WO2001003841A1

WO2001003841A1 - System and self-moving device for the control of milling processes

Info

Publication number: WO2001003841A1
Application number: PCT/IT1999/000210
Authority: WO
Inventors: Alberto Bonelli
Original assignee: Imeco Automazioni S.R.L.
Priority date: 1999-07-08
Filing date: 1999-07-08
Publication date: 2001-01-18
Also published as: AU4648599A

Abstract

Control system for milling processes, which comprises at least one self-moving device (5) consisting of transport means (6) whereon at least one collecting mechanism (12) and at least one granulometer (10) are mounted, respectively suitable for taking and analyzing ground product samples from one or more mills (2), said self-moving device (5) being connected to at least one control computer (1) suitable for receiving the results of the analysis carried out by said granulometer (10). The present invention relates also to a self-moving device suitable for being used in said control system.

Description

"SYSTEM AND SELF-MOVING DEVICE FOR THE CONTROL OF

MILLING PROCESSES"

The present invention relates to a system for the control of milling processes, and particularly to a system which can be used for carrying out the particle-size analysis of the ground products of a milling plant and for regulating this plant automatically on the basis of the results of said analysis. Further, the present invention relates to a self-moving device suitable for being employed in such a control system. A control system for milling processes is known, which comprises a multiplicity of complicated and expensive mechanical devices arranged after the mills, each device comprising a multiplicity of sieves and electronic scales suitable for weighing the amount of ground product passing through said sieves.

A computer appropriately modifies the milling parameters of one or more mills by comparing data sent from said scales with the ones stored in an internal table.

However, this known system cannot determine the qualitative grade of the product coming out from the examined mill, since it is not possible to quantify the percentage by weight of the various by-products which are unavoidably generated in different amounts by every mill. Therefore, it appears that the ground product quality can be determined with the known system only at the end of a milling process by traditional methods of laboratory analysis, resulting in the need to interrupt the operation of the milling lines and to regulate by hand not only the milling parameters, but also the ones for system analysis.

In order to avoid these disadvantages, a control system has been conceived, based on particle-size analysis of ground product samples taken after every mill and sent, by means of pneumatic transport lines, to a multiplicity of sieves and electronic scales.

This second known system is more complicated to be manufactured and maintained than the former system and besides, because of its high hindrance and cost, it cannot be used in all the phases of the milling processes and therefore provides approximate results which again require a manual intervention of the millers in order to obtain a ground product having the desired features.

Other disadvantages of said second known system lie in that the particle- size analysis carried out by the sieves takes a long time and consequently the system reaction is slow, and in that dust can settle during transport of the ground product samples and alter particle-size analysis results.

Further disadvantages of the known systems lie in that their use requires remarkable building modifications to the already existing milling plants and anyway does not avoid the necessity to interrupt from time to time the operation of said plants in order to regulate by hand the milling parameters. Object of the present invention is therefore to provide a control system which is free from all the above disadvantages. Said object is achieved by means of a control system and a self-moving device whose main features are disclosed in claims 1 and 3 respectively, while other features are disclosed in the remaining claims. By virtue of the self-moving device comprising a collecting device and a granulometer, whose data are processed by a computer, the control system according to the present invention is able to analyze the ground product particles obtained by different mills without interrupting the milling processes.

Further, thanks to the particular arrangement of the collecting and opening devices above the automatically guided carriage with which it is provided, the self-moving device of the control system according to the present invention has a reduced hindrance, and therefore it is able to move with agility inside the milling rooms wherein spaces are often limited, even if they are generally provided with a certain geometric symmetry. Moreover, said agile movements of the self-moving device are facilitated by maneuver sensors, preferably comprising a camera and an ultrasonic telemeter connected to the internal computer, which allow the position of the self-moving device to be precisely recognized and consequently a precise movement of the device itself to be obtained. Said agility is further improved by the particular structure of the automatically guided carriage, which comprises two independent frames provided with driving and steering wheels, each frame comprising four wheels arranged with their axes substantially parallel and substantially perpendicular to the axes of the wheels of the other frame. Each frame can therefore be alternatively activated in order to modify of 90° the feed direction of the self-moving device without moving it.

Another advantage of the system according to the present invention lies in the particular granulometer used which, especially by virtue of the digital high- resolution camera, allows precise and quick particle-size analysis to be obtained, starting from a minimum resolution of about 50μm in comparison with about 150μm of the known optical granulometers. In confirmation of said rate, a particle-size analysis cycle, comprising opening of the door leading to the mill, taking, analyzing and returning a ground sample, as well as closing said door, has been checked by practical tests to last on the whole only about 60 seconds.

Thanks to this high analysis rate, the control program of the central computer of the system according to the present invention is able to modify in a short time the milling parameters according to the result of the processing of the results of the analyses made by the granulometer. By this measure, a feedback system can be obtained, which is able to regulate said milling parameters with minimum delays and high accuracy, without interrupting the operation of the milling plant.

Another advantage of the system according to the present invention is represented by the particular vibrating chute feeder of the granulometer, which allows a fine disgregation of the ground product particles to be obtained, even when used in wet environments. Further advantages of the system according to the present invention consist in that it can be adapted for the existing milling lines in an easy and relatively economic way, possibly in combination with an already installed control system of known kind, as well as in the particular maneuver versatility of the sample collecting mechanism and of the opening mechanism of the doors leading to the mills.

From the above considerations, the system according to the present invention appears to allow an integrated control of milling processes to be obtained, pursuing in the same time the highest yield while maintaining the desired quality standards.

Further advantages and features of the system according to the present invention will appear to the persons skilled in the art from the following detailed description of an embodiment thereof, with reference to the accompanying drawings, wherein:

- Figure 1 shows a scheme of the system according to the present invention;

- Figure 2 shows a partially sectioned front view of one embodiment of the self-moving device employed in the system of Figure 1;

- Figure 3 shows a top view sectioned along plane III-III of the self-moving device of Figure 2;

- Figure 4 shows a front view of the interior of the granulometer of the self- moving device of Figure 2; - Figure 5 shows a top view of the self-moving device of Figure 2 without the container of the maneuver sensors and the internal computer;

- Figure 6 shows a side view of the collecting mechanism of the self-moving mechanism of Figure 6;

- Figure 7 shows a top view of the collecting mechanism of Figure 6; - Figure 8 shows a partially sectioned side view of the opening mechanism of the self-moving device of Figure 2; and

- Figure 9 shows a top view of the opening mechanism of Figure 8.

With reference to Figure 1, the present embodiment of the system according to the present invention is shown to comprise in a known way a control computer 1 comprising a particle-size analysis program and a control program for the milling parameters of one or more mills 2. The modification of the milling parameters of mills 2 is carried out in a known way by a multiplicity of regulating mechanisms 3, which are connected to computer 1 by lines 4 for the transmission of the relevant control signals. The system according to the present invention suitably comprises at least one self-moving device 5, which is provided with transport means consisting of an automatically guided carriage 6 operated by one or more electric motors, as it will be described later in detail. The operation of carriage 6 and of other mechanisms of the self-moving device 5 is controlled by an internal computer 7, which is radio-connected to control computer 1 by means of a pair of digital transceivers 8, 9.

With reference also to Figure 2, computer 7 inside the self-moving device 5 is shown to be further connected to a granulometer 10 and to an opening mechanism 11, both being arranged above carriage 6. A collecting mechanism 12 and a substantially cylindrical container 13, wherein are arranged internal computer 7 and one or more maneuver sensors, particularly comprising a camera 14 and an ultrasonic telemeter 15, also connected to internal computer 7, are arranged above granulometer 10 and the opening mechanism 11. These maneuver sensors are suitable for determining the position of the self-moving device 5 inside the milling rooms and for guiding it by avoiding obstacles which could stand on the way during its movement from one position to another. For this purpose, electric signals being output by camera 14 and telemeter 15 are transmitted to internal computer 7, wherein topographies of the lamination rooms, the position of mills 2, as well as areas that can be covered by the self-moving device 5 can be stored in digital form. The possible detection of an obstacle by these sensors causes the immediate stop of the self-moving device 5 which lasts for the whole period of permanence of said obstacle on the feed path thereof. In other embodiments of the present invention the control of the movement of the self-moving device 5 can be carried out also by a control keyboard connected to carriage 6 by means of a cable, so that it can be operated by a worker positioned near the device itself

Container 13 for maneuver sensors 14, 15 and for internal computer 7, as well as collecting mechanism 12 are sustained by a bridging structurelό which is mounted on carriage 6 and is preferably provided with closing bulkheads (not shown in the figures) suitable for protecting collecting mechanism 12 and opening mechanism 11 during the movement.

Now, referring also to Figure 3, carriage 6 is shown to comprise two sets of wheels 17, 17', each set comprising four wheels arranged with their axes substantially parallel to each other and substantially perpendicular to the axes of the wheels of the other set. A pair of wheels of each set 17, 17' is able to steer by virtue of pairs of angle arms 18, 18' hinged to threaded sleeves 19, 19' sliding along screws 20, 20', which can be rotated around their axes by electric motors 21, 21 '. The other pair of wheels of each set 17, 17' is driving thanks to a pair of motor reducers 22, 22'. In order to activate one set of wheels and disactivate the other one, so as to suddenly change of 90° the movement direction of the self- moving device 5, carriage 6 suitably comprises a supporting frame 23, whereto the set of wheels 17' is integral, together with the relevant steering means 18', 19', 20', 21 ' and driving means 22'. The other set of wheels 17 and the relevant steering means 18, 19, 20, 21 and driving means 22 are on the contrary integral with a movable frame 24 which can be vertically transferred with respect to supporting frame 23 by means of an electric motor 25 integral with movable frame 24. Motor 25, by means of a gear 26 and a chain 27, operates a pair of shafts 28, 28' which rotate inside pairs of bearings 29, 29'of movable frame 24. Some cams, suitable for rotating against counterplates 30, 30' integral with supporting frame 23, are arranged next to the ends of said shafts 28, 28' so that movable frame 24 can be raised or lowered with respect to supporting frame 23 on the basis of the rotation angle of shafts 28, 28'. The transfer direction of movable frame 24 with respect to supporting frame 23 is kept vertical by a multiplicity of cylindrical guides 31. Finally, in the middle of carriage 6 there is a housing 32 for the 24V direct current rechargeable power supply batteries of motor reducers 22, 22' as well as of all the electric and electronic equipment of the self-moving device 5.

With reference also to Figure 4, there is shown that granulometer 10 is arranged inside a substantially parallelepiped container 33 of the self-moving device 5 and comprises a funnel 34 connected to a vertical pipe 35 which crosses container 33. The lower end of pipe 35 is inserted in a sleeve 36 which can be vertically moved by a screw servomechanism 37 in order to adjust the capacity of ground product entering the granulometer according to the particle size of the ground product itself. Under sleeve 36 there is provided a first chute 38, which hangs from a pair of flat springs 39 in order to be horizontally vibrated by a first electromagnetic vibrator 40. Chute 38 has its outlet over a second chute 41, also fastened to a pair of flat springs 42, but in order to be vertically vibrated by a second electromagnetic vibrator 43. Finally, chute 41 has its outlet over a third chute 44, which again hangs from a pair of flat springs 45, so that it can be horizontally vibrated by a third electromagnetic vibrator 46. The vibration frequencies and/or amplitudes of vibrators 40, 43, 46 and consequently of vibrating chutes 38, 41, 44 are preferably increasing, in order to increase the transportation velocity and to thin as much as possible the layer of particles conveyed by them.

Container 33 is provided with an opening 47 arranged under the outlet of third chute 44, wherethrough the ground product can pass after having crossed the field of vision 48 of a digital camera 49 comprising a high-resolution CCD sensor, such as a sensor able to provide 10 images per second, each one of 1.300.000 pixel, wherein the camera objective is set so that the size of one pixel correspond to about 30 μm x 30 μm. The images of the falling ground product particles, contrasted by a luminescent screen 50 formed for example by a luminescent diode matrix, are converted in digital form by camera 49 and sent to internal computer 7, which comprises an electronic card commonly known as frame grabber. Besides checking the operation of camera 49 and of luminescent screen 50, said card scans the images in order to obtain a data matrix to be stored in a suitable RAM memory for the subsequent analysis, as it will be explained in detail later on. Now, with reference to Figures 5 to 7, the collecting mechanism 12 is shown to comprise a pair of electrical motors 51, 51 ', controlled by internal computer 7 and mechanically connected by means of mitre wheel gearing respectively to a horizontal rail 52 and to container 13, which can be thus rotated in a mutually independent way around the central vertical axis of the self-moving device 5.

A longitudinal screw 53, which can be rotated by a pulley 54 connected to another electric motor 55 by means of a belt 56, is arranged inside horizontal rail 52. A carriage 57 provided with a threaded hole traversed by said screw 53 can slide along rail 52 according to the direction of rotation of the screw itself An oscillating support comprising another electric motor (not shown in the figures) suitable for rotating a lever 58 around a vertical axis, is hinged on a horizontal axis at the base of carriage 57. Said oscillating support comprises also a pair of flanks 59 whose external upper ends are provided with a roller 60 suitable for sliding on the lower surface of rail 52. A pair of horizontal cylindrical guides 61 ending with a L-shaped plate 62, start from said oscillating support A pair of bored blocks 63, 63' whereto the free end of lever 58 and an arm 64 are hinged, can slide along guides 61 This arm final parts end respectively with a tooth 64' and with a cup 65, whose bottom 66 can be opened by virtue of a servomechanism 67 which can rotate the two halves forming said bottom around vertical parallel axes. A pneumatic device (not shown in the figures), suitable for ejecting the ground product collected under opening 47 by one of the two ejecting pipes 68, 68', is provided inside container 33 of granulometer 10.

Finally, with reference to figures 8 and 9, there is shown that opening mechanism 11 of the self-moving device 5 is able to rotate around a vertical axis at the center of a circular basis 69 thanks to a first motor reducer 70 whose gears are arranged in a crankcase 71 Further, a second motor reducer 72 whose gears are arranged in another crankcase 73 is arranged inside opening mechanism 1 1 Said second motor reducer 72 is intended to cause the rotation of an arm 74 whose free end is hinged to the end of a lever 75 At the free end of lever 75 there is arranged a triangular plate 76 whereon three suction cups 77 and three spacing pins 78, suitable for preventing an excessive compression of suction cups 77, are mounted The inclinations of lever 75 and consequently of plate 76 are regulated by a rod 79 whose ends are hinged respectively to a central part of lever 75 and to the free end of another lever 80 having its fulcrum at the opening mechanism 11 During the use, one or more self-moving devices 5 put into circulation along the milling lines by the relevant automatically guided carriages 6 so as to periodically control the particle size of the products ground by each mill 2. Once arrived to a mill 2, the motor reducer 71 rotates the opening mechanism 1 1 of a self-moving device 5 until it is arranged in front of a door leading into the mill. In order to approach this door in a precise way, the self-moving device 5 can raise or lower movable frame 24 of carriage 6 by operating motor 25, so that the set of wheels 17 or 17' turned towards the door itself is laid on the ground. The door is opened by suction cups 77 operated by motor reducer 72, after having been shaken in order to avoid emissions of ground product to the outside.

At this point motor 51 of the self-moving device 5 rotates horizontal rail 52 of collecting mechanism 12 until it is aligned in front of the door, while motor 55 extends carriage 57 outwards, so that guides 61 are inclined downwards as a result of the profile variation of the lower surface of rail 52. By rotating lever 58, arm 64 slides along guides 61 inside mill 2 through the relevant inlet door and arranges itself horizontally when tooth 64' hits against plate 62. Once cup 65 has been filled with the ground product to be analyzed, arm 64 is retracted by an operation sequence inverse with respect to the above described one.

Motor 51 aligns cup 65 above funnel 34 by rotating rail 52, so that the ground product collected by cup 65 is introduced into granulometer 10 through pipe 35 by operating servomechanism 67. Said ground product, carried by chutes 38, 41 and 44 which vibrate at increasing frequencies and/or amplitudes, is disintegrated in a thin layer of particles which are filmed by camera 49 while they are falling from the third chute 44 into opening 47.

The ground product is therefore collected by the pneumatic device and ejected into mill 2 through one of the two ejecting pipes 68 and 68' and the inlet door. The latter is closed at the end of the analysis in granulometer 10 with a sequence of operations of the opening mechanism 11 inverse with respect to the above described one.

Said particle size analysis of the ground product comprises converting and scanning in digital form the images of the falling ground product particles, so as to obtain in the RAM memory of internal computer 7 a data matrix corresponding to said images. From said data matrix the computer calculates, by an algorithm based on the count of contiguous obscured pixel in one or more consecutive images, a statistical table containing the percentage distribution of the particles analyzed as a function of their size. In facts, a ground product particle corresponds to a group of contiguous obscured pixel, and therefore the size of the area covered by the particle, that is the number of obscured pixel, correspond to the size thereof.

On the basis of said statistical table obtained through transceivers 8, 9, the particle-size processing program of control computer 1, with a possible visual check of the operator controlling this computer, can find the optimal milling parameters of mills 2, which are then sent to control mechanism 3 through lines 4 in order to be implemented in a short time in the milling plant.

Claims

1. Control system for milling processes, characterized in that it comprises at least one self-moving device (5) provided with transport means (6) whereon at least one collecting mechanism (12) and at least one granulometer (10) are mounted, respectively suitable for taking and analyzing ground product samples from one or more mills (2), said self-moving device (5) being connected to at least one control computer (1) suitable for receiving the results of the analysis carried out by said granulometer (10).

2. Control system according to the preceding claim, characterized in that said control computer (1) comprises a program suitable for modifying the milling parameters of one or more regulating mechanisms (3) of said mills (2) according to the result of the processing of the results of the analyses carried out by said granulometer (10).

3. Self-moving device (5) suitable for being employed in a control system according to one of the preceding claims and comprising transport means (6) whereon at least one collecting mechanism (12) and at least one granulometer (10) are mounted, characterized in that it comprises at least one internal computer (7), suitable for being radio connected to the control computer (1) of said control system by a pair of digital transceivers (8, 9).

4. Self-moving device (5) according to the preceding claim, characterized in that said transport means (6) consists of an electric-driven automatically guided carriage whose movement is controlled by said internal computer (7) on the basis of signals transmitted by one or more maneuver sensors (14, 15) and of data stored in digital form corresponding to the topographies of the milling rooms, to the position of the mills (2) and/or to the areas that can be covered by the self- moving device itself.

5. Self-moving device (5) according to the preceding claim, characterized in that said maneuver sensors comprise a camera (14) and an ultrasonic telemeter (15).

6. Self-moving device (5) according to one of claims 3 to 5, characterized in that said transport means (6) comprises two sets of wheels (17, 17') each set comprising four wheels arranged with their axes substantially parallel to each other and substantially perpendicular to the axes of the wheels of the other set, one pair of wheels of each set (17, 17') being steering and the other pair of wheels of each set (17, 17') being driving, wherein said transport means (6) comprises a supporting frame (23) whereto one set of wheels (17') with the relevant steering means (18', 19', 20', 21') and driving means (22') is integral and a movable frame (24) whereto the other set of wheels (17) with the relevant steering means (18, 19, 20, 21) and driving means (22) is integral, wherein said movable frame (24) can be vertically transferred with respect to said supporting frame (23).

7. Self-moving device (5) according to one of claims 3 to 6, characterized in that said granulometer (10) comprises one or more vibrating chutes (38, 41, 44) suitable for disgregating said ground product samples in thin layers of particles which are filmed by a digital camera (49) while they are falling from said vibrating chutes (38, 41, 44).

8. Self-moving device (5) according to the preceding claim, characterized in that said digital camera (49) comprises a high-resolution CCD sensor which is able to provide at least 10 images per second, each one of at least 1.300.000 pixel, wherein the camera objective is set so that the size of one pixel corresponds to about 30 μm x 30 μm.

9. Self-moving device (5) according to claim 7 or 8, characterized in that the images of the falling ground product particles, contrasted by a luminescent screen (50), are converted in digital form by a camera (49) and sent to internal computer (7), which comprises an electronic card which scans the images in order to obtain a data matrix for the particle-size analysis.

10. Self-moving device (5) according to the preceding claim, characterized in that the internal computer (7) calculates, by means of an algorithm based on the count of contiguous obscured pixel in one or more consecutive images obtained by the camera (49) a statistical table containing the percentage distribution of the particles analyzed as a function of their size.

11. Self-moving device (5) according to claim 7, characterized in that said vibrating chutes (38, 41, 44) comprise at least a first chute (38) suitable for vibrating horizontally, which has its outlet over a second chute (41) suitable for vibrating vertically, which in turn has its outlet over a third chute (44) suitable for vibrating horizontally.

12 Self-moving device (5) according to claim 7 or 11, characterized in that the vibration frequency and/or the amplitude of each one of said vibrating chutes (38, 41, 44) is lower than the vibration frequency and/or amplitude of the following vibrating chute.

13 Self-moving device (5) according to one of claims 3 to 12, characterized in that said collecting mechanism (12) comprises one horizontal rail (52) suitable for rotating around the central vertical axis of the self-moving device (5), along which a carriage (57) can slide, whereto an oscillating support (59) for an extensible arm (64) ending with a cup (65) suitable for collecting the ground product to be analyzed, is hinged.

14 Self-moving device (5) according to one of claims 3 to 13, characterized in that it comprises pneumatic means suitable for ejecting from one or more ejecting pipes (68, 68') the ground product sample taken by said collecting mechanism (12)

15 Self-moving device (5) according to one of claims 3 to 14, characterized in that it comprises at least one opening mechanism (11) suitable for opening the doors leading into the mills (2)

16 Self-moving device (5) according to one claims 3 to 15, characterized in that said opening mechanism (11) comprises a first motor reducer (70) suitable for rotating the mechanism itself around a vertical axis.

17. Self-moving device (5) according to one of the preceding claims, characterized in that said opening mechanism (11) comprises a second motor reducer (71) suitable for rotating around horizontal axes a lever system (75, 76, 79, 80) comprising a lever (75) having one end provided with one or more suction cups (77) suitable for adhering to the surface of the doors leading into the mills (2).