It is known that, in dobby weaving looms, the elements in- tended to and responsible for the formation of a certain pat- tern on the cloth-that is, the way in which the weft yarns weaves the warp yarns, giving the cloth a particular pattern- are the heald frames, i. e. rigid rectangular structures which are perpendicularly crossed by the warp yarns. The latter ones have two positions (called high frame and low frame in the art slang), and the heald frame function is that of displacing the warp yarns in either position according to the requirements of the pattern set for the cloth being woven. Since for each loom stroke, a certain number of frames will be in the high-frame position and the remaining ones in the low-frame position, downstream of the frames a certain opening of the warp yarns is provided each time, the so-called warp shed, wherein the weft yarn is made to pass through. This operation is followed by closure of the warp yarns by a successive frame displacement retaining the weft yarn and thereby creating a portion of cloth.

Having said that, it is easy to guess that, if a frame does not move correctly, a serious defect is generated in the cloth being woven, which seriously affects the quality of the produced cloth.

It therefore appears to be paramount to carry out a check of the heald frame displacement in weaving looms-as for exam- ple happens in the case of warp and weft yarns-thereby guar- anteeing overall product quality.

The present invention indeed concerns an electronic system which performs such check, which has never been carried out be- fore, thereby filling an important gap in cloth quality checks.

According to the invention, this electronic control system is characterised in that it essentially comprises: an input unit reading the information pertaining to the programmed heald

frame displacements; a transducer assembly detecting the infor- mation-in form of electric signals-pertaining to the heald frame displacements actually occurred; a processing unit per- forming-for each single loom stroke-a comparison between said pieces of information; and stopping means to bring loop operation to rest as soon as said comparison detects weave faults.

In said electronic control system, displacement of heald frames is detected, directly or at the corresponding dobby lev- ers, by using permanent magnets associated with said moving elements and corresponding Hall-effect sensors forming part of a fixed electronic device, to check the position or the dis- placement direction of said moving element.

The electronic control system further comprises: a condi- tioning unit for conditioning said electric signals supplying information both on the programmed and performed displacements; a synchronisation unit associated with the conditioning unit ; and a setting unit for setting acceptance parameters, according to which said processing unit recognises the acceptable error level.

The invention also relates to an electronic device embody- ing the electronic system defined above, which device can be installed both inside the dobby and in the proximity of the heald frames, given that any heald frame displacement is deter- mined by displacement of a corresponding dobby lever.

The invention will now be described in greater detail in the following, with reference to the accompanying drawings, wherein: fig. 1 shows a synthetic representation of a currently preferred embodiment; and fig. 2 shows an easily feasible block diagram.

Synthetically, a FQS electronic system (fig. 1) according to the invention, electrically connected to the weaving loom board QT and to the dobby R, as diagrammatically shown in fig.

1, comprises an input unit reading the information relative to the programmed displacement of the heald frames Q, which dis- placements must be provided by the dobby R, and a transducer assembly detecting the heald frame displacement actually oc-

curred. By carrying out a comparison between the actual posi- tion of the heald frames Q or of the levers L of the dobby R controlling said frames against the programmed displacement im- parted by the loom board QT, the desired check is determined stroke by stroke. Should the system detect a weave (pattern) fault, it immediately stops the loom, halting cloth production.

It is thereby possible to correct the fault.

The system is capable of operating with any heald frame configuration within the range from 0 to 20 heald frames, keep- ing a 12-mm pitch between said frames. The electric power sup- ply is taken from the loom, for example with a supply voltage ranging from 5 to 33V. The loom halt can be controlled through the CAN bus protocol, implementing a dedicated halt message, wherewith a controlled loom halt is associated. Alternatively, a stop signal of exactly the same type as that used in warp stop motion devices can be generated.

Fig. 2 shows a block diagram of the circuit according to which the system has been developed. In the input unit A read- ing of the pattern to be performed occurs, i. e this unit reads from the loom board QT the information relative to the pro- grammed displacement of the heald frames Q. To this purpose in- put unit A is parallel connected to the communication signals line from the loom to the dobby.

The operation can be performed by parallel connecting unit A to the CAN communication bus between dobby and loom and read- ing the"pattern"and"pick counter"messages. Three connection cables are provided between the dobby board and the system ac- cording to the invention, called CANE, CANAL and CANgnd.

As seen, the information on the displacements imparted by the loom is to be compared with that on the displacements actu- ally performed by the dobby machine, for the purpose of estab- lishing the correctness thereof, i. e. of being able to verify the correctness of the pattern on the manufactured cloth. For such purpose, it is essential to read the displacement of the heald frames Q or of the levers L of the dobby R. This reading process is carried out in detecting unit B by using permanent magnets (made of ferrite or NdFeBr) each associated with the surface of a moving element (lever or frame) and of correspond-

ing Hall-effect sensors being part of the printed circuit of the device embodying the system according to the invention. The arrangement of the Hall-effect sensors (transducers) keeps the above said 12-mm pitch, i. e. the pitch of the heald frames or of the dobby levers. Power supply for the Hall-effect sensors is generated by supply unit I (see later), at a 5V set voltage with a peak of 25-30mA of current for each transducer, in an open collector arrangement. Sensor number varies according to the frames to be controlled, up to 20 at maximum.

Alternatively, a pair of Hall-effect sensors can be used for each heald frame of the loom or for each dobby lever to be controlled. Thereby, remarkable advantages can be obtained (with a very moderate cost increase), when the system is in- stalled in weaving loom areas wherein the actual position of the moving elements can be established according to the de- tected direction of movement of the same elements.

In this configuration using a double Hall-effect sensor, the magnet is in fact positioned approximately halfway of the travel of the moving element chosen for the check, so that, due to the substantially symmetrical arrangement thereof, no me- chanical adjustment is required. By adopting this alternative, the system does not detect the high-frame or low-frame posi- tion, but rather the direction in which they are moving, thanks to the activation sequence of the two sensors.

When the system according to the invention is used in a loom already provided with electric signals discriminating dobby angle around 180°-typically obtained by placing one or two proximity sensors inside the dobby-it is favourably pos- sible to take a copy of the above mentioned electric signals and to connect them to the system. This occurs in synchronisa- tion. unit C, for the purpose of obtaining a trigger signal which synchronises the comparison operations between the pro- grammed pattern and the pattern actually performed. The 180° dobby angle corresponds to the angular condition wherein the dobby levers and the heald frames are in their final position and temporarily stationary. The FQS system according to the in- vention is capable of receiving the connection of two synchro- nisation inputs as described above, characterised by a power

signal which can vary from 0 to 30V, with a required current of 5 mA per channel.

The system further comprises a quality level function which can be set by the user storing acceptance parameters, i. e. a certain maximum number of errors within a preset number of strokes, in a setting unit D. The storing process can simply occur, for example, via a programming button provided on the printed circuit, which is directly connected to the processing unit F (see later).

In order to be able to enter the data concerning the ac- ceptance parameters, in the preferred embodiment, it is simply necessary to maintain depressed the above said button for over 2 seconds, and the processing unit F recognises this as a set- ting request and sets itself in programming mode. At this point it is possible to enter the data concerning the fault accep- tance parameter, i. e. the maximum number of errors which will be allowed, ranging from 0 to 99, by briefly pushing down the button for unitary increase of the figure and checking the ac- tual set number on a related display provided in the electronic device of the invention. Upon reaching the desired value, it is sufficient to keep the button down again for over 2 seconds for the set figure to be stored. At the end of this operation the value shown on the display is cleared so that it is possible to enter, similarly to the previous operation, a figure concerning the stroke acceptance parameter, i. e. the number of strokes (ranging from 0 to 990.000, with a pitch of 10.000 strokes) during which the number of occurred errors will be summed up.

At this point the display is finally cleared and will then be increased only in case of a fault, showing instant by instant the total number of faults in the set range of strokes. Upon reaching the set number of strokes, the display is cleared and the fault count starts again from 0. The FQS system stops the loom after a number of faults equal to half the set value, in order to be sure to have, in any range of strokes having the pre-selected number of strokes, a maximum number of faults equal to the entered piece of data.

In order to enable the microcontroller structure found in the programming unit F of the FQS system according to the in-

vention to interpret the input signals, it is necessary to con- dition in advance the input signals. For this conditioning, a specific conditioning unit E of the circuit is provided. Condi- tioning unit E takes into consideration the read signals coming from the CAN communication bus (unit A), the signals generated by the Hall-effect sensors of detecting unit B and the synchro- nisation signals issued by unit C.

The three CAN signals enter the circuit of the FQS system through a transmitter-receiver capable of recognising the elec- tric levels of the CAN bus and of translating them into a sig- nal which may be interpreted by a CAN controller integrated in the microcontroller structure. In order to insulate the CAN circuits of the FQS system, a pair of optical insulators is further arranged between the CAN controller and the transmit- ter-receiver. That enables to power the circuit section dedi- cated to CAN communication separately from the rest of the cir- cuit.

Conditioning of the signals coming from the Hall-effect sensors is simply obtained by means of a pull up resistance for each one of the sensors used. This is because the sensor is a Hall switch, i. e. it only gives an indication on the presence or absence of a magnetic field in the proximity of the active surface of the sensor, bringing the integrated transistor to saturation. Considering that the Hall-effect sensor is in an open collector arrangement, it is necessary to connect a resis- tance between its output and the power supply and to carry the output signal to the microcontroller input.

Finally, as far as synchronisation signals are concerned, in order to be able to accept signals with a voltage excursion of up to 30V, a voltage divider is provided on the input signal through a potentiometer, which, when suitably set, generates the correct voltage to be applied to the microcontroller. A di- ode placed between the voltage divider exit and the power sup- ply protects the processing unit input, and a capacitance to earth filters high-frequency noises.

Processing of input data to generate output data occurs in processing unit F, which represents the core of the device of the FQS system. Such processing is performed by a microcontrol-

ler which has the following features: - non-volatile integrated memory (Flach) larger than 8 Kbyte; - volatile integrated memory (RAM) larger than 1 Kbyte; - integrated EEPROM memory (a few hundred bytes); - over 30 pins available for input/output functions; - integrated CAN controller; - internal PLL; - 5V supply and possibility of accepting signals with a voltage excursion of 5V; - internal"clock"greater than 4MHz.

The microcomputer communicates with all the units de- scribed in fig. 2, and the software residing in the memory thereof is responsible for correct system operation.

The functions performed by the processing unit E are the following: - to verify, upon start of the system, the condition of the line connected to the programming button and, in case the latter is kept depressed for a pre-established time, to enable the procedure for setting the accep- tance parameters (please refer to the description of setting unit D); - to read via CAN bus the"pick counter"and"dobby pat- tern"messages, so as to create a buffer of data relat- ing to the displacements which are to be performed by the loom; - to read the condition of the Hall-effect sensors and form a bit vector (up to 20), within which the state (0-1) of each of them mirrors the position (low- frame/high-frame) of the associated heald ; - to compare the input data at each stroke in a way syn- chronous with an external signal or, should it not be possible to obtain such synchronisation signal, by choosing a particular message of the CAN bus as a syn- chronisation signal (as described below); - to increase, in case of a fault, the total number of faults, to compare the value thereof with the fault ac- ceptance parameter and if necessary to stop the loom;

- to sum up the total number of performed strokes and to reset the counter should such value reach the limit set by the stroke acceptance parameter; - to manage the signals which are useful for displaying data on the displays showing fault and set up values of the acceptance parameter.

In the impossibility to connect one or two synchronisation signals to the system device, the system will have to manage the pattern control function automatically. In this case, the "pick counter"CAN message will be adopted, as a final deadline for the correct formation of lever displacement.

The data processed in processing unit E should finally be sent to the weaving loom, when an unacceptable error level is detected by said unit, and the loom should consequently be stopped. This task is accomplished by the stopping unit G and can be accomplished in two different ways.

The first one is similar to the connection of"loom stop" of the warp stop motion devices, i. e. through saturation o a npn transistor, controlled by an output line of the microcon- troller. The"loom stop"is brought to the low logic level. As well as stopping the loom through saturation of this transis- tor, it causes a red LED diode to light up.

The second way to stop the loom uses the CAN bus. A stop message is implemented, wherewith a controlled stop procedure is associated which allows to stop the loom without generating faults in the fabric.

The electronic device embodying the system according to the invention also comprises-as already mentioned-a display unit (unit H). This preferably comprises a pair of 7-common- cathode-segment displays which are employed to manage the com- munication interface with the user. Their function can be summed up in two concepts: - visualising the number of current faults, - programming the acceptance parameters.

The two displays are controlled by a pair of integrated circuits which power with the appropriate current the segments of the displays meant to light up according to the logic level of the 4 lines present at the input thereof.

The electronic board of the system device is preferably <BR> <BR> powered-from supply unit I (refer to fig. 2) -with a direct current in a voltage range from 5V to 33V, typical value 24V dc. The purpose of supply unit I is to produce output voltage adjusted at 5VS, to be distributed to the previously shown com- ponents and units. Performing such function is the task of an integrated switching regulator, which comprises an inductor, a Schottky rectifier diode and an electrolytic condenser. The in- put is protected against voltages exceeding 33V and a pair of electrolytic condensers provides a first filtering action sta- bilising the input voltage. By lighting up, a green LED diode shows the presence of output voltage at the regulator. Further- more, a Zener diode takes over output voltage at 5,6V in case of a fault increasing voltage, thereby preventing the inte- grated circuits connected to the switching from being damaged.