This application claims priority to Spanish Patent Application No. P201830223 filed Mar. 8, 2018, the disclosure of which is hereby incorporated by reference in its entirety.
The present disclosure relates to a method for optimizing a motor load during a shredding process in a shredder for metal materials, such that the rotational speed of the motor is adjusted as a function of the rotational speed of the rotor of the shredder and as a function of the interaction with the hydraulic clutch that relates the motor to the rotor. The method can be applied to the industry of machinery for recycling and shredding, specifically to the industry of machinery designed for shredding materials, and more specifically to the industry of machinery designed for shredding metal materials.
Currently, shredders for metal materials receive large amounts of material in the shredding chamber, where the shredding mill is located, and this material must be shredded in order for the shredder to continue working. However, feeding the shredding chamber is not done in a uniform way and there are variations in the input of material, thus, shredding in the chamber is not done uniformly or in a consistent way, which leads to excess work or moments in which the shredder works below its shredding potential.
To regulate the workload of the motors for shredders known in the state of the art, the input of metal material to be shredded is usually controlled, and in the case of an excess load, the introduction of the metal material is stopped until the mill is capable of shredding the metal material inside the shredding chamber, at which time metal material is once again introduced in the aforementioned shredding chamber. Occasionally this type of control is entirely manual and causes the motor to be subjected to variations in the workload, and as a result, it sometimes works above its capacity and other times below its capacity. This system of control can also be automatic, the feeding being controlled as a function of the motor load, which is common in shredders.
Furthermore, in shredders for metal materials known in the state of the art, between the motor of the shredder and the rotor of the mill there is a hydraulic clutch with a variable flow that protects the motor and all of the elements situated after the clutch itself when excess power is produced in the motor. For example, when the mill has an excess material load and demands the maximum torque from the motor, the motor will react by providing said torque at an established work speed. If the torque demanded is greater than the maximum torque provided by the motor, the motor could stop (in the case that the clutch is weighted above the demands of the motor), leading to jams in the mill which will require time and resources to solve. In these situations the mill loses efficiency.
The hydraulic clutches known in the state of the art and applied to shredding machines are made up of two facing crowns with vanes, between which a hydraulic fluid circulates, which transmits the movement of one crown to the other, in other words, one crown rotates based on the movement of a motor and the hydraulic fluid transmits the rotational movement of the crown of the motor to a second crown associated with the rotor of the mill of the shredder.
In other words, if there is a difference in speed between the crown associated with the rotor of the mill and the crown associated with the motor of the shredder, said difference in speed is absorbed by the hydraulic clutch by means of the hydraulic sliding of the clutch itself. Specifically, when one crown rotates less than the other one, the hydraulic fluid absorbs the difference in speeds between the crowns.
The hydraulic sliding in the hydraulic clutch generates an increase in the temperature of the hydraulic fluid inside the clutch. This increase in temperature makes it necessary to cool the hydraulic fluid, resulting in a loss of power of the cooling system. Thus, the greater the sliding, the greater the increase in the temperature of the hydraulic fluid, leading to a greater need for cooling, which implies an increase in the loss of power of the system.
In clutches of shredders known in the state of the art, when the motor of the shredder starts up, it does not contain any hydraulic fluid on the inside of the same, meaning the motor starts up idle, and once the working conditions of the motor are reached, the hydraulic fluid is introduced in the clutch in a progressive way. This causes a progressive load of hydraulic fluid in the clutch and a power transfer to the output shaft, where the output pulley is located which in turn transmits the movement to the rotor of the mill. Furthermore, the hydraulic fluid enters and exits the clutch, and when the hydraulic fluid reaches a specific temperature it is necessary to cool the same in order to keep it at a suitable working temperature.
Considering all of the foregoing points, specifically the cooling problem in the hydraulic clutch, for the correct operation of the clutch itself and for the power to be correctly transmitted between the two parts of the clutch, the hydraulic sliding of a clutch is considered optimum when the value thereof is approximately 3%.
The object of this disclosure is a method for optimizing the workload of a motor in a metal shredder that regulates the rotational speed of said motor as a function of the rotational speed of the rotor of the shredder, thereby obtaining a better use of the properties of the motor and reducing the sliding, thereby reducing the power loss of the system.
The disclosure teaches a method for optimizing a motor load during a shredding process in a metal shredder, wherein the shredder comprises a rotor of a shredding mill and a motor with a hydraulic clutch between the rotor and the motor.
The method object of the disclosure comprises the following steps:
In the step of calculating a modified speed based on the speed measured in step A in the method for optimizing a motor during a shredding process in a metal shredder object of the disclosure, the speed that is obtained is the speed of the rotor increased by 3% to 10%.
The object of this disclosure is a method for optimizing the motor load during a shredding process in a metal shredder, thereby optimizing the efficiency of the motor, and at the same time reducing the energy dissipated in the form of heat by sliding in the operation of the shredder.
A metal shredder, in a very basic way, comprises a feeding system in which metal materials are fed to the shredder (to which we will not refer in this description given that it is not of interest in the method object of the disclosure), a shredding chamber (which, in turn, comprises a shredding mill that rotates on a rotor, with a plurality of hammers on the periphery of the mill, which on the inside of the chamber thrash the metal material in order to shred it) and an extraction system for the shredded metal material (to which we will not refer in this description given that it is also not of interest in the method object of the disclosure).
The method object of the disclosure is based on continuously controlling the relationship between the speed of the motor of the shredder and the speed of the rotor during the shredding process.
First, to interpret this specification, it would seem appropriate to define the motor load as the motor torque that a motor must supply in order to overcome the resistance that is opposed to the movement thereof, and, as can be seen in
The method for optimizing the load of a motor during a shredding process in a metal shredder object of the disclosure in the preferred embodiment of the same comprises the following steps:
With the method object of the disclosure the motor load is optimized during the shredding process in a continuous way, meaning the control of the speed of the rotor and the modification of the speed of the motor is continuous during the shredding process, this way, the speed of the motor is adjusted to the speed of the rotor at all times as the motor demands more or less torque in order to shred the materials that are inside the shredding chamber of the shredder.
Due to the design thereof, each motor has its own torque curve that shows the torque offered by the motor as a function of the rotational speed of the motor itself. From a study of this torque curve, in the design phase it is decided which speeds are acceptable for the motor to work at for said application. If taking the motor of
We can define that the speeds at which we want the motor to work are those at which the torque supplied by the motor is no less than the nominal functioning torque at the normal speed regime (1800 r/min in
Thus, to optimize the motor load, it is recommended that the motor work in the previously established speed range, both for making the best use of the motor and for maintenance of the same, since with the method object of the disclosure, the motor of the shredder always works at a speed within the best operating range of the same. This way, the problems of wear and possible malfunctioning are reduced with respect to motors that work at varying speeds.
As such, in the method object of the disclosure, the speed calculated based on the measured speed of the rotor, in other words, the speed that is applied to the motor of the shredder, is within the speed range of the motor which, within the torque curve of the motor, is within the area of the aforementioned curve where the motor torque is maintained between values that are previously established in the design phase.
With this condition, the operation of the shredder is completely optimized, given that the beginning of the operation of the hydraulic clutch establishes that the output torque and the input torque are maintained in their entirety.
With the speed modification of the motor we ensure a controlled sliding in the clutch for transmitting the operating torque of the design of the motor, avoiding a degree of power that the clutch could not transmit without sliding and thereby preventing additional heat from being generated by an excessive sliding of the clutch.
Thus, the method object of the disclosure carries out a dual control of the optimum speed of the motor of the shredder, since it controls for both the maximum sliding of the clutch and for torque demanded from the motor.
Considering the foregoing points, there are two situations in which either the control by sliding or control by torque demanded predominates. Said situations are:
With the method object of the disclosure, the following advantages are obtained:
The disclosure is not intended to be limited to the specific embodiment described in this document. Those skilled in the art may develop other embodiments in light of the description made herein. As such, the scope of the disclosure is defined by the following claims.
Number | Date | Country | Kind |
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P201830223 | Mar 2018 | ES | national |