EP0962570A2

EP0962570A2 - Method for checking the selection of the needles of a needle cylinder in knitting machines particularly for hosiery and the like

Info

Publication number: EP0962570A2
Application number: EP99109276A
Authority: EP
Inventors: Francesco Lonati; Tiberio Lonati; Ettore Lonati; Fausto Lonati
Original assignee: Macchine Tessili Circolari MATEC SpA
Current assignee: Macchine Tessili Circolari MATEC SpA
Priority date: 1998-06-03
Filing date: 1999-05-27
Publication date: 1999-12-08
Also published as: EP0962570A3; ITMI981228A1

Abstract

A method for checking the selection of the needles of a needle cylinder in knitting machines particularly for hosiery and the like comprising a needle cylinder (1) on the cylindrical surface of which a plurality of axial slots (2) are provided, each of which accommodates a needle (13) and at least one selection element, selectors constituted by permanent magnets and coils which laterally face the needle cylinder (1) at the level of the selection elements and selection (3) and sensor (4) means, the particularity of the method consisting in that it comprises the steps of:

determining the relative position of the selection means (3) and of sensor means (4) located alternately with respect to the selection means (3), so as to determine the number of selection elements present between the position of the selection means (3) and the position of the sensor means (4);

detecting, through the sensor means (4), the transit of the selection elements selected by the selection means (3);

sampling the signals acquired by the sensor means and comparing the sampled signals acquired by the sensor means (4) with the corresponding control signals sent to the selection means (3) in order to check the correct selection of the selection elements.

Description

The present invention relates to a method for checking the selection of the needles of a needle cylinder in knitting machines, particularly for hosiery and the like.
It is known that knitting machines for hosiery and the like provided with a needle cylinder on the lateral surface of which a plurality of slots are provided, each of which accommodates a needle and a corresponding needle selection element, also have selection means which are constituted for example by a permanent magnet and by a coil which is supplied with an appropriate current.
The permanent magnet of the selection means allows to attract the selection element and therefore to control the actuation of the corresponding needle, i.e., its upward motion or its retention in the inactive condition when it must not be selected.
The selection means are arranged laterally with respect to the needle cylinder at the needle selection elements.
The solutions that are currently used accordingly provide for the automatic selection of the needles by way of the selection means and the selection elements, but they do not allow to know which needles have been selected in order to check whether the selection programming performed by the user has been executed correctly.
The selection means may in fact fail to operate correctly or the selection elements themselves may be defective.
The aim of the present invention is to provide a method for checking the selection of the needles of a needle cylinder in knitting machines for hosiery and the like.
Within the scope of this aim, an object of the present invention is to provide a method for checking the selection of the needles of the needle cylinder in knitting machines, particularly for hosiery and the like, in which it is possible to check the correct operation of the selection means and/or of the selection elements.
A further object of the present invention is to provide a method for checking the selection of the needles of the needle cylinder in knitting machines particularly for hosiery and the like, in which the selection of one group of needles can be checked during the selection of other needles.
A further object of the present invention is to provide a method for checking the selection of the needles of a needle cylinder in knitting machines particularly for hosiery and the like, which constitutes a diagnostic function for said machines.
A further object of the present invention is to provide a method for checking the selection of the needles of a needle cylinder in knitting machines particularly for hosiery and the like, which is highly reliable, relatively easy to provide and at low costs.
This aim, these objects and others which will become apparent hereinafter are achieved by a method for checking the selection of the needles of a needle cylinder in knitting machines particularly for hosiery and the like comprising a needle cylinder on the cylindrical surface of which a plurality of axial slots are provided, each of which accommodates a needle and at least one selection element, and selectors constituted by permanent magnets and coils which laterally face the needle cylinder at the level of the selection elements, characterized in that it comprises the steps of:
determining the relative position of said selection means and of sensor means located alternately with respect to said selection means, so as to determine the number of selection elements present between the position of said selection means and the position of said sensor means;
detecting, through said sensor means, the transit of said selection elements selected by said selection means;
sampling the signals acquired by said sensor means and comparing said sampled signals acquired by said sensor means with the corresponding control signals sent to said selection means in order to check the correct selection of said selection elements.
Further characteristics and advantages of the invention will become apparent from the following detailed description of a preferred embodiment of the method according to the invention, illustrated only by way of non-limitative example in the accompanying drawings, wherein:
Figure 1 illustrates schematically the method for checking needle selection according to the present invention; and
Figure 2 is a block diagram which schematically illustrates a loop control provided by means of the method according to the present invention.
With reference to the above Figures, the method for checking needle selection according to the invention is as follows.
First of all, the needle cylinder is designated by the reference numeral 1 and a plurality of slots 2 are provided on its cylindrical surface; each slot accommodates a needle and at least one selection element, both of which are not shown in the Figure. The slots 2 are arranged axially on the cylindrical surface of the needle cylinder 1 and there are selection means, one of which is schematically designated by the reference numeral 3, which are arranged laterally with respect to the cylindrical surface of the cylinder and are designed to drive needle selection by acting on the corresponding selection elements, which can be, for example, pins.
Each selection means comprises a permanent magnet which internally accommodates a coil which is appropriately controlled by a current signal, in order to allow to draw the selection pin or keep it in its inactive position, respectively for selecting or not selecting a corresponding needle.
A plurality of sensor means, fully similar to said selection means, are arranged so as to be alternated between said selection means 3 and are designated by the reference numeral 4 in Figure 1, which illustrates only one sensor means.
Like the selection means 3, the sensor means 4 are arranged laterally with respect to the cylindrical surface of the needle cylinder 1 and at the selection elements.
With reference to Figure 1, the chart shown in the upper portion of the Figure plots current pulses sent to the selection means 3 and the chart in the lower portion of the Figure plots the signals sampled on the sensor means 4.
The peaks of the signal shown in the lower part of Figure 1 have the following correspondence: the negative peak corresponds to the entry of the selection element in the active area of the selection means 3; the positive peak corresponds to the exit of the selection element from the active area.
Accordingly, the portions of the signal constituted by the pair of positive and negative peaks define the selection of a selection element, i.e., its disengagement from the pull of the permanent magnet of the selection means 3 and therefore the selection of the corresponding needle.
The method according to the invention has an initial step during which the angle α between the selection means 3 and the sensor means 4, i.e., the angle that determines the number of selection elements interposed between the selection means 3 and the sensor means 4, is determined. This accordingly gives an indication of the delay with which the sensor means can detect a selection element selected by the selection means 3.
Current pulses sent to the selection means 3 are plotted, as mentioned, in the upper portion of Figure 1; said pulses must correspond to related signals detected by the sensor means 4 and induced by the transit of the selection element in front of said sensor means.
The transit of the selection elements in front of the sensor means 4 causes a current to be induced in the corresponding coils when the selection elements pass at a certain speed in front of the active region of the selection means. This passage in fact causes an alteration in the magnetic balance which in turn induces an electrical signal across the coils.
The signal that arrives from the sensor means 4 is sampled at a rather low frequency, typically eight samples distributed over the space of a needle. During this sampling step, the CPU 10, shown as a block in Figure 2, must select other groups of needles.
Then, once the angle α between the selection means 3 and the sensor means 4 has been measured and the positions of the selection means 3 and of the sensor means 4 with respect to the needle cylinder have therefore been determined, the signals that arrive from the sensor means, sampled appropriately, allow to provide useful information regarding the correct or incorrect operation of the selection means and/or of the selection elements.
The charts of Figure 1 plot the two possible error conditions.
The numerals 1 to 10 arranged at the axis of the abscissae designate the number of the needles at which the measurements are made.
Therefore, by examining the chart related to the signal sampled on the sensor means 4 it can be seen that at the fourth needle there is a failed disengagement, i.e., the selection element was activated by the CPU and the corresponding selection means 3 received the current pulse, but the sensor means 4 did not detect any transit of the selection element in front of them. Therefore, instead of having a portion of signal in which the characteristic waveform that indicates the entry and exit of the selection element into and from the active region of the selection means 3, the waveform of the sampled signal has a flat shape which coincides with the axis of the abscissae and therefore indicates no transit of the corresponding activated selection element.
The second error condition occurs at the needle 6, where an unexpected disengagement of the needle occurs.
By examining the corresponding chart which plots the current pulses sent to the selection means 3, it is in fact noted that the current pulse at the needle number 6 was not sent and that on the contrary the waveform of the signal sampled on the sensor means 4 indicates the transit of the selection element related to the needle 6 in front of the sensor means 4.
Accordingly, an unwanted selection, not activated by the operator, has
occurred. This indicates that evidently the permanent magnet of the selection means 3 was not able to retain the selection element that corresponds to the needle 6.
Therefore, the described method provides the operator with the information required to understand whether the problem is only a defective selection element (and, if so, which selection element) or the selection means 3 are defective, since they are unable to select the selection elements.
With reference now to Figure 2, said Figure illustrates, in the form of a control loop, the above described process.
In practice, the variable that is controlled in the process is the type of selection on each needle: high or low, i.e., selected or not selected. The microprocessor (CPU) 10 processes a programmed selection configuration for each needle, designated by the block 11, and accordingly generates the pulses 12 to be sent to the selection means 3 to actuate the corresponding needles, designated by the reference numeral 13.
The sensor means 4 then detect the state assumed by each needle.
The system can be considered as an open-loop system: although the sensor means 4 can check the outcome of the actuation by the selection means 3, the system is unable to self-adjust and can merely report any selection errors to the operator.
However, if the information that arrives from the sensor means 4 is returned to the CPU 10 by means of a feedback branch 14, the control loop closes and one obtains an automatically regulated system.
The CPU 10 in fact has all the mechanisms and signals for identifying the optimum parameters of the pulses independently, without any intervention on the part of the operator.
It is therefore possible to have in this case on board the knitting machine for hosiery and the like a special function, to be used during the installation of the machine, after performing a process for self-learning the position of the different selection means 3 with respect to the selection elements accommodated in the slots of the cylindrical surface of the needle cylinder 1.
The self-learning of the position of the selection means is the subject of a co-pending patent application in the name of the same Applicant as the preceding application and is assumed included herein by reference.
Accordingly, when the machine is being installed it is necessary to generate a test configuration on one or more selection means in sequence, checking the outcome of the selection on the corresponding sensor means. On the basis of this information, the parameters of the electrical pulse designed to control the selection elements through the coils of the selection means can be changed at will by the microprocessor 10.
Said parameters are, for example, shape, amplitude, duration and position.
As a consequence of the execution of the above described method, the optimum parameters, i.e., the parameters centered in the operating range, are determined automatically; said parameters might even be different for each one of the selection means 3.
In practice it has been observed that the method according to the invention fully achieves the intended aim and objects, since it allows to check the selection of the needles of a needle cylinder and to provide the operator with information on the correct operation of the selection elements and of the selection means.
The method thus conceived is susceptible of numerous modifications and variations, all of which are within the scope of the inventive concept; all the details may further be replaced with other technically equivalent elements.
The disclosures in Italian Patent Application No. MI98A001228 from which this application claims priority are incorporated herein by reference.
Where technical features mentioned in any claim are followed by reference signs, those reference signs have been included for the sole purpose of increasing the intelligibility of the claims and accordingly, such reference signs do not have any limiting effect on the interpretation of each element identified by way of example by such reference signs.

Claims

A method for checking the selection of the needles of a needle cylinder in knitting machines particularly for hosiery and the like comprising a needle cylinder (1) on the cylindrical surface of which a plurality of axial slots (2) are provided, each of which accommodates a needle and at least one selection element, selectors constituted by permanent magnets and coils which laterally face the needle cylinder (1) at the level of the selection elements and selection (3) and sensor (4) means, characterized in that it comprises the steps of:

determining the relative position of said selection means (3) and of sensor means (4) located alternately with respect to said selection means (3), so as to determine the number of selection elements present between the position of said selection means (3) and the position of said sensor means (4);

detecting, through said sensor means (4), the transit of said selection elements selected by said selection means (3);

sampling the signals acquired by said sensor means (4) and comparing said sampled signals acquired by said sensor means (4) with the corresponding control signals sent to said selection means (3) in order to check the correct selection of said selection elements.
The method according to claim 1, characterized in that the step that consists in sampling said signals arriving from said sensor means (4) provides for the sampling of said signals at a low frequency.
The method according to claim 1, characterized in that it comprises a step for feeding back (14) said sampled signals that arrive from said sensor means to a central processing unit (10) which is adapted to send said control signals to said selection means (3).
The method according to one or more of the preceding claims, characterized in that it comprises a step for defining a selection which is programmed needle by needle in order to send said selection to said central processing unit (10).
The method according to one or more of the preceding claims, characterized in that said processing unit (10) is adapted to modify, on the basis of said feedback signal (14), the parameters of said control signals sent to said selection means (3).
A device for checking the selection of the needles of a needle cylinder in knitting machines for hosiery and the like which comprise a needle cylinder (1) on the cylindrical surface of which a plurality of axial slots (2) are provided, each of which accommodates a needle (13) and at least one selection element, selection means (3) being provided which face said cylindrical surface laterally at said at least one selection element, characterized in that it comprises sensor means (4) which are arranged so as to be spaced with respect to said selection means (3) and are adapted to detect signals which indicate the transit of each one of said selection elements in front of them as a consequence of the rotation of said needle cylinder (1), said detected signals being correlatable to signals for controlling said selection elements in order to check the compliance of said selection elements with the respective control signals.
The device according to claim 6, characterized in that it comprises a central processing unit (10) which is adapted to store a programmed configuration for selecting said needles (13) and to correspondingly control said needles by way of said control signals through said selection means (3).
The device according to claim 7, characterized in that said sensor means (4) feed back (14) said detected signals to said central processing unit (10) in order to adjust the parameters of said control signals sent by said central processing unit to the selection means (3).
The device according to claim 7, characterized in that said sensor means (4) are identical to said selection means (3) and are arranged in the same position as said selection means (3) with respect to said needle cylinder (1).