SALDA, Luciano (Via Roma 11, Vignola, Province Of Modena, I-41058, IT)
| CLAIMS
1. Apparatus for automatically regulating the action of the constriction means arranged on the discharge mouth (3) of screw presses for example of the type used for compressing waste, the said constriction means being formed by at least one pivoting hatch (8), characterized in that said hatch is controlled, during pivoting, by a servocontrol device or actuator of any suitable - preferably irreversible - type and in that means are envisaged for detecting in any suitable manner the force which the material pushed by the press exerts against the said constricting hatch and for generating a corresponding electric command or signal which is sent to a microprocessor unit (29) which drives the said servocontrol device and which is also preset to detect the value of the current used by the electric motor of the reduction gear unit (31 ) for rotation of the screw (2) of the press and to compare this current value with threshold operating and safety values which are programmed in it, there being envisaged means for ensuring that this microprocessor unit is able to regulate automatically opening of the constricting hatch of the press so as to keep the current used by the motor of the said press within operating values and ensure that, if the said current tends to exceed a predetermined safety value, the apparatus increases automatically opening of the constricting hatch, and, if the said problem persists, the press is stopped and its screw is temporarily made to assume a reverse rotation condition in order to carry out one or more attempts at unblocking it, following which the said press returns to the normal operating cycle.
2. Apparatus according to Claim 1 , in which the said servocontrol device or actuator which controls the pivoting movement of the hatch (8) about its fulcrum (7) is of the type which comprises a female thread (21 ) hinged on the end of lever arms (12) for actuating the said hatch (8) and which co-operates with a screw (22) which passes, in a freely rotatable manner and via one or more thrust bearings (25), through a support block (23) pivotably hinged with support means (24, 6) fixed to the body of the screw, there being fixed to said support means a reduction gear unit (26) with an electric motor rotating in both directions, for operating the said screw (22).
3. Apparatus according to Claim 1 , in which the means which detect the force exerted against the constricting hatch (8) by the material pushed by the press and which generate a corresponding electric command or signal envisage that the lever arms (12) connected to the actuator are hinged on the same hinging pin (7) as the hatch (8) and also envisage that the two parts are connected together by resilient means (14) which are compressed when the said hatch is pushed by the material discharged by the press, the relative pivoting of the hatch and the said lever arms (12) being detected by one or more sensors (16, 16') connected to the said microprocessor unit (29).
4. Apparatus according to Claims 1 , in which the means which detect the force exerted against the constricting hatch (8) by the material pushed by the press and which generate a corresponding electric command or signal comprise at least any one suitable load cell positioned at any suitable point along the kinematic chain which connects the hatch (8) to the associated servocontrol device or operating actuator.
5. Apparatus according to Claim 1 , in which optional sensors (27, 27') or linear or angular transducers may be envisaged for transmitting to the microprocessor unit (29) an electric signal correlated to at least the end positions of the hatch (8) relative to the discharge mouth (3) of the press.
6. Apparatus according to claim 1 , in which means are envisaged for ensuring that, at the end of each working cycle of the machine, the constricting hatch (8) may be brought into the fully open position in order to facilitate cleaning or self-cleaning of the residual material from the screw (2).
7. Apparatus according to claim 1 , in which the end part (101 ) of the body (1 ) of the press is occupied along nearly the whole of its length by the rotating screw (2) such that the final part of the latter is situated at a short distance from the discharge mouth (3) of the said press, in order to limit the formation of residual plugs of material in this mouth and facilitate cleaning of the said discharge mouth. |
TITLE
"Apparatus for automatically regulating the action of the constriction means arranged on the discharge mouth of screw presses" DESCRIPTION The invention relates to screw presses for example of the type used in waste compressing machines, with a tubular body which has a diameter usually decreasing towards the discharge mouth and is closed at the other end and provided with longitudinal grooves and which has, coaxially rotating inside it, a screw usually with a pitch decreasing towards the discharge mouth, the shaft of which protrudes axially and rotatably from the closed end of the said body and is connected to a reduction gear unit flanged to this body and operated by an electric motor of suitable power rotating in both directions. At the closed end, the body of the press is open laterally, towards the top, and communicates with a hopper for feeding the material to be pressed, while at the discharge end the said body has means for constricting its discharge mouth, which offer a suitable resistance to the material transported by the screw, so that it emerges suitably compacted. These constriction means are at present opposed by resilient means set to a predetermined value, also depending on the characteristics of the material to be compacted and, when the thrust of the material overcomes the action of these means, the discharge mouth opens by a proportional amount so as to favour discharging of the compacted material. In a screw press which for some time has been produced by the applicant, constriction of the discharge mouth of the press is obtained by means of a pivoting hatch which is forced to shut by adjustable resilient means. In the presses of the known type it is also envisaged that the last part of the press body, which ends in the discharge mouth, is not occupied by the screw over a section of suitable length and that it is cylindrical or slightly conical so as to favour the accumulation and compression of the material along this last section of the press body, before the material itself comes into contact with the said constricting hatch. In the presses in question means are also envisaged for controlling the current used by the electric motor operating the screw and for ensuring that, when predetermined
maximum consumption values are reached, the said motor is stopped and is made to rotate temporarily in the opposite direction to the operating direction, while the constricting hatch of the discharge mouth remains in the predetermined maximum calibrated condition. In the present systems there is no interactive link between the operating force of the press motor and the calibration force of the constriction means which act on the discharge mouth of the said press, so that these systems are often difficult to regulate and often result in continuous reversal of operation of the screw and consequent inactivity of the press. In addition to this drawback there is the fact that the last section of the press body, which is not occupied by the screw, at the end of each working cycle of the said press, should be cleaned in order to prevent the formation inside it of a plug which, solidifying, would then prevent subsequent operation of the same press, in particular when the latter must compress waste containing liquids and cardboard or other paper or organic materials containing sticky components. In order to perform cleaning of this final section of the press, at present it is required to modify the calibration of the constricting hatch of the discharge mouth, by means of a long, difficult and problematic operation, also because it requires subsequent re-calibration of the resilient opposition means of the said hatch. It often happens that the personnel responsible for using the press do not perform said cleaning, with the consequences which can be imagined. The invention intends to overcome these and other drawbacks of the prior art, by means of an apparatus as described in the accompanying claims, based on the following proposed solution. The pivoting constricting hatch of the discharge mouth of the press is controlled, during pivoting, by an actuator which is of any suitable - preferably irreversible - type and means are envisaged for detecting in any suitable manner the force which the material pushed by the press exerts against the said constricting hatch and for generating a consequent electric command and/or signal. This command or signal is transmitted to a microprocessor unit which drives the said servocontrol device and which is also preset to detect the value of the current used by the electric motor of the reduction gear unit for rotation of the screw of the press and is also preset to compare this current value with threshold operating and safety
values which are programmed in it. The microprocessor unit automatically regulates opening of the constricting hatch of the press so as to keep the current used by the motor of the said press within operating values. If, during operation of the press, the processor detects that the motor of the said press has a current consumption value which tends to exceed a predetermined safety value, the apparatus tries to increase opening of the constricting hatch to the fully open position and, only if after a predefined number of attempts the said problem persists, the screw of the press is stopped and is temporarily made to assume a reverse rotation condition in order to carry out one or more attempts at unblocking it, following which the said press returns to the normal operating cycle.
With this solution, the apparatus automatically adapts itself to the characteristics of the material to be compacted and the oscillating reversal movements of the screw are limited. Owing to the presence of the said hatch with angular positioning which is servo-assisted and related to the force of the press motor, it is also possible to reduce the length of the final section of the press which is free of the screw and arrange the latter very close to the discharge mouth, with the advantage of a reduced need to perform cleaning of the discharge mouth of the press at the end of each operating cycle. These and other characteristic features of the invention and the advantages arising therefrom will emerge more clearly from the following description of a preferred embodiment thereof, illustrated purely by way of a non-limiting example, in the figures of the accompanying plates of drawings, in which:
- Fig. 1 shows a perspective view of the apparatus, with the hatch in the semi-open position; - Fig. 2 shows a side and longitudinally/centrally sectioned view of the apparatus according to Figure 1.
In the Figures, 1 denotes the body of the press and 101 denotes the end part of this body which is also occupied over nearly the whole of its length by the rotating screw 2 such that the final part of the latter is situated at a short distance from the discharge mouth 3 of the said press. 4 indicates partly the longitudinal grooves which extend
over the entire length of the body 1 , 101 of the press. A base piece 5 is integrally fixed onto the end part 101 of the press body and has, fixed thereon, with the possibility of adjustment, a flat base 6 which is oriented with its larger dimension in the direction of the length of the press and which terminates at the discharge mouth 3 with an enlarged head 106 which rotatably supports a pin 7 which supports, pivotably hinged on its projecting ends, two parallel ribs 108 fixed edgewise onto the outer side of the hatch 8 which closes the discharge mouth 3 of the press. Underneath the hinging pin 7, the said ribs 108 are interconnected by a cross-piece 9 which, with its cylindrical ends, is mounted rotatably in corresponding holes of the said ribs 108 and which, on the middle and flattened part, has, fixed perpendicularly and with a symmetrical arrangement, a pair of pins 10 which pass through, with play, corresponding holes in a cross-piece 1 1 which with its ends is fixed or rotatably supported by the bottom end of a pair of flat levers 12 situated inside the said ribs 108 which are also pivotably hinged on the pin 7 and which extend upwards with identical parallel sections interconnected by a cross-member 13. The said pins 10 have, mounted on them, between the cross-pieces 9 and 1 1 , resilient means 14 with suitable characteristics, shown here as cylindrical helix springs, but more preferably consisting of Belleville washers. The section of the pins 10 which protrudes from the top of the cross-piece 1 1 may be provided with a shim 15, if necessary, and terminates in a head 1 10. There exists a suitable degree of freedom of relative pivoting movement of the levers 12 and the ribs 108 with the hatch 8, which occurs in opposition to the action of the said resilient means 14. In order to prevent excessive compressive stressing of the resilient means 14 it may be advantageously envisaged that, after a predetermined maximum pivoting movement, a bottom end section 1 12 of the levers 12 touches the hatch 8.
The pressure stressed or unstressed conditions of the springs 14 is detected by at least one sensor or preferably two sensors 16, 16' for example of the proximity type, which are mounted on respective arms 17, 17' arranged alongside on the outside of the ribs 108, pivotably hinged on the ends of the pin 7 and having, concentrically with the latter, a respective curved eyelet 18 engaged by a screw 19 fixed to the adjacent
rib 108, so as to allow improved relative adjustment of the arms 17, 17' and the associated ribs 108. Purely by way of example it may be envisaged that, when the device is at rest, the sensor 16' is located on the outside of the right-hand side of the associated lever 12 when viewing Figures 1 and 2 and that, when this sensor passes from the OFF state to the ON state, it indicates that the resilient means 14 have been compressed by the thrust of the material discharged from the press against the hatch 8 which has been moved away slightly from the discharging mouth of the press. The sensor 16 which instead works on the left-hand side of the associated lever 12, when it passes from the OFF to the ON state, indicates that the said resilient means 14 have been decompressed and that the hatch 8 has moved slightly closer towards the discharge mouth of the press. This change in the state of the sensors 16 and 16' is used for the functions mentioned further below.
The top end of the levers 12 is interconnected by a cross-piece 20 which with its ends is rotatably supported by the said levers and which has, transversely formed in its middle part, a threaded hole 21 passed through by a screw 22 which in turn passes in a freely rotatable manner through a support block 23 pivotably hinged transversely by means of a pin 123 with a pair of parallel arms 24 integral with the flat base 6. On the support block 23, the screw 22 discharges the axial thrust via at least one thrust bearing 25 which may also be arranged in a position different from that shown in Figure 2 and this support block has, flanged thereto, a reduction gear unit 26 with an electric motor rotating in both directions, for operating the screw 22. The apparatus may optionally be provided with means for detecting at least the substantially closed and fully open end-of-travel position of the hatch 8 and these means may consist, for example, of microswitches 27, 27' which are fixed onto a rod 28 parallel to the screw 22 and in turn fixed with one end to the said support block 23, the said microswitches being such that they may be operated for example by the cross-piece 20 or by the suitably rounded end of one of the levers 12. All the sensors 16, 16' and the microswitches 27, 27' are connected to a microprocessor unit 29 which controls the electric motor of the reduction gear unit 26 by means of a special interface 30 and which also controls operation of the electric
motor of the reduction gear unit 31 for operating the screw 2, via a special interface 32. 33 denotes an interrogation and programming unit which allows dialoguing with the processor 29, also for programming the threshold values of the current used by the motor of the reduction gear unit 31 , in accordance with which the apparatus in question must intervene.
Also owing to a special software which runs in the unit 29, the apparatus as described functions in the following manner. At the start of each cycle, the hatch 8 is situated in or is automatically brought into the closed or substantially closed position of the discharge mouth 3 of the press, as shown in Figure 2 by means of dot-dash lines. This start of cycle condition may be detected by the microswitch 27', where present, or by the sensor 16' which detects compression of the resilient means 14. The reduction gear unit 31 of the press is activated and the material is conveyed and compacted by the screw 2 towards the discharge mouth 3 which is closed by the hatch 8. When the thrust against the hatch 8 of the material which accumulates at the discharge mouth 3 reaches values such as to displace this hatch and stress the aforementioned associated resilient means 14, this displacement is detected by means of the microswitch 16' and is signalled to the processor 29 and, when the latter detects via the interface 32 that the motor of the press unit 31 reaches a predetermined current consumption value, the said processor 29 causes activation of the reduction gear unit 26 so as to increase opening of the hatch 8, until a change in the state of the said sensors 16 and/or 16' occurs and this cycle continues until the value of the current used by the motor of the unit 31 remains within the predetermined ideal operating values, which indicate good compression of the material treated by the press. If, on the other hand, the current value falls below the said ideal programmed value, this means that the press is operating under zero load or that it is discharging, so that it is required to close again by a proportional amount the hatch 8 and this will be performed by the processor 29 via the reduction gear unit 26. The apparatus therefore automatically adapts constriction of the discharge mouth of the press to the characteristics of the material which are in each case treated by the said press and to the operating condition of the said press, without the
need to perform difficult working adjustments, as are instead required by the prior art. If, during operation of the press, the processor detects that the unit 31 of the press reaches a current consumption value tending to exceed a predetermined safety value, the apparatus tries to increase opening of the hatch 8, as far as the fully open position, and if, after one or more predefined attempts, the said problem persists, the unit 31 is stopped and is brought temporarily into a reverse rotation condition in order to carry out one or more attempts at unblocking the screw 2, following which the press returns to the normal operating cycle. It is obvious that, if the adverse working condition of the press occurs again several times at a short interval from each other, means are envisaged for stopping operation of the press and signalling the stopped condition. By means of the unit 33 it will be possible, if necessary, to interrogate the system in order to understand the causes which have led to stoppage of the press. At the end of each working cycle, by operating a special control device (not shown) or automatically, the hatch 8 may be brought into the fully open position detected for example by the microswitch 27, so as to allow self-cleaning or forced and manual cleaning of the discharge mouth 3, even though this operation is now less necessary since the part of this mouth not occupied by the screw 2 is of limited size, so that any plug of material which could form in the latter would be easily evacuated by the action of the said screw 2 upon subsequent reactivation of the press. It is understood that the description refers to a preferred embodiment of the invention, to which numerous constructional variations and modifications may be made, these relating, for example, to the use of an actuator other than a screw and female thread actuator for pivoting of the hatch. A further modification could relate to the fact that the hatch 8 could be integral with the levers 12 and/or that the resilient means 14 and the sensors 16, 16' could be eliminated, using one or more load cells which detect the force to which the said hatch 8 is subjected by the material discharged from the press. The load cell could be arranged at any point along the kinematic chain which connects the hatch 8 to the associated pivoting servocontrol device. An angular or linear displacement transducer may be used instead of any microswitches 27, 27'.