Title of Invention

"A PROCESS FOR SHUTTING DOWN AN ELECTRICAL DRIVE MOTOR,AND A BRAKE CIRCUIT FOR AN ELECTRICAL DRIVE MOTOR"

Abstract

In a process for shutting down an electrical drive motor, in particular a drive motor for driving a cam cylinder of a winding station of a bobbin winding machine, which is subjected to a braking current in the opposite direction to a rated current in order to achieve the braking effect, provision is made for the momentary thermal load of the drive motor to be assessed and the strength of the braking current selected as a function of this thermal load on the drive motor.

Full Text

-1A- PROCESS FOR SHUTTING DOWN AN ELECTRICAL DRIVE MOTOR, AND A BRAKE CIRCUIT The invention relates to a process for shutting down an electrical drive motor, and in particular a drive motor for driving a cam cylinder of a winding station of a bobbin winding machine, which for the purpose of braking is subjected to a braking current in the opposite direction to a rated current, the strength of the said braking current being possibly a multiple of the rated current, and a braking circuit. In many applications of electrical drive motors, every effort is made to bring them to a standstill as quickly as possible. In the case of bobbin-winding machines, for example, in which in each case an electrical drive motor drives a cam cylinder of a winding station, every effort is made to brake the drive motor as quickly as possible if required, in order to keep the shut-down times of the winding stations concerned as short as possible, and therefore to keep the degree of efficiency of the winding machine high. Spinning cops are wound at the winding stations to form large-volume cross-wound bobbins. In this situation, the threads are monitored during the rewinding process for thread defects. If a thread defect is detected, the rewinding process is interrupted, the piece of thread with the defect is cut out, a thread connection is created between the remaining thread pieces, and the winding process is resumed. In order to carry this out in the shortest possible time, it is also necessary for the cam cylinder to be brought to a standstill as quickly as possible. In order to brake an electrical drive motor in an electrical manner, the motor is subjected to a braking - 2 - current in the opposite direction to the rated current. The braking time in this context is dependent on the strength of the braking current, which may amount to a multiple of the rated current, without, under normal circumstances, any risk arising of the drive motor being damaged. Usually, a thermal monitoring device is provided for drive motors of this type, which determine any thermal overload, and then interrupt the operation of the drive motor, so preventing severe motor damage as a result of the motor overheating. Such thermal overload may occur if a drive motor of a cam cylinder is braked and then speeded up again several times in quick succession. The drive motor is then switched off by means of the temperature monitoring device, and remains switched off until the temperature has again fallen below the preset safety value. As a rule, a red light is also fitted to the winding station concerned, which therefore indicates that a fault has occurred at this winding station which requires the intervention of the operating personnel. This leads to shutdown times and not inconsiderable losses in degrees of efficiency of the device or machine concerned. The invention is based on the objective of created a process and a brake circuit of the type described in the preamble, in which the element driven by the drive motor, or the machine pertaining to it, can operate with the highest possible degree of efficiency. This objective is attained in respect of the process by the principle that the thermal loading of the drive motor at any particular moment is assessed, and the strength of the braking current is selected as a function of this thermal loading of the drive motor. The result of this is that, each time a braking procedure is initiated, the strength is assessed of the _ 3 _ braking current which is suitable for the braking process, i.e. the highest possible braking current, with the result that, in the event of several braking processes being repeated at short intervals in succession, it is possible to operate in each case with a maximum braking force which will minimise the braking time, without this leading to the drive motor being overloaded. Depending on the thermal loading of the drive motor at any particular moment, differing braking times will then be obtained; i.e. with higher thermal loading, higher braking times will be incurred, but without the drive motor passing into a temperature range which would require it to be shut off. In order to keep the expenditure on apparatus as low as possible, provision is made in the embodiment of the invention for the thermal loading of the drive motor at a given moment to be determined over time from the current imposition on the drive motor. In this way, the expenditure on measuring technology or apparatus is kept low. In a further embodiment of the invention, provision is made for stepped values to be imposed for the braking currents, to each of which a range of the thermal loading is allocated. For the practical realisation, a stepped appraisal of this nature of the appropriate braking current is sufficient without further ado. With regard to a brake circuit, the objective is achieved by the principle that provision is made for media for the acquisition of the thermal loading of the drive motor at any particular moment, and media for the selection of the braking current to be imposed for a braking procedure as a function of this thermal loading. In a further embodiment, provision is made for media for - 4 - the allocation of the thermal loading value acquired to thermal loading values stored in a memory, and for media for calling up a braking current with a strength specified for the allocated value. Further features and advantages of the invention are explained hereinafter on the basis of embodiments represented in the drawings. These show: Fig. 1 A schematic representation of a first embodiment of a circuit arrangement which contains a brake circuit for a drive motor of a cam cylinder of a winding station for a bobbin winding machine; Fig. 2 A further embodiment of a brake circuit according to the invention. On bobbin winding machines the individual winding stations are in each case equipped with a cam cylinder 10, which, during rewinding, drives a relatively large-volume take-up bobbin by means of friction contact. During the rewinding process, the cam cylinder 10 lays a thread 12, drawn from a spinning cop (not shown) in a transverse direction in such a way that a conical or cylindrical cross-wound bobbin 11 is wound. The cam cylinder 10 is, in this situation, driven by means of an electric motor 13, which, in the embodiment shown, is an electronically-comminuted_ servo-motor. The circuit arrangement with the brake circuit according to the present invention is, however, in principle well-suited for any type of electrical drive motor. If a thread defect is detected, which is to be removed from the thread 12, or a thread break occurs, the winding process is interrupted immediately. This means that the cross-wound bobbin 11 is raised from the cam cylinder 10, and braked to a standstill by means of a bobbin brake arranged at the creel, not shown but inherently known. The cam cylinder 10, which features a not inconsiderable degree of inertia, is likewise braked, inasmuch as the drive motor 13 is subjected to a braking current which is directed in a counter-direction to the direction of the rated current which pertains during normal winding operation. In order to bring the drive motor 13 to a standstill as quickly as possible, a braking current is selected with the highest possible strength, which may amount to a multiple of the strength of the rated current. The thermal load which occurs briefly in this context is not so strong that it can lead to any damage to the drive motor 13. However, if a number of braking procedures need to be carried out within a short period of time, the thermal load of the drive motor 13 may become very high. Usually, drive motors of this type are accordingly provided with thermal over-load protection, which ensures that the drive motor 13, once a satety temperature has been reached, will switch off and cannot, be switched in again. Multiple braking of the cam cylinder 10 within a short period o± time can therefore lead to the actuation of the thermal overload protection, with the result that the drive motor 13 will be shut down sufficiently long for the safety temperature to be again adequately undercut. As a rule, a red light is also located at the winding station concerned, and the operating personnel are therefore warned that a machine error has occurred, while the shutdown periods which this incurs, for - 6 - instance in the case of the embodiment of a winding station given as an example, will lead to a loss of efficiency of the winding station in question, and therefore of the bobbin winding machine. In order to avoid the shutdown times incurred during braking as a result of thermal overload, provision is made, according to the invention, for the thermal load of the drive motor 13 at any particular moment to be assessed, and that, as a function of this load, the strength of the braking current for the following braking procedure is selected in such a way that it will be ensured that no thermal overload can occur. In this way, it is true that it will not always be the shortest theoretically possible braking time which is applied for each braking procedure, but the technically permissible shortest braking time permissible in order to avoid thermal overload of the drive motor 13. In the embodiment according to Fig. 1, a winding station computer 14 specifies the current strength and direction to which the drive motor 13 is subjected. The winding station computer 14 then determines, on the one hand, the revolution speed of the drive motor 13, and, on the other, as a function of the thermal load state of the drive motor 13, its braking behaviour. The winding station computer 14 processes the information from a central computer (not shown), which is provided, for example, by means of a machine bus 21. This information may relate, for example, to the winding speed or the revolution speed of the drive motor 13, and, if applicable, also to the prevention of ribboning on the cross-wound bobbin 11. The signals from the winding station computer 14, which pass via a line 22 to an end stage 15, are processed there accordingly. This means that the end stage 15 - 7 - conducts the current, in correct phase, to the windings of the drive motor 13. To do this, the end stage 15 also assesses information from a rotor location sensor 16. The actual speed determined at a pole ring 17 of the drive motor 13, or the actual revolution speed of the drive motor 13, is signalled back t o the revolution speed regulating system at the winding station computer 14 . The actual speed of the drive motor 13, as assessed, can also be applied for additional functions at the winding station; it may, for example, be conducted to a cleaner, which, depending on the actual speed, determines the measurement interval for monitoring the thread 12. The winding station computer 14 also assessed the information about the thermal loading of the drive motor 13 at any particular moment. As indicated in Fig. 1, a thermal sensor 18 may be allocated to the drive motor 13 for this purpose, the signal from which is input into the winding station computer 14. The winding station computer 14 can, however, as indicated in Fig. 2, also calculate the thermal load of the drive motor 13 at any particular moment, by assessing the current imposition on the drive motor 13 over the particular period of time. The winding station computer 14 in this case features an integrator 20 as well as a memory 19. Deposited in the memory 19, in this situation, there are a large number of drum load value ranges with the braking values which pertain to them. On the basis of this data, the winding station computer 14 then determines the strength of the braking current with which the drive motor 13 may be imposed as a maximum, in such a way that the shortest - 8 - possible braking time will be achieved, but at the same time the braking current will not lead to any impermissible thermal overload of the drive motor 13. It is to the purpose if the limited ranges for the thermal load of the drive motor 13, and the maximum strengths of the braking currents pertaining to that load, are stored in the memory 19 of the winding station computer 14. Before the initiation of a braking procedure, the winding station computer 14 can therefore enquire/ in a simple manner, in which range the thermal load is located at a particular moment, and then specify the braking current with the appropriate strength. -9-WE CLAIM 1. A process for shutting down an electrical drive motor, in particular a drive motor for driving a cam cylinder of a winding station of a bobbin winding machine, which is subjected to a braking current in an opposite direction to a rated current by means of a brake circuit, the magnitude of the braking current may be a multiple of the rated current, characterised in that the thermal load of the drive motor at each particular moment is detected, and the magnitude of the braking current is selected as a function of the thermal load of the drive motor. 2. A process as claimed in claim 1, wherein the thermal load of the drive motor at each particular moment is detected from the current imposition of the drive motor over a time. 3. A process as claimed in claim 1 or 2, wherein the stepped values for braking currents are stored, to each of which a range of a thermal load is allocated. 4. A brake circuit for an electrical drive motor, in particular for a drive motor (13) for driving a cam cylinder (10) of a winding station of a bobbin winding machine, which imposes braking current on the drive motor to provide the braking effect, in the opposite direction to the rated current, the magnitude of the braking current may be a multiple of the rated current, -10-characterised in that means (18) for detecting the thermal loading of the drive motor (13) at a particular moment and means (14) for selecting a magnitude of the braking current to be imposed for a braking process are provided for as a function of the determined thermal load. 5. A brake circuit as claimed in claim 4, wherein the means (14) for selecting the magnitude of the bralring current comprises means for allocation of the momentary thermal load delected to thermal load values stored in a memory (19), and means for determining a braking current with a predetermined strength corresponding to the allocated value. 6. A brake circuit as claimed In claim 4 or 5, wherein the values of thermal loads are stored in the form of stepped ranges in the memory, and wherein a strength of the braking current is predetermined for each of the stepped ranges. In a process for shutting down an electrical drive motor, in particular a drive motor for driving a cam cylinder of a winding station of a bobbin winding machine, which is subjected to a braking current in the opposite direction to a rated current in order to achieve the braking effect, provision is made for the momentary thermal load of the drive motor to be assessed and the strength of the braking current selected as a function of this thermal load on the drive motor.

Documents:

00656-cal-1999 abstract.pdf

00656-cal-1999 claims.pdf

00656-cal-1999 correspondence.pdf

00656-cal-1999 description(complete).pdf

00656-cal-1999 drawings.pdf

00656-cal-1999 form-1.pdf

00656-cal-1999 form-18.pdf

00656-cal-1999 form-2.pdf

00656-cal-1999 form-26.pdf

00656-cal-1999 form-3.pdf

00656-cal-1999 form-5.pdf

00656-cal-1999 letters patent.pdf

00656-cal-1999 priority document others.pdf

00656-cal-1999 priority document.pdf

00656-cal-1999 reply f.e.r.pdf