EP0184779A2

EP0184779A2 - Device for restoring a loom to predetermined operative conditions to resume working after an interruption, particularly after breakage of the weft

Info

Publication number: EP0184779A2
Application number: EP85115492A
Authority: EP
Inventors: Dore Dondi Benelli
Original assignee: Ergotron Sas Di Dondi Benelli Dore & C
Current assignee: Ergotron Sas Di Dondi Benelli Dore & C
Priority date: 1984-12-10
Filing date: 1985-12-05
Publication date: 1986-06-18
Anticipated expiration: 2005-12-05
Also published as: ATE55426T1; DE3579127D1; IT8468228A1; IT8468228A0; EP0184779B1; EP0184779A3; IT1179857B

Abstract

The device comprises:

- detector means (30; 34, 35; 50) for providing electrical signals indicative of the length of warp (3) unwound at each beating-up in normal operation of the loom,
- memory means (52) connected to the detector means for storing signals indicative of the warp length unwound at each beating-up,
- drive means (20, 21) for causing rewinding of the warp (3) on the warp beam (2), and
- control and operating circuit means (40) connected to the detector means (30; 34, 35; 50), to the memory means (52) and to the drive means (20) and arranged after an interruption of the operation of the loom, particularly due to breakage of a weft thread, to actuate the drive means (20) to cause rewinding of the warp (3) and a corresponding drawing back of the textile (T) to an extent which is in a predetermined ratio to the last value of warp length stored in the memory means (52) before the interruption.

Description

The present invention relates to a device for restoring a loom to predetermined working conditions to resume its operation after an interruption, particularly after a weft breakage.
Every time the operation of a loom is stopped. particularly following breakage or exhaustion of the weft, the sley may, due to inertia, effect one or more empty beats, and the textile controller continues to wind the woven textile. The loom having been stopped and the weft renewed, if the loom is started again with the textile and the warp in the same conditions in which the operation was effectively interrupted, defects known as weft "barres", in particular voids, are created in the textile, since several weft threads are missing at the point of restarting. These defects are the consequence of the empty beats effected by the sley before the effective stoppage of the loom, after the occurrence which had caused the interruption in operation. These defects may be even more marked when the thread used in the weaving is of a type almost free from elasticity and prone to extensive yielding. In this case a stoppage of the loom even if only for a short period may cause elongation of the woven textile as well as in the chain, with consequent displacement of the beat-up line of the weft on restarting. A further cause of defects in the woven textile upon resumption of weaving is that the first beat upon restarting is effected under conditions which are generally different from those during normal operation and in particular the sley arrives at the beat-up line with an accelerated movement, starting from rest.
The object of the present invention is to provide a device which allows the restoration of a loom to predetermined working conditions upon resumption of its operation after an interruption, particularly after a breakage or exhaustion of the weft, so as to avoid the formation of weft barres in the woven textile upon resumption of working.
This object is achieved according to the invention by means of a device, the main characteristics of which lie in that fact that it includes

- detector means for providing electrical signals indicative of the length of warp unwound at each beating-up in normal operation of the loom,
- memory means connected to the detector means for storing signals indicative of the warp length unwound at each beating-up,
- drive means for causing rewinding of the warp on the warp beam, and
- control and operating circuit means connected to the detector means, to the memory means and to the drive means and arranged after an interruption in the working of the loom to actuate the drive means to cause rewinding of the warp, and corresponding drawing back of the woven textile, to an extent which is in a predetermined ratio to the last value of the warp length stored in the memory means before the interruption.

According to a further characteristic, the device according to the invention further includes processing circuit means connected between the detector means and the memory means and arranged to determine cyclically the average value of the warp length unwound at each beating-up from a predetermined number of beatings-up, and to supply electrical signals indicative of this average value to the memory means.
The said control and operating circuit means in general are arranged to cause rewinding of the warp to an extent corresponding to a whole multiple on the average value.
Preferably the control and operating circuit means are arranged to cause rewinding of the warp to an extent corresponding to a whole multiple plus a predetermined fraction of the average value.
For looms having warp tension adjustment devices including an electric motor for driving the beam, the device according to the invention is characterised in that the said drive means are constituted by the same electric motor as that of the warp tension adjustment device.
This warp tension adjustment device is conveniently constituted by the patented device made and sold by the Applicant under the trade name "TENDILENE".
Further characteristics and advantages of the device according to the invention will become apparent from the detailed description which follows, given with reference to the appended drawings, provided purely by way of non-limiting example, in which:

Figure 1 is a schematic illustration of a loom provided with a device according to the invention, and
Figure 2 is a circuit diagram partially in block form of one embodiment of the device according to the invention.

In Figure 1 of the appended drawings a loom is illustrated schematically, including a support frame 1 carrying a beam 2 at one end on which the warp threads or chain 3 are wound. These threads pass over a deflector roller (back rest) 4 supported in a fixed position by the frame 1. A further movable tensioning roller 5 is carried by first arms 6a of inter-pivoted, V-shaped levers 6 (of which only one is.visible in Figure 1), articulated on the frame by means of pivot pins 7. Springs 8 are connected to the second arms 6b of the levers 6 and are anchored to the loom frame so as to bias the thread-carrying roller 5 upwardly.
After leaving the warp beam 2, the warp chain threads 3 are deflected over the roller 4 and then tensioned by the roller 5 as a result of the action of the springs 8.
The warp chain threads 3 then reach a series of heddles 9 which separate them into two groups defining the warp opening or shed 10 in which the weft threads are inserted in succession in operation.
A sley is indicated 11 which, after the insertion of a weft, beats-up the weft to form the woven textile T, usually with an angular motion. The textile piece is then wound onto a beam 12 by a piece drawing roller 13.
The beam 12 and the piece drawing roller 13 are both carried by the frame 1.
The main or drive shaft of the loom, from which the sley 11 (inter alia) and the heddles 9 are driven through suitable mechanisms, is indicated 14.
Reference 20 indicates an electric motor fixed to the frame 1 of the loom adjacent the beam 2. This motor is, for example, a single phase induction motor with a starting capacitor. The output shaft 20a of this motor rotates the warp chain beam 2 through a gear transmission system 21. One detailed embodiment of the gear transmission 21 is described in Italian patent application no. 68110-A/82 filed by the same Applicants. This transmission achieves a velocity reduction so that when the electric motor 20 is operated and its shaft rotates at a certain speed, it causes the warp beam 2 to rotate much more slowly.
Preferably, although not necessarily, the electric motor 20 and the transmission 21 form part of a warp regulating device controlled by a warp tension sensor. This regulating device includes, for example, a strap 15 fixed to the arm 6a of a lever 6 as shown in Figure 1 and extending between the two arms of a photoelectric position detector generally indicated 16. This detector is fixed to the loom and, in known manner, has two facing arms in which a light source (or infra-red source) and a photoelectric sensor (for example a photoresistor) are housed respectively. In Figure 2 the light source and the photoresistor are indicated 17 and 18. In operation, the strap 15 cuts off the radiation from the source to the photoresistor to an extent which is variable in dependence upon the tension of the warp threads. The voltage between the ends of the photoresistor varies correspondingly. The photoresistor is connected in a voltage divider connected to the input of a speed regulating circuit 19 of known type for the motor 20. The regulating circuit regulates the speed of the motor in dependence upon the reference voltage supplied to it by the divider including the photoresistor 18, and in dependence upon the speed of the motor itself detected by a sensor S coupled to it.
In the embodiment illustrated in Figure 1, the device according to the invention includes a tachometric sensor 30 coupled to the electric motor 20 for providing a pulsed electrical signal at a frequency indicative of the speed of rotation of the motor and hence the speed of unwinding of the chain 3 from the beam 2. The tachometric sensor 30, which may be constituted by a phonic wheel sensor, could alternatively be coupled to a member of the transmission 21 or to the shaft of the beam 2.
If, as in the embodiment illustrated, the loom has a warp regulating device with an independent electric motor for driving the beam, the tachometric sensor 30 and the speed sensor S of the regulator may be constituted by a single device.
Reference 31 indicates a sensor for detecting the operation of the loom. If the shaft 14 is driven by an electric motor, this sensor could simply be constituted by a relay in series with the supply for this electric motor, such that when the electric drive motor of the loom is supplied, this relay is energised (or de-energised), and vice versa when the motor is stopped.
A shaft or rotatable member of the loom is indicated 32 and is driven by the drive shaft 14 so that at each beat of the sley 11 this shaft or member effects at least one complete revolution. In what follows it will be supposed that the member 32 is effectively a shaft and that it effects exactly one revolution for each beat of the sley 11.
A vane or tab 33 is fixed to the shaft 32 and is associated with first and second passage sensors 34, 35 fixed to the loom. Each of these sensors comprises, for example, a photoemitter-photodetector pair located in a fork so that the radiation directed from the photoemitter to the photodetector is intercepted by the passage of the vane 33. The passage sensors 34 and 35 are located at two distinct angular positions which can be assumed by the vane 33.
The tachometric sensor 30, the electric motor 20, the loom operation sensor 31 and the passage sensors 34 and 35 described above are connected to a control and operating unit generally indicated 40 in Figure 1, housed in a container or housing 41 fixed to the loom. The circuit arrangement of one embodiment of the control and operating unit 40 will be described below with reference to the diagram of Figure 2. In this latter Figure devices already described above are again indicated by the same reference numerals.
The control and operating unit 40, as is apparent from Figure 2, includes a pulse shaping circuit 42 connected to the output of the tachometric sensor 30, a processing and memory circuit part generally indicated 43, and an execution and control circuit part generally indicated 44. The control and operating unit 40 also includes a circuit 45 for detecting the rotation of the shafts 32 and 14 in the opposite sense from normal, after the stoppage of the loom. This latter circuit is connected to the passage sensors 34 and 35 and the sensor 31 described above.
As will be apparent from the description below, the circuit part 43 is intended to effect its own processing principally during the normal operation of the loom while the circuit part 44 is called upon to operate mainly after a stoppage of the operation of the loom, in order to restore the desired predetermined working conditions.
The processing and memory circuit part 43 includes two counters 46, 47 of the type known in English terminology as "presettable up/down counters" having preset inputs 46a, 47a connected to a single presetting device 48. This latter may include switches of the "Contraves" type and a visual display device 48a for providing a visual indication of the numbers input manually by the switches, these numbers corresponding to the count module of the counters 46 and 47.
The counter 46 has its clock input 46b connected to the output of the pulse shaping circuit 42. The clock input 47b of the counter 47 is, however, connected to the passage sensors 34, 35 by an OR circuit 49.
A further counter indicated 50 has its count input 50a connected to the output of the counter 46 and its "reset" input 50b connected to the output of the counter 47 through a delay circuit 51.
The counter 50, which is of the binary type, has a plurality of parallel outputs 50c at which information bits are output in operation, which together indicate in binary code the instantaneous value reached by the counts effected by the counter. These outputs are connected in order to corresponding inputs of a memory device 52 having a corresponding plurality of outputs 52a and a loading control input 52b connected to the output of the counter 47.
The counters 46 and 47 may be constituted, for example, by integrated counters type 4516, the counter 50 may be formed by three integrated counters type 4520 and correspondingly the memory device 52 may comprise three type 40175 devices.
The circuit 45 for detecting rotation of the shafts 14 and 32 in the contrary sense includes a bistable circuit (flip-flop) of type D, indicated 60, having its data input connected to the output of one of the two passage sensors 34 or 35 and its clock input connected to the output of the other of these sensors. The output of the flip-flop 60 is connected to a first input of an AND gate 61, the second input of which is connected to the output of the sensor 31 for sensing interruption of the operation of the loom.
In operation, as long as the drive shaft 14 and the shaft 32 rotate in the normal sense, and thus the vane 33 continues to pass the passage sensor 35 and 34 in the same sequence, the flip-flop circuit 60 maintains the input of the AND gate 61 to which it is connected at the level "0".
When, for reasons which will be described below, after an interruption of operation the shaft 14 and the shaft 32 are made to rotate in the opposite sense from normal, the vane 33 passes the sensors 34 and 35 in the reverse of the normal order. The flip-flop circuit 60 correspondingly outputs a signal at the level "1" to the AND gate 61.
Consequently, the AND gate 61 may output an enabling signal at level "1" only when, in conditions in which the loom has stopped, the sensors 34 and 35 signal the rotation of the shafts 14 and 32 in the opposite sense from normal.
The execution and control circuit part 44 includes an AND gate 62 with a first input 62a connected to the tachometric sensor 30 through the pulse shaping circuit 42. A further input 62b of this gate is connected to the output of a circuit 63 for reversing the sense cf iotation of the motor 20, formed for example with relays, controlling the connection of the starting capacitor to the windings of the electric motor 20. The reversing circuit 63 has two inputs 63a and 63b for controlling the reversal.
The reversing circuit 63 is arranged to cause the reversal of the sense of rotation of the motor 20 when it receives a control signal at the input 63a and to restore the normal sense of rotation when it receives a command at the input 63b. Each time the reversing circuit switches the connection of the starting capacitor to predispose the motor 20 for the opposite sense of rotation from normal, when switching has occurred, it supplies an enabling signal at level "1" to the input 62b of the AND gate 62 and to an enabling input of a pilot circuit 64 for the motor 20, formed by SCR devices in known manner. The pilot circuit 64 is also connected to a speed regulating circuit 19. In normal operation of the loom, the input 62b of the AND gate 62 is maintained at level "0" whereby the output of the AND gate also remains at the level "0" preventing, as will be clarified below, the operation of all the devices of the execution and control circuit part 44 downstream of this gate.
The output of the AND gate 62 is connected to a first input 65a of an enabling logic circuit 65 having two outputs 65b, 65c connected respectively to the clock inputs 66a, 67a of two counters 66, 67 of the same type as the counters 46 and 47.
The logic circuit 65 is arranged so as normally to allow the passage of the signals from its input 65a to the input 66a of the counter 66. The signals supplied to its input 65a are instead directed to the input 67a of the counter 67 when a command signal is applied to a further input 65d of this logic circuit.
The counters 66 and 67 have respective manually operable devices 68 and 69 of the same type as the device 48 described above for the presetting of the counting module.
The "carry-out" output of the counter 66 is connected to the clock input of a counter 70 formed, for example, by three integrated circuits type 4516, with the preset inputs connected in order to the outputs 52a of the memory device 52. The output of the counter 70 is connected to a first input of an AND gate 71 having its output connected to the input 63b of the reversing circuit 63, to an enabling input of the pilot circuit 64 and to an actuator device 72 for controlling the brake (not illustrated) of the motor 20.
The counter 67 has its "carry-out" output connected to the clock input of a counter 73 of the same type as the counter 70 but having only a certain number of the preset inputs connected in order to corresponding outputs 52a of the memory device 52. In the embodiment illustrated, this memory device has twelve output terminals and the counter 73 has eight preset inputs connected to the eight outputs of the memory 52 corresponding to the less significant bits.
The counters 70 and 73 may each comprise three type 4516 integrated circuits connected together in cascade.
The counter 73 has its output connected to a second input of the AND gate 71.
The execution and control circuit part 44 also includes "sample and hold" circuit 90 having its sampling input connected to the voltage divider including the photoresistor 18, a memory device 91 connected to this sample and hold circuit through an analogue/digital converter 92. The memory 91 is connected to a digital/analogue converter 93, the output of which is connected to a first input of a switching device 94. This latter has another input connected to the divider including the-photoresistor 18 and its output connected to the input for the reference voltage of the speed regulator 19.
The sample and hold circuit has its clock input connected to a timing device 95 arranged to output a pulse at each beat of the sley 11. This device may be formed for example in the following manner. A vane 95a (Figure 1) is fixed to the main shaft 14 of the loom; this vane has an associated passage sensor 95b, for example of the same type as the passage sensors 34, 35 described above. In an extreme case, the timing device 95 could be constituted by the vane 33 and by one of the passage sensors 34, 35.
In normal operation of the loom, at each beat, the value (sampled by the sample and hold circuit 90 and converted into digital form by the converter 92) of the reference voltage supplied to the speed regulator 19 when the vane 95a passes the sensor 95b is stored in the memory 91. This stored value is indicative of the speed of rotation imposed on the motor 20 during the beating-up.
In weaving with a very irregular weave, the tension of the warp threads may vary considerably and in a pulsed manner during each individual beat, for example following the movement of the healds. Consequently the value of the reference voltage may vary considerably (about its average value) during each individual beat. In this case, by suitable choice of the angular dimension of the vane 95a and with suitable positioning of the vane 95a on the shaft 14 or of the sensor 95b, it is possible to make the sampling of the reference voltage occur in one portion of the beat cycle in which the reference voltage is substantially free from sharp variations.
A timer 96 has an input connected to the sensor 31 for sensing the operation of the loom, and an output connected to the control input of the switching device 94. This latter normally connects the speed regulator 19 to the divider including the photoresistor 18. The sensor 31 is also connected to the block input of the memory 91.
The device according to the invention described above operates as follows.
It will be supposed that the loom to which it is applied operates regularly.
Under these conditions, the diameter of the warp wound on the beam diminishes progressively and its speed of rotation increases correspondingly. The tachometric sensor 30 thus outputs pulses at a high frequency, this frequency increasing with time as the diameter of the beam diminishes.
At the same time, the passage sensors 34, 35 supply the counter 47 with a pulse at each beat, and thus each time a weft thread is inserted.
The counters 46 and 47 output a pulse for each N pulses received, N being the number input by means of the presetting device 48.
The counter 50 thus counts at a frequency N times less than the frequency of the pulses supplied to the input of the counter 46 and presents the indication of the count value reached at the output 50c in the form of a combination of twelve bits in parallel.
For each N wefts inserted, the counter 47 outputs a command to the memory device 52 which thus "reads" and stores the outputs of the counter 50; the counter 47 then sets the counter 50 to zero and the cycle starts again.
In essence, after each insertion of N successive wefts, the memory device 52 stores the average number of pulses emitted by the tachometric sensor for the insertion of a weft. This average value is clearly indicative of the average angular movement of the beam 2 effected for each beat, this average being effected on the last N wefts inserted. In other words, after the insertion of N wefts the memory 52 will have stored data indicative of the average length of warp unwound at each beat.
The presetting device 48 allows a variation of the number N between a minimum N = 1 and a predetermined maximum and hence allows a variation in the dimension of the sample from which the average is derived.
In normal operation of the loom, as stated above, the AND gate 62 is "blocked" and hence the counters 66, 67, 70, 73 are inactive. The output of the AND gate 71 is at level "0" and the reversing circuit 63 enables the rotation of the electric motor 20 in the normal sense, that is, in the sense in which it allows the unwinding of the chain from the beam.
The shaft 32, under normal operating conditions of the loom, continues to rotate in the same sense, and hence the sequence with which the vane 33 passes the sensors 34 and 35 is always the same. Consequently the output of the AND gate 61 is kept at the level "0".
In normal operation, at each beat the memory 91 stores data indicative of the speed of rotation of the motor 20.
Supposing now that the weft breaks or is exhausted. Weft-feeler sensor devices (not illustrated) of known type cause the stoppage of the loom. After one or more empty beats of the sley 11, the drive shaft 14 finally stops. As a result of the empty beats, the boundary line between shed and the woven textile is moved further towards the piece beam.
Immediately the operation of the loom is interrupted, the sensor 31 causes the "freezing" in the memory 91 of the data indicative of the (average) speed of the motor 20 immediately before the interruption.
In order to allow the removal of the broken weft, the shed is returned to the open configuration, in the condition in which the last weft (that broken) was inserted. This may be achieved manually, for example by rotating the drive shaft 14 in the opposite sense from the normal sense of rotation. This operation is, however, achieved automatically in some more recent looms.
Upon the said rotation of the shaft 14 the sensors 34, 35 cause the output of the AND gate 61 to change to the level "1" and consequently the reversing circuit 63 is disposed to rotate the motor 20 in the opposite sense. With reversal accomplished, the reversing circuit brings the input 62b of the AND gate 62 to level "1".
The latter is thus "open" to allow the pulses from the tachometric sensor 30 to pass to the logic circuit 65. The pilot circuit 64 is actuated and the motor 20 rotates in the opposite sense to the sense in which it rotates in normal operation of the loom. This motor thus starts to rotate, rotating the beam 2 in the opposite sense from normal, causing the rewinding of the chain 3. The tachometric sensor 30 outputs a pulsed signal at a frequency indicative of the speed of rotation of the motor 20 to the logic circuit 65 through the AND gate 62. This logic circuit passes these pulses to the counter 66. The latter outputs a pulse to the counter 70 for each M pulses received, M being the number set-in by the presetting device 69. The number M represents the ratio between the desired drawing back of the textile warp and the average length of warp unwound at each beat in the last group of N wefts inserted just before the stoppage of the loom. This number M may be set-in manually and established previously in dependence on the characteristics of the loom (in particular the number of empty beats which the sley of the loom typically carries out after breakage of the weft, before the effective stoppage of the loom), the characteristics of the thread used and the characteristics of the weave being carried out.
The counter 70 in turn divides the frequency of pulses received by the number stored in the memory device 52 at the moment of stoppage of the loom. If this number is indicated L, then after the counter 70 has received L pulses, it outputs a "1" to the AND circuit 71 and to the input 65d of the logic circuit 65. This latter circuit then uncouples the counter 66 from the tachometric sensor 30 and the counter 67 is coupled to this sensor.
Up to this moment, starting from its activation in the reverse sense, the motor 20 has caused rewinding of the warp beam by an amount equivalent to M times the average length of warp unwound on average for each weft for the last group of N wefts before the stoppage of the loom.
As will become apparent below, the counter 67, now coupled to the tachometric sensor 30, and the counter 73 at this point enable a possible further rewinding of the warp beam to an extent equal to a predetermined fraction of the said average value of the warp length unwound at each beat before the stoppage of the loom. This occurs as follows.
The counter 67 outputs a pulse for each m pulses received, m being the number set-in by means of the presetting device 69.
In the embodiment shown in Figure 2, the preset inputs of the counter 73 are connected to all the outputs of the memory device 52a, except for the four outputs relating to the most significant bits. Accordingly in this embodiment, the counter 73 counts up to the number L/8. Consequently, after the counter 67 has received mL/8 pulses, the counter 73 also outputs a "1" to the AND gate 71, the output of which thus changes to the level "1", causing the activation of the brake of the motor 20 through the actuator device 72, and the reswitching of the reversing circuit 63, disposing the motor 20 for subsequent rotation in the sense corresponding to the normal operation of the loom.
In the embodiment illustrated, the counters 67 and 73 thus allow a supplementary rewinding of M eighths of the average value of the length of warp unwound for each weft in the last group of N wefts inserted before the stoppage.
The possibility of achieving rewinding of the warp to an extent corresponding to a whole multiple plus a predetermined fraction of the said average value is very important in that it allows extremely accurate positioning in the boundary line between the warp and the woven textile on resumption of operation of the loom, and in particular allows compensation for any micro-displacements due to the resilient yielding of the threads and also compensation for any foreseeable weakness in the first beat effected by the sley upon resumption of operation.
For weaving with a warp constituted by threads which are prone to extensive inelastic yielding it may be useful to connect the counter 67 or the counter 66 (or both) to a timer device (not illustrated) arranged to increase (or decrease) the count by one or more units after a predetermined time from the start of the interruption. By virtue of such a counter (which may be activated for example by the sensor 31 when a stoppage of the loom is detected) it is possible to recover any elongation undergone by the warp.
At the end of the operations described above and removal of the broken weft, normal operation of the loom may be started and the formation of any barre in the textile is avoided.
Upon restarting the loom, the sensor 31, through the timer 96, causes the switching device 94 to change (for a predetermined period) to the condition in which it causes the application (through the converter 93) of the reference voltage stored in the memory 91 to the speed regulator 19. Thus on restarting, it is ensured that the speed of the motor 20 is substantially equal to the speed which it would have had if the interruption had not occurred.
Naturally, the principle of the invention remaining the same, embodiments and details of construction may be varied widely with respect to those described and illustrated purely by way of non-limiting example, without thereby departing from the scope of the present invention.
Thus, among possible variants, between the converter 92 and the memory 91 there may be provided a processing and averaging circuit arranged to average, over a predetermined number of beats, the sampled values of the reference voltage supplied to the speed regulator.
Furthermore, the direct connection between the divider, including the photoresistor 18 and the regulator 19 may be eliminated: in this case this regulator would be piloted constantly with a reference voltage derived by means of sampling during the preceding beat or during a predetermined number of preceding beats.
Finally, between the timing device 95 and the sample and hold circuit 90 there may be interposed a counter (indicated 150 in Figure 2) of the same type as the counters 46 and 47, provided with a presetting device (indicated 151) such as the device 48. This device would allow sampling of every Kth beat, K being the number input by the presetting device 152.
3. Device according to Claim 2, characterised in that the control and operating circuit means (40) are arranged to cause rewinding of the warp to an extent corresponding to a whole multiple of the average value.
1. Device according to Claim 2, characterised in that the control and operating circuit means (40) are arranged to cause rewinding of the warp (3) to an extent corresponding to a whole multiple plus a predetermined fraction of the average value.
5. Device according to Claim 3 or 4, characterised in that the control and operating circuit means (40) include first manually operated input means (68, 69) for enabling the input of the quantitative value of the drawing back of the warp (3).
6. Device according to any one of Claims 2 to 5, characterised in that the processing circuit means (46 to 48) include second manually operable presetting means (48) arranged to enable the input of the number of consecutive beatings up over which the said average value is calculated.
7. Device according to any one of the preceding claims, characterised in that it further includes sensor means (31) for sensing the condition of interruption of operation of the loom, connected to the control and operating circuit means (40), and in that these circuit means (40) are arranged to cause the rewinding of the warp (3) on the beam (2) only after the sensor means (31) have indicated an interruption in the working of the loom.

Claims

1. Device for restoring a loom to predetermined operative conditions to renew working after an interruption, particularly after breakage of the weft, characterised in that it includes:.

- detector means (30; 34, 35; 50) for providing electrical signals indicative of the length of warp unwound at each beating-up in normal operation of the loom,

- memory means (52) connected to the detector means for storing signals indicative of the warp length unwound at each beating-up,

- drive means (20, 21) for causing rewinding of the warp (3) on the warp beam (2), and

- control and operating circuit means (40) connected to the detector means (30; 34, 35; 50), to the memory means (52) and to the drive means (20) and arranged after an interruption in the working of the loom to actuate the drive means (20) to cause rewinding of the warp (3),and corresponding drawing back of the woven textile(T)to an extent which is in a predetermined ratio to the last value of warp length stored in the memory means (52) before the interruption.

2. Device according to Claim 1, characterised in that it further includes processing circuit means (46 to 48) connected between the detector means (30; 34, 35) and the memory means (52) for determining cyclically the average value of the warp length unwound at each beating-up for a predetermined number (N) of consecutive beatings up, and to provide electrical signals indicative of this average value to the memory means (52).

8. Device according to any one of the preceding claims, particularly for a loom having a warp-tension adjusting device including an electric motor for moving the beam (2) for the warp (3), characterised in that the said drive means are constituted by the electric motor (20) of the warp-tension adjusting device (3).

9. Device according to any one of Claims 1 to 7 and Claim 8, particularly for a loom (1) having a warp-tension adjusting device (3) including

- an electric motor (20) for controlling the warp beam (2),

- a regulating circuit (19) for modifying the rate of rotation of the motor (20) in dependence on a reference voltage value, and

- a sensor device (15 - 18; 5 - 8)for sensing the tension of the warp (3) and for providing the regulating circuit (19) with a reference voltage which is variable in dependence on the tension of the warp (3),

characterised in that it further includes

- second detector means (95; 90, 92) for providing electrical signals indicative of a value assumed by the reference voltage at each beating-up in normal operation of the loom (1); and

- second memory means (91) connected to the detector means (95; 90, 92); and in that the control and operating circuit means (44) are arranged, on resumption of normal operation of the loom after an interruption, to cause the restarting of the electric motor (20) at a speed which is in a predetermined relationship with the last value of the reference voltage stored in the second memory means (91) before the interruption.

10. Device according to Claim 8 or 9, characterised in that the detector means include:

- speed sensor means (30) coupled to the electric motor (20) for providing in operation a pulsed signal of a frequency indicative of the rate of rotation of the motor (20) and hence of the rate of unwinding of the warp (3) from the beam (2),

- sensor means !34, 35) for sensing the frequency of beating-up, associated with the sley (11) of the loom, arranged to provide an electrical pulsed signal of a frequency indicative of the frequency with which the sley (11) of the loom effects beating-up of the weft in operation, and

- counting means (50) connected to the speed sensor means (30) and the sensor means (34, 35) for the frequency of beating-up, arranged to count cyclically the pulses provided by the speed sensor means (30) during normal operation of the loom between predetermined pairs of pulses output by the sensor means (34, 35) for the beating-up frequency and for supplying corresponding signals to the memory means (52) at the end of each count.

11. Device according to Claims 7 and 10, characterised in that the memory means (52) are connected to the sensor means (31) for sensing the interruption of operation of the loom and are arranged to store data supplied thereto by the counting means (50) until the sensor means (31) indicate an interruption in the operation of the loom.

12. Device according to Claims 2 and 10, characterised in that the processing circuit means include first and second digital counters (46, 47) of the presettable modular type, having respective count inputs connected to the speed sensor means (30) and to the sensor means (34, 35) for sensing the frequency of beating-up respectively; the first and second counters (46, 47) being arranged to count up or to count down the same predetermined modulus.

13. Device according to Claims 10 and 12, characterised in that the counter means include a counter (50) with an input clock (50a) connected to the output of the first presettable modular digital counter (46), and the reset input (50b) connected to the output of the said second presettable modular digital counter (47) through a delay device (51); the counter device (50) having a plurality of parallel type outputs (50c) in correspondence with which, in operation, information bits are output which together indicate the instantaneous value of the contents of the counter device (50) in a predetermined code.

14. Device according to Claims 10 to 13, characterised in that the sensor means for sensing the frequency of beating-up include a first photo-emitter and a first photo-sensor (34) facing each other, mounted in respective fixed positions on the loom, and a rotatable interceptor member (33) coupled to the drive shaft (14) of the loom directly or indirectly so that the interceptor member (33) effects at least one revolution for every beat of the sley (11) and correspondingly, at each revolution, passes through the region between the photoemitter and the photodetector.

15. Device according to any one of Claims 8 to 14, particularly for a loom in which the beam (2) is driven by a single-phase induction motor(20) with a starting capacitor and in which, after breakage or exhaustion of the weft, the shed (10) is returned manually or automatically to the condition in which the insertion of the broken or incomplete weft occurred by rotation of the drive shaft (14) of the loom in the opposite sense to normal, characterised in that it further includes.

- detector means (34, 35; 60) for detecting the rotation of the main drive shaft (14) of the loom in the opposite sense, and

- the control and operating circuit means (40) include a circuit (63) for switching the connection of the starting capacitor of the electric motor (20) connected to the detector means (34, 35; 60) and arranged to pre-dispose the motor (20) for rotation in the opposite sense only after the detector means (34, 35; 60) indicate the rotation of the drive shaft (14) in the opposite sense from normal.

16. Device according to Claim 15, characterised in that the reversing.circuit(63) is enabled to pre-arrange reversal of the sense of rotation of the said motor (20) only after the sensor means (31) have indicated a condition of interruption of the operation of the loom.

17. Device according to Claims 14 and 15, characterised in that the interceptor member (33) is also associated with a second photoemitter and a second photodetector (35), mounted in facing relationship in respective fixed positions on the loom, and in that the means (34, 35; 60) for detecting the reverse rotation of the drive shaft (14) of the loom include means (60) for discriminating between the order in which the interceptor member (33) passes between the first photoemitter and the first photosensor (34) and between the second photoemitter loom, to connect the memory device (91) to the speed regulator (19) for a predetermined period of time upon restarting of the loom after an interruption and to reconnect the sensor device (5-8; 15-18) to the speed regulator (19) at the end of the said predetermined period.

22. Device according to any one of Claims 19 to 21, characterised in that a presettable modular counter device (151) is connected between the timing device (95) and the sample and hold circuit (90).
and the second photosensor (35).

18. Device according to Claim 17, characterised in that the means (34, 35; 60) for detecting the reverse rotation of the drive shaft (14) of the loom include a D-type flip-flop (60) having a data input connected to one of the photosensors and a clock input connected to the cther photosensor.

19. Device according to Claim 9, characterised in that the second detector means include:

- a timing device (95) for outputting a command signal at each beat of the sley (11) during normal operation of the loom,

- a sample and hold circuit (90) connected to the device for sensing the warp tension (5-8; 15-18) and to the timing device (95) for sampling a value of the reference voltage at each beat, and a memory device (91) for storing data indicative of the values sampled by the sample and hold circuit.

20. Device according to Claim 19, characterised in that an analog/digital converger (92) is interposed between the sample and hold circuit (90) and the memory device (91) and a digital/analog converter (93) is interposed between the memory device (91) and the speed regulator (19).

21. Device according to Claim 19 or 20, characterised in that it includes a switching device (94) connected between the device (5-8; 15-18) for sensing the warp tension, the memory device (91) and the input of the speed regulator (19); the switching device (94) being arranged to connect the sensor device (5-8); 15-18) to the speed regulator (19) during normal operation of the