectional view taken along the line 5-5 of Figure 4; and
Figure 6 is a sectional view (to an enlarged scale) showing aspects of the pivot and bearing support for the movable roll of the flaking mill shown in Figure 1.

DESCRIPTION OF PARTICULAR EMBODIMENT

The flaking mill shown in Figures 1-3 includes two heavy duty side frames 10,12 (seven inch thick solid hot rolled steel) between which flaking rolls 14, 16 (each about twenty- six inches in diameter and forty inches long) are mounted. Each side frame 10,12 has a base 18 that is mounted on concrete pedestal 20 by a five-sixteenths inch thick vibration pad. Grain pellets to be flaked are fed into feed chute 24 for flow into the nip of rolls 14,16 and the flaked product is discharged onto a transport conveyor disposed between pedestals 20.
Rolls 14,16 are driven by 100 horsepower AC motors 30, each of which is coupled to its corresponding roll via high torque drive belt 32 and shaft mounted speed reducer 34. The speed of each roll is monintored by toothed gear 36 and cooperating magnetic pickup. An adjustable angle doctor blade 40 associated with each roll is mounted on shaft 38 for pivoting movement as controlled by air cylinders 42, the two blades 40 being oscillated by drive 44 and cam 46 that produce an axial travel about one-eighth inch.
With reference to Figures 4 and 5, each flaking roll 14, 16 includes a steel shaft 60 that has a body section 62 of twelve inches outer diameter on which inner sleeve 64 (twenty- two inches in outer diameter and one and one quarter inches wall thickness) is secured by end plates 66 that are welded to body section 62 and to sleeve 64. The space between shaft 60 and sleeve 64 is filled with Por-rok expansion aggregate 68 that expands about 0.3 percent as it cures over an interval of two to three days and provides a rigid composite roll base of shaft 62, sleeve 64, endplates 66 and aggregate 68. Continuously welded on the outer surface of sleeve 64 are a series of four steel flats 72 (each of three-eighths inch by one half inch cross section) in a spiral with a pitch of one and one half inch and a lead of six inches. The outer surfaces of the spiral flats 72 are machined to a precision diameter of 22 7/16 inches. Outer sleeve 74 (a 4150 steel alloy forging that has an outer diameter of about 26 inches and a wall thickness of 1 25/32 inches and that is through hardened to Rockwell C58-64) is shrink fitted over the spiral flats 72 to provide an interference fit of about 0.015-0.020 inch, and to define four spiral coolant circulation channels 76 between the inner surface of hardened outer sleeve 74 and the outer surface of inner sleeve 64. A ring 78 is welded to each end of sleeve 64 and end disks 80 are welded to shaft 60 and sealed to outer sleeve 74, the sleeve-disk joints being sealed by 0-ring 82 and cap plates 84 with thermal insulation 86 disposed on ene plate 80 between each seal disk 84 and the weld 78.
Formed in each end of each shaft 60 is a coolant flow passage that includes an axial portion 90 and four radial portions 92 that extend into the radial flow region between endplates 68 and 80 with rings 78 providing flow restrictions between those regions and the inlets and outlets of the coolant flow passages 76. Formed on the outer surface of the shaft 60 on either side of body section 62 is a tapered surface 94 on which a spherical roller bearing assembly 96 (SKF-23248K) is mounted and secured by ring nut 98. Seal. plates 100, 102 carry split seals 104 and protect the bearings 96.
With reference to Figures 1, 3 and 6, coolant is flowed through inlets 110 and rotary couplings 112 to the shaft inlet passage portions 90 for flow at a rate of 10 to 100 gallons per minute to produce turbulent flow within flow passages 76 for cooling the rolls 14, 16, and then discharge at the opposite end of the shafts 60 through couplings 114 and conduits 116.
The bearing assemblies 96 for roll 16 are mounted in auxiliary frame members 120 that are of the same thickness as side frames 10 and 12. Welded to each auxiliary frame 120 are two two inch thick side gussets 122, 124 that extend downwardly on either side of the main frame members 10, 12 and are supported on pivot shafts 126 that are press fitted into side frames 10, 12 respectively to define a pivot axis about seventeen inches below the axis of roll 16. Pivot shafts 126 are hollow and the doctor blade shaft 38 passes through those pivot shafts 126. Secured at the upper end of auxiliary frame 120 by clamp member 128 is transverse pivot shaft 130 (located about twenty inches above the axis of roll 16 - thus providing a slightly greater than 2:1 mechanical advantage). Disposed in bracket portion 132 at the top of the side frame members 10, 12 (as may be seen with reference to Figure 1) is an electrohydraulic servo actuator unit 134 (Aeroquip LESAI) that is mounted for pivoting movement about the axis of pivot shaft 126. Each actuator 134 includes a servo cylinder which has a bore of seven inches diameter and in which is disposed a double acting piston with a five inch stroke. A sonic probe in each hydrdaulic cylinder unit 134 monitors the position of the piston and provides position resolution and repeatability within 0.0001 inch. The piston rod 138 extends into a bore 142 in auxiliary frame 120 and is threaded into transverse shaft 130 to couple auxiliary frame 120 to actuator cylinder unit 134. The two cylinder units 134 are individually controllable to allow non-parallel disposition of roll 16 to compensate as necessary for unequal product feed conditions. The specific roll gap is selected by an operator adjustable thumb wheel switch and the operator may move the rolls together or apart with a jogging function. Whenever this system is shut down, servo cylinders 134 move roll 16 to a position of maximum separation and upon the system being repowered, roll 16 is moved to its original position as specified by the servo cylinder controllers.
While a particular embodiment of the invention has been shown and described, various modifications thereof will be apparent to those skilled in the art, and therefore it is not intended that the invention be limited to the disclosed embodiment or to details thereof, and departures may be made therefrom within the spirit and scope of the invention.

Claims

1. A flaking mill comprising first and second flaking rolls, each said roll comprising a through shaft, concentric inner and outer sleeve structures fixed on said through shaft, the outer surface of said outer sleeve structure defining a milling surface concentric with the axis of said through shaft, and structure disposed between and in contact with both of said concentric sleeves defining a spiral coolant flow passage,

frame structure for supporting said flaking rolls for rotation about parallel axes to define a nip through which material to be flaked is passed,

means for driving said rolls in rotation, and

means for flowing coolant through said coolant flow passages of said rolls to cool the milling surfaces of said rolls.

2. The mill as claimed in claim 1 wherein each said outer sleeve is through hardened to a hardness of at least 50 Rockwell C.

3. The mill as claimed in either claim 1 or 2 wherein the cross sectional area of said coolant flow passage between said concentric sleeves of each said roll is about ten square centimeters, and said outer sleeve structure is a solid metal shell that has a thickness of about three centimeters and a diameter of about one half meter.

4. The mill of any preceding claim wherein said means for flowing coolant through said rolls flows coolant through said coolant flow passages under turbulent conditions (Reynolds Number above 2000) .

5. The mill as claimed in any preceding claim wherein each said roll is of composite rigid structure and includes nonmetallic material filling the region between said through shaft and said inner sleeve, said nonmetallic material having a lower density than the metal of either of said concentric sleeves.

6. The mill as claimed in claim 5 wherein the cross sectional area of said nonmetallic material is greater than the cross sectional area of either said shaft or said outer sleeve.

7. The mill as claimed in any preceding claim wherein said structure defining a coolant flow passage between said concentric sleeves of each said roll includes a plurality of spiral metal members that are welded to the outer surface of said inner sleeve and said outer sleeve is shrink fitted on said spiral metal members so that a plurality of spiral coolant flow passages are defined by said spiral metal members between said inner and outer sleeves.

8. The mill as claimed in any preceding claim wherein said frame structure includes first frame structures for mounting one roll in fixed position and second frame structures for mounting the other roll for movement about a pivot axis parallel to the axes of rotation of said rolls to vary the dimension of the nip between said rolls, the pivot axis of said second frame structures being located radially outwardly of and below said other roll, and independently controllable hydraulic systems for moving said second frame structures to adjust the nip dimension of said rolls.

9. The mill of claim 8 wherein said hydraulic systems apply a force in excess of three thousand pounds per linear inch to the nip of the rolls of said mill.

10. The mill of either claim 8 or 9 wherein each said hydraulic system includes a double acting hydraulic cylinder mounted on said first frame structure that has a piston rod secured to said second frame structure and a transducer connected in feedback relation to said hydraulic cylinder for sensing the position of said rod to provide precise positioning of the movable roll relative to the fixed roll.

11. The mill of any of claims 8 - 10 and further including doctor blade structure for cleaning each said roll, the doctor blade structure associated with said other roll being mounted for pivoting movement about the pivot axis of said second frame structures.