EP0071141A2

EP0071141A2 - Sliver detecting device for dividers of spinning cards

Info

Publication number: EP0071141A2
Application number: EP82106479A
Authority: EP
Inventors: Paolo Bobbola
Original assignee: Roj Electrotex SpA
Current assignee: Roj Electrotex SpA
Priority date: 1981-07-29
Filing date: 1982-07-19
Publication date: 1983-02-09
Also published as: IT8123225A0; IT1138893B; EP0071141A3

Abstract

A device for checking the presence of slivers in carding machines and the like comprises: a number of piezoelectric feeler units equal to the number of slivers to be checked, and on which said slivers are simply rested and slide during their movement, said feeler units converting the mechanical vibrations produced by the movement of the slivers on said units into oscillating electrical signals; a switchable channel fed by said piezoelectric feeler units and conveying to a single output at different moments of time the signals which reach the channel at separate inputs; a single signal amplifier tuned to the frequency range produced by the feeler units; a selection circuit which chooses only one feeler unit at any given moment and connects it to the amplifier; and an actuator circuit which integrates the signal originating from the amplifier and produces a stop signal and_/or activates alarm means if one or more of the signals originating from the feeler units are indicative of a broken or absent sliver.

Description

This invention relates to a device for checking the presence of slivers at the divider outlet of carding machines, and for signalling the absence or breakage of one or more of said slivers.
In spinning, it is particularly important for the soundness of the slivers collected on the cops to be checked at the outlet of the carding machine divider.
This is because a broken sliver can accumulate at the outlet of the rubbing sleeves, thus involving further slivers, with the result that lurching can take place causing serious machine damage.
A known system for detecting the presence of slivers comprises a photoelectric optical barrier. In this case, a modulated light beam travels along each sliver intake path over the whole of its length, in a position which coincides with the falling trajectory of each sliver.
With this type of detection, in many cases the sliver does not interrupt the optical barrier on breaking, so that there is no indication. In these cases the broken sliver is entrained by the adjacent one and is not indicated.
Another known system utilises the resultant falling action of a lever supported by the sliver.
As the lever is electrically isolated from earth and is kept distant from a common earthing surface by the sliver, the isolated lever has to be preloaded with a certain tension and given a secure path of travel in order to ensure its proper operation.
These conditions however give rise to greater stressing of the sliver, which is undesirable. In addition, proper operation depends upon the state of contact, which itself is dependent on the external agents which tend to deteriorate it.
The object of the invention is to provide a device for checking and indicating sliver breakage which is able to monitor the movement of the slivers in their direction of movement, independently of their tension, by means of detection members which emit electrical signals when in contact with said slivers.
A further object of the invention is to provide a simple circuit configuration for such a device which avoids the need to use a separate amplifier for each of said detection members in order to amplify the electrical signals emitted thereby.
The checking and indicating device according to the invention is essentially characterised by comprising: a number of piezoelectric feeler units equal to the number of slivers to be checked, and on which said slivers are simply rested and slide during their movement, said feeler units converting the mechanical vibrations produced by the movement of the slivers on said units into oscillating electrical signals; a switchable channel fed by said piezoelectric feeler units and conveying to a single output at different moments of time the signals which reach the channel at separate inputs; a single signal amplifier tuned to the frequency range produced by the feeler units; a selection circuit which chooses only one feeler unit at any given moment and connects it to the amplifier; and an actuator circuit which integrates the signal originating from the amplifier and produces a stop signal and/or activates alarm means if one or more of the signals originating from the feeler units are indicative of a broken or absent sliver.
Each feeler unit of this device comprises a suitably shaped and treated metal member on which the sliver rests and runs, and to which a piezoelectric ceramic member is rigidly fixed.
A preferred embodiment of the invention is described hereinafter in greater detail with reference to the accompanying drawings, in which:

Figure 1 is an overall external view of a feeler unit of the device according to the invention;
Figure 2 is a section through the feeler unit of Figure 1;
Figure 3 is a block diagram of the electronic circuit of the device;
Figure 4 shows the wave forms of the main signals generated in the circuit of Figure 3;
Figure 5 is a diagram of the actuator circuit of the electronic circuit of Figure 3;
Figure 6 shows the wave forms of the signals which appear in the circuit of Figure 5;
Figure 7 is an alternative diagram of the actuator circuit of the device;
Figure 8 shows the wave forms of the signals which appear in the circuit of Figure 7;
Figure 9 represents one embodiment of the switchable channel of the circuit of Figure 3; and
Figures 10 and 11 represent two modified embodiments of the switchable channel of the circuit of Figure 3.

The device according to the invention comprises a number of piezoelectric feeler units T such as those shown in Figures 1 and 2 equal to the number of slivers to be checked. Each of these units, which are designed to convert the mechanical vibrations due to the sliver movement into an oscillating electrical signal, comprises a feeler element 1 constituted by a metal member in the shape of a curved plate on which the sliver S simply rests and slides as it leaves the carding machine divider. The outer surface of the member 1 on which the sliver slides is treated to produce very low friction and maximum resistance to wear by rubbing. A piezoelectric ceramic bush 2 is cemented to the metal member 1 and is disposed in a position such as to provide the maximum electrical signal/sliding transformation ratio.
The feeler unit is connected to the electronic circuit by conductors 3 and 4. The conductor 3 connected to the piezoxide carries the electrical signal, while the conductor 4 connects the feeler member to earth, to prevent accumulation of electrostatic charges on the feeler unit.
A number of feeler units are generally enclosed in a suitable container and disposed at a fixed distance apart to constitute a detector module. Each detector module is connected to the electronic circuit by a screened cable comprising n + 1 conductors, where n is the number of units constituting the module. It has been found convenient for each module to comprise twelve units. Several modules are connected to the same electronic circuit.
A preferred configuration of the invention comprises four modules of twelve units each, which are connected to the same electronic control circuit. The number of possible combinations is however obviously very great.
With reference to the diagram of Figure 3, it can be seen that the signals Rl, R2... Rn generated at the output of the feeler units Tl, T2.... Tn are presented to the amplifier A at different moments by means of a switchable channel CC.
In this respect, inside the channel CC, which can be formed in various ways, the signals emitted by said units are selected by electronic switches Il, I2, ... In controlled by a selection circuit CS, such that only one signal at a time, namely that originating from the selected detection unit, is present at the input of the amplifier A at any given moment.
The output signals UA from the amplifier A are fed to an actuator circuit CA, to which the synchronisation signals SS are also fed by the selection circuit.
The actuator circuit CA is shown in greater detail in Figure 5, again in the form of a block diagram. This is a constant integration circuit in which the signal UA fed by the amplifier A is filtered by the integrator I in accordance with a suitable time constant such as not to be influenced by the sliver fluctuations on the feeler movement, and is then fed to a memory Ml. The actuator circuit CA also comprises a second memory M2 arranged to emit signals ALT for halting the machine being monitored, and for activating alarm means AL and a warning lamp L. The memory M2 is fed both by the signals SR from the first memory M1 and by signals R which, by way of a pulse counter n, reach a gate P which is also fed by both the synchronisation signals SS and the halt signals produced by said memory M2.
The signal present at the output of the amplifier A is indicated by UA. It can be seen that when sliding over one of the detection units ceases, the signal at the output of the amplifier A does not cease until the corresponding unit is connected to it by the channel CC by means of the corresponding selection signal.
The ALT signal is provided to correspond with the corresponding synchronisation signal SS.
The time period Tl which determines the selection rate of the inputs and thus of the system is fixed in accordance with the time constant chosen for the integrator I of the circuit CA.
The response speed is given by n x Tl, where n is the number of connected detection units and Tl the time necessary for checking whether sliver sliding is occurring on each detection unit.
If the sliver on the i detection unit breaks, the memory M1 supplies the signal SR. This signal is memorised by the memory M2, which causes the lamp L to light.
The ALT signal thus generated opens the gate P, which allows the synchronisation pulses to pass, these then being counted. The signal R is generated when the i^th detection unit is again selected. The signal R deactivates the memory M2 which is however immediately reactivated by SR if the i^th sliver has not yet been made good, and the cycle continues in this manner until said sliver has been made good.
Figure 7 shows a further embodiment of the actuator circuit CA which gives greater response speed of the system.
It comprises two integrators, a fast integrator Il and a slow integrator I2 in place of the single integrator I, and two memories Ml and M2, two gates Pl and P2, and a pulse counter m.
The signal UA originating from the amplifier A is integrated by the fast integrator Il in accordance with a time constant lower than that'used in the previously described embodiment of Figure 5.
When a signal is present at the output of Il which indicates a defect in the sliding of the sliver, Ml generates a signal AR which requests a stoppage, this signal blocking the selection circuit CS of the device at the feeler unit which has just been selected. In this manner, the signal UA is integrated by the slow integrator 12 in accordance with the suitable time constant, and is read by the memory 1-2 which generates the ALT signal in the case of breakage of the sliver.
In this manner, the response time of the system is less than in the case using the actuator circuit of Figure 4, because the selection time of each unit is less than the time used in deciding whether a sliver breakage has occurred.
Figure 9 shows the operational diagram of the switchable channel CC of Figure 3 in a preferred embodiment.
Each detection unit Tl, T2 ... Tn is connected to the analogue adder SA constituted by an operational amplifier with feedback in said configuration.
The controlled switches ICT1, ICT2 ... ICTn either short- circuit the signal originating from their own branch or allow it to pass, according to the control signal which they receive.
In this case, the selection circuit is constructed in such a manner that only one switch is open at any given moment, and all the others are closed. By this means, the signal originating from only one detection unit passes to the amplifier by way of the band pass filter F (disposed at the adder output to reduce noise).
The other switchable channel embodiments shown in Figures 10 and 11 are modifications of this latter circuit, and require no particular explanation for the expert of the art.
It should merely be noted that in the embodiment of Figure 10, the switchable channel is constituted by the set of feeler units Tl, T2 ... Tn, to each of which a controlled electronic switch is connected in parallel. At any given moment only one of these switches is selected into the open position by the selection circuit CS, all others being closed. In the embodiment of Figure 11, the switchable channel is constituted by an analogue adder having a number of inputs equal to the number of feeler units Tl, T2 ... Tn. Each of these units is connected by a corresponding controlled electronic switch ICT1, ICT2 ... ICTn, which can be selected into the open or closed position by the selection circuit CS.
At any given moment only one of these switches can be selected into the closed position in order to feed the amplifier A with the signal originating from the corresponding feeler unit.
The invention also covers other embodiments different from those described and illustrated provided they fall within the scope of the inventive idea. For example, instead of using - to amplify signals from piezoelectric feeler units-a sole amplifier combined with a switchable channel and with a selection circuit, an amplifier and an actuator for each feeler unit would be used.

Claims

1) A device for checking the presence of slivers at the divider outlet of carding machines, charcterized by comprising: a number of piezoelectric feeler units equal to the number of slivers to be checked and on which said slivers are simply rested and slide during their movement, said feeler units converting the mechanical vibrations produced by the movement of the slivers on said units into oscillating electrical signals; means for amplifying said signals; and at least an actuator circuit fed with the output of said amplifying means, which actuator circuit produces a stop signal and/or activates alarm means if one or more signals from feeler units are indicative of a broken or absent sliver.

2) A device as in claim 1) in which said means for amplifying the oscillating electrical signals from feeler units comprise a switchable channel fed by said piezoelectric feeler units and conveying to a single output at different moments of time the signals which reach the channel at separate inputs; a single signal amplifier tuned to the frequency range produced by the feeler units and a selection circuit which selects only one feeler unit at any given moment and connects it to the amplifier; and in which a sole actuator circuit integrates the signal originating from the amplifier and produces a stop signal and/or activates alarm means if one or more signals originating from the feeler units and indicative of a broken or absent sliver.

3) A device as in claims 1) and 2), wherein each feeler unit comprises a suitably shaped and treated metal member on which the sliver rests and slides, and to which a piezoelectric ceramic member is rigidly fixed.

4) A device as in claim 3), wherein said metal member of the feeler units is connected to earth in order to prevent accumulation of electrostatic charges.

5) A device as in claim 2), wherein the switchable channel is constituted by an analogue adder having a number of inputs equal to the number of feeler units, at any given moment controlled electronic switches short-circuiting to earth the signal originating from all feeler units with the exception of the one connected to that input which at that determined moment is caused by the selection circuit to transmit the signal to the amplifier, the various feeler units being connected in a predetermined succession by the selection circuit.

6) A device as in claim 2), wherein the switchable channel is constituted by the set of feeler units, to each of which a controlled electronic switch is connected in parallel, at any given moment only one switch being selected into the open position by the selection circuit, the others being closed, the selection circuit causing each selection switch to open at different moments.

7) A device as in claim 2), wherein the switchable channel is constituted by an analogue adder having a number of inputs equal to the number of feeler units, each unit being connected to its own input by a controlled electronic switch which can be selected into the open or closed position by the selection circuit, at any given moment only one switch being selected into the closed position to allow the signal originating from the selected unit to reach the amplifier.