Roll mill

Abstract: Disclosed is a device for automatically adjusting the roll gap (20) between the rolls (1,2) of a roll mill including simultaneously operated screw jacks (11) which adjust the gap (20) and a shaft mounted geared box drive (9)to accomplish the drive of the secondary roll from the primary roll further including a drive tensioning device which permits automatic adjustment of the roll gap (20) while maintaining tension between the drive belts (8)utilized for driving the shaft mounted gear box. The combination permits the automatic selection and adjustment of roll gap without further adjustment to accommodate the drive to the different roll gap settings.

Description: This invention relates generally to a roll mill assembly for particle reduction including grinding and cracking of, for example, feed products. Two of the common problems associated with roll mills are the adjustment of the rolls relative to one another to effect the grinding or crushing of the particulate matter between the rolls and the drive means required for driving the two rolls simultaneously from a single power source at different speeds required for efficient particle reduction. In the past, this has been accomplished by either independent drives or cumbersome devices requiring additional adjustments with varying roll gaps. DE-A-25 19 508 and DE-A-503 661 both disclose means for allowing the gap or spacing between two rolls of a roll mill assembly to be adjusted. US-A-3 884 421 discloses a roll mill assembly with upper and lower rolls, one of the rolls being driven by means mounted on a frame. When it is desired to separate the rolls without interrupting the drive to them to adjust the nip or gap between the rolls, the drive means is actuated to swing the frame about an axis and a gear box carried by one of the roll shafts is urged to move with the frame. However, the gear box is held by a torque bar and is rotatable relative to the gear box output shaft and roller shaft, so that the gear box housing rocks about the aforementioned axis of the roll shaft to which it is mounted. It is believed that this rotation of the gear box being restrained by the torque bar is unnecessary and undesirable. According to the present invention, there is provided an adjustable roll mill assembly comprising a pair of opposed rolls in longitudinal alignment and comprising a primary roll and a dependent roll mounted in bearings permitting the adjustment of distance between the centrelines of said rolls; means for adjusting the distance between said rolls; a primary drive means for said primary roll; a drive means interposed between said rolls to accomplish drive of said dependent roll including a gear box mounted for rotation on an end shaft of one of said opposed rolls having a first drive element in axial alignment with the centreline of said one roll and a second gear box drive element in fixed parallel offset axial alignment with said first drive element; said first drive element being driven by said second drive element at a selected drive ratio; and drive means interposed between said second drive element and the other of said opposed rolls for transmitting drive between said second drive element and the other of said opposed rolls; characterised in that said drive means includes selectively adjustable means for establishing the distance between the centreline of said second drive element and said other of said opposed rolls and to prevent rotation of said gear box about said one of said opposed rolls. For a better understanding of the invention and to show how the same may be carried into effect, reference will now be made, by way of example, to the accompanying drawings, in which:- Figure 1 is a plan view of a roll mill drive and adjustment means of a roll mill assembly, Figure 2 is a front view of a stack of assembled roller pairs, Figure 3 is a side view of the stack of assembled roller pairs, Figure 4 is a partially sectioned end view of bearings for the rolls, Figure 5 is a partially sectioned end view showing a roll adjustment device in detail, Figure 6 is a plan view of a shaft mounted gear box, Figure 7 is an end view of the shaft mounted gear box, Figure 8 is a side elevation of the shaft mounted gear box, Figure 9 is an end view of a belt tensioning device in its maximum takeup position, Figure 10 is an end view of the belt tensioning device in its minimum takeup position, and Figure 11 is a front elevation of the belt tensioning device showing a belt guard mounted in place. Referring to Figure 1 an adjustable roll assembly is shown having a pair of adjacent rolls 1 and 2 having an adjustable gap 20 therebetween. The primary driven roll 1 is shown mounted in a pair of bearings 3 for rotation on a shaft 30. The driven roll 2 is likewise mounted for rotation in bearings 3' on a shaft 31. Particles passing in the gap 20 between the rolls will be ground, cracked or otherwise commuted and reduced in particle size. A main drive motor 5 rotates the driven roll 1 through a main drive V-belt drive 4. Drive of the driven roll 2 is accomplished by power takeoff from the roll 1 through an extension of its shaft 30 to a V-belt drive 8 which in turn drives a driven gear box shaft 32 and, through a gear reduction in a shaft mounted gear box 9, drives a driven roll shaft 31 and hence the driven roll 2. Details of the power takeoff drive will be more fully explained later. The driven roll is urged towards the drive roll by a pair of precision machine screw jacks 11 which jack against the bearings 3' through a set of strong disc springs 10. Positioning of the jack screws is accomplished by a motor 17 driving jack nuts through an angle drive 16 and a coupling shaft 15 having a rigid coupling 14 which permits the simultaneous adjustment of the jack nuts and hence the extension of the jacks at both ends of the roll. An optical encoder 18 and controller 19 with digital readout 21 permits accurate setting of the gap 20 by automatically adjusting the extension of the machine screw jacks. Parallel adjustment between the two jacks may be accomplished by a manually adjusted rigid coupling 14 and the minimum roll gap adjustment can be made manually by a hand wheel 13 or automatic remote control using the optical encoder and controller. The adjustment of the gap 20 may now be accomplished by automatic means. To further permit this adjustment, without further adjustment of the drive means between the rolls, a power takeoff or interroll drive is provided. Referring to Figures 6 to 8, a non-rotating tension base 6 is bolted to the bearing block of the drive roll 1. Mounted for rotation on the tension base 6 is a driving roll tension ring 33. A similar roll tension ring 34 is mounted for rotation on a gear box extension 12 on the gear box 9. The gear box 9 has its output on a gear which drives the driven roll 2 through the shaft 31. The shaft mounted gear box 9 is otherwise free to rotate about the shaft 31. The V-belt drive 8 transmits power between the drive roll shaft 30 and gear box shaft 32. The gear box in turn has its power output as previously mentioned on shaft 31. Referring to Figure 7 it should be apparent that for the roll gap 20 to change, the distance between the shaft 30 and shaft 31 will similarly change. The shaft mounted gear box 9 is restrained from rotation about shaft 31, about which it is free to rotate by a belt tensioning device which may be more readily understood by referring to Figures 9 to 11. The belt tensioning device is comprised primarily of two tension rings: a driving roll tension ring 33 and a gear box tension ring 34. Each of these tension rings are free to rotate about the respective devices on which they are mounted, i.e., the tension base 6 which is concentric about the drive roll shaft 30 and the gear box extension 12 which is concentric about the driven gear box shaft 32. A lug 22 extends from each of the tension rings 33, 34, and are joined together by a pivot 24. Also extending from the tension rings are a pair of fingers 36 which are operably joined together by means of a turnbuckle 35 attached to each of the fingers 36 by a pin 40. It should be appreciated by referring to Figures 9 and 10 that as the turnbuckle is extended the rings are rotated about the tension base and the gear box extension from a position wherein the lugs 22 are positioned near the centreline providing maximum belt tension to a position shown in Figure 10 when the turnbuckle is extended wherein minimum belt tension is provided. Also extending from the tension rings are a pair of guard attachment lugs 23. As shown in Figure 11 a guard 29 may be mounted to the tensioning device by means of a guard mounted bolt 37 and a spacer 39. The bolts co-operate with the guards 29 in a slot 38 which accommodates the required movement between the centrelines of the bolt attachment points on the guard attachment lugs 23. Tension in the V-belt drive between the drive roll shaft 30 and the driven gear box shaft 32 may be readily accomplished and maintained regardless of the orientation of the tensioning device about the tension base 6 or the gear box extension 12. Since the tensioning device is free to rotate, and the gear box is also free to rotate, it will be appreciated that although the distance between the drive roll shaft and the driven gear box shaft may remain constant, to accomplish belt tension, the dog leg formed between the tensioning device and the offset of the gear box housing provides for the required variation in the gap 20 between the rolls simply by rotation of the dog leg without further adjustment. Figures 2 and 3 show a convenient arrangement of three roll assemblies 26 stacked in a vertical arrangement being fed by a roll feeder 27. The convenience of the roll adjusting mechanism and the orientation of the roll adjusting device may now be appreciated in relationship to the main drive motors. Referring to Figure 4, the bearing mounting assembly is shown mounting the bearings 3, 3' in a U-shaped guide 28 which permits the movement of the mounting bearings towards and away from each other. Control of this movement is accomplished by a lock screw 41 in the case of the drive roll bearing 3 and by means of the machine screw jacks 11, 15' providing force against the driven roll bearing 3' through the disc springs 10. The disc springs are provided to allow for the rolls to move apart to prevent damage in case of overload created, for example, by tramp material passing between the rolls. The guides 28 are formed in a U-channel which permits the bearing blocks 3 and 3' to move in a linear direction apart and conversely together. In operation, it will be appreciated that the gap 20 may be automatically adjusted by sensing the gap by means of the optical encoder and adjusting the gap by setting the required gap in the controller 19 which in turn would control the motor which drives the machine screw jacks as previously described. The new roll gap is accomplished without further adjustment and operation may be immediately resumed or continued during operation.

Claims: An adjustable roll mill assembly comprising a pair of opposed rolls (1, 2) in longitudinal alignment and comprising a primary roll (1) and a dependent roll (2) mounted in bearings (3, 3') permitting the adjustment of distance between the centrelines of said rolls (1, 2); means (11) for adjusting the distance between said rolls (1, 2); a primary drive means (5) for said primary roll (1); a drive means interposed between said rolls (1, 2) to accomplish drive of said dependent roll (2) including a gear box (9) mounted for rotation on an end shaft (31) of one (2) of said opposed rolls (1, 2) having a first drive element (31) in axial alignment with the centreline of said one roll (2) and a second gear box drive element (32) in fixed parallel offset axial alignment with said first drive element (31); said first drive element (31) being driven by said second drive element (32) at a selected drive ratio; and drive means (8) interposed between said second drive element (32) and the other (1) of said opposed rolls (1, 2) for transmitting drive between said second drive element (32) and the other (1) of said opposed rolls (1, 2); characterised in that said drive means (8) includes selectively adjustable means (6, 33, 34) for establishing the distance between the centreline of said second drive element (32) and said other (1) of said opposed rolls (1, 2) and to prevent rotation of said gear box (9) about said one (2) of said opposed rolls (1, 2). An assembly according to claim 1, wherein said roll bearings (3, 3') are mounted in linear slide means (28). An assembly according to claim 1 or 2, wherein said means for adjusting the distance between said rolls comprises a pair of machine screw jacks (11) which are simultaneously operated. An assembly according to claim 1, 2 or 3, wherein said drive means further comprises a tension adjustment and positioning means (33-36) interconnecting said gear box and a tension base (6) mounted on a bearing (3) associated with said other opposed roll. An assembly according to claim 4, wherein said drive means comprises a V-belt drive (8) and said tensioning means provides tension and adjustable spacing between sheaves of said V-belt drive. An assembly according to any one of the preceding claims, wherein said selectively adjustable means comprises a spring tensioning device having tension rings (33, 34) mounted for rotation on one of said opposed rolls and said second drive element, said tension rings being connected by pivot means (24) and further being provided with means (35) for effecting rotation about said pivot to accomplish a change of centre between said primary roll and said second drive element. An assembly according to claim 6, wherein said means for effecting rotation about said pivot point further comprises a turnbuckle (35) and said ring means further comprises mounting means (23) for a guard (29) encircling said drive means. An assembly according to claim 6 or 7, wherein said means for adjusting said machine screws further comprises a simultaneously rotated pair of jack nuts which operate the jack screws (11) in extension and retraction.

Inventors: THOM KELSEY C JR, THOM, KELSEY C., JR.
Applicants: CALIFORNIA PELLET MILL CO, CALIFORNIA PELLET MILL COMPANY
Application year: 1991
Main classification: B02C4
IPC codes: B02C4