BE1018921A5 - APPARATUS FOR ADJUSTING THE INSERTION OF THE FRAME WIRE FOR A JET WEAVING. - Google Patents

Abstract

A weft yarn insertion adjustment apparatus in a jet loom includes a weft yarn path modification device (21A, 21B) and a control computer (C). The protection setting is implemented when the normal setting is inactive. This configuration makes it possible to extend the life of at least one bearing (29) in the stepping motor (Ma, Mb).

Description

Apparatus for adjusting the insertion of the weft thread for a jet loom.

The present invention relates to a weft yarn insertion control apparatus for a jet type loom.

BASIS OF THE INVENTION

The theft of a weft yarn in a jet loom ends when the weft yarn is removed from a weft length measuring storage device. Stopping the withdrawal of the weft yarn quickly stops the flight of the weft yarn which is flying at a high speed, which increases the tension of the weft yarn. The rapid increase in tension can lead to a break in the weft thread. To prevent the latter, a weft yarn braking device is used which changes the weft thread path immediately before completion of weft thread insertion in order to suppress the rapid increase in tension.

A device of this type for the braking of the weft thread is disclosed for example in the Japanese publication subject to the public inspection number 2005-42254 and in EP 1 258 550. The device disclosed in this patent application uses a motor not to not for driving a moving body for moving a weft thread. Braking is applied to the weft yarn directly prior to the completion of weft insertion by exerting a deflection resistance of the weft yarn flexed by the moving body contacted with the weft yarn.

A rotor shaft of a stepper motor or impulse motor is supported by a bearing lubricated with grease.

The span or magnitude of rotation of the stepper motor rotor shaft is set to be smaller than the angle at which the bearing elements (balls or rollers) in the bearing rotate, taking into account an appropriate braking value. However, when the rolling elements rotate within a span of less than one revolution, the grease may not spread over the entire surface of the rolling elements. As a result, the motor bearing may be damaged by the vibrations of the loom during weaving. These degradations shorten the life of the bearing.

SUMMARY OF THE INVENTION

An object of the present invention is to extend the life of a bearing in an actuator used for a weft path change device.

In one aspect of the invention, there is provided a weft insertion control apparatus in a jet loom, comprising a weft path change device and a controller. The weft path change device includes a path modifier for changing the path of a weft yarn and an actuator for driving the path modifier, wherein the controller adjusts the operational position of the actuator. The controller has the function, in the case of a normal adjustment, to adjust the operational position of the actuator so that the position of the path modifier changes to change the path of the weft thread, and function, in the protective setting frame, for subjecting the trajectory modifier to reciprocating movement such that the span (Θ) of the position change of the trajectory modifier (20) becomes greater than the span of the position change of the path modifier 20 during normal setting The protection setting is implemented when the normal setting is inactive.

In accordance with this configuration, the protection setting, in which the trajectory modifier moves back and forth the span of the trajectory modifier position change to make it larger than the span of the change. the position of the path modifier during normal adjustment, is implemented when the normal setting is inactive. As a result, grease is spread over the entire surface of the rolling elements in a bearing of the actuator.

In a preferred embodiment, the controller implements the protection setting during a period during which weaving is stopped.

According to this configuration, the protection setting is implemented when the weaving is stopped, the latter being accompanied by phenomena of malfunction of insertion of the weft thread or breakage of the warp thread. This means that the protection setting has a sufficient period of time, so that a spread of the grease is ensured over the entire surface of the rolling elements of a bearing of the actuator.

In a preferred embodiment, the controller implements the protection setting when stopping the weaving takes place after a predetermined reference period of time has elapsed when the controller supply is open or from the moment corresponding to the end of the previous protection setting.

The reference period of time is, for example, approximately 10 hours. It is necessary that the grease spread over the entire surface of the rolling elements, a lubrication of the rolling elements is maintained in good condition for a long time.

In a preferred embodiment, the actuator is a rotary actuator including an encoder, wherein the position of the rotary actuator is adjustable. The path modifier is attached to an output shaft of the rotary actuator. The controller implements the protection setting after placing the trajectory modifier in its initial position in which the operational position of the rotary actuator can be identified.

According to this configuration, a protection setting is implemented after identifying the initial position. Therefore, the placement of the trajectory modifier in an undesirable position can be prevented.

In a preferred embodiment, the controller places the path modifier in a standby position when the normal setting is inactive and returns the path modifier to its standby position after the setting of the protection setting.

According to this configuration, the trajectory modifier moves in a predetermined manner. As a result, a breakage of the weft thread during weaving restart can occur more quickly.

In a preferred embodiment, the span of the angle of rotation of the path modifier in the protection setting represents the span in which a rolling element performs one or more rotations.

Other aspects and advantages of the invention will become apparent from the following description when taken in conjunction with the accompanying drawings which illustrate by way of example the principles of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention, together with its objects and advantages, will be better understood by reference to the following description of the presently preferred embodiments in conjunction with the accompanying drawings in which: Figure 1 (a) is a partially cutaway plan view of a jet loom according to one embodiment of the invention; Fig. 1 (b) is a block diagram of the control of the loom of Fig. 1 (a); Figure 2 is a partially cut away rear view of the jet loom of Figure 1 (a); Figure 3 (a) is a partially cut away side view of the jet loom of Figure 1 (a); Fig. 3 (b) is a partially enlarged side view of the weft braking device; Figure 4 is a partially cut away rear view of the jet loom of Figure 1 (a); Figure 5 is a partially cutaway rear view of the jet loom of Figure 1 (a); Figure 6 is a diagram illustrating a program for the protection setting implemented by a control computer.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

A jet loom capable of weaving using two types of weft yarn according to preferred embodiments of the invention will be described with reference to Figures 1 to 6.

As illustrated in FIG. 1 (a), a weft yarn Ya is wound and stored over a weft winding face 112 by the rotation of a weft yarn winding tube 111. of a storage device for measuring the length of the weft thread 11, of the winding type. The weft yarn Ya which is wound over the winding face of the weft yarn 112 is removed from the winding face of the weft yarn 112 by the action of projecting pressurized air supplied by a tandem nozzle 13A and by the action of projecting the pressurized air from a main nozzle 14A for the insertion of the weft yarn in a state in which the weft yarn Ya is removed from its contact with a contact pin 121 driven by an electromagnetic solenoid 12. The main nozzle 14A oscillates in concert with a non-illustrated comb which is beaten because the comb is not beaten. The tandem nozzle 13A represents a type of nozzle for insertion of the weft yarn, which presses the weft yarn towards the main nozzle 14A. the contact pin 121 deviates from the winding face of the weft wire 116 on the basis of a magnetic command sent by a control computer C to the electromagnetic solenoid 12.

A detached weft detector 10, which represents a reflection-type photoelectronic detector, is provided near the weft winding face 112. The detector 10 detects the weft yarn Ya when the latter is removed and spaced from the weft winding face 112 and this detection signal is sent to the control computer C. When the number of times corresponding to the detachment of the weft yarn Ya reaches a predetermined number, the computer command C orders the demagnetization of the electromagnetic solenoid 12 so as to contact the contact pin 21 with the weft winding face 112. When the contact pin 21 is brought into contact with the weft yarn winding face 112, subsequent removal of weft yarn Ya is prevented. The portion of the weft yarn Ya already removed from the weft winding face 112 is inserted into an opening formed between the warp yarns not illustrated by the action of the jet of air emanating from the main nozzle 14A.

As illustrated in FIG. 3 (a), the tandem nozzle 13A is inserted into a nozzle body in the form of a square tube. The tandem nozzle 13A includes a wire guide 16 threaded into the tube of the nozzle body 15. An air supply pipe 17 is connected to the lateral side of the nozzle body 15. Pressurized air feeds the tandem nozzle 13A via the air supply pipe 17 from a pressurized air supply source not shown.

As illustrated in FIG. 1 (A), an angular connecting plate 18 is attached to the rear of the nozzle body 15. The connecting plate 18 includes a flat base portion 181 connected to the rear of the nozzle body 5 and a plane auxiliary portion 182 connected to the base portion 181 at an angle to the base portion 181. A stepper motor Ma is attached to the base portion 181 and includes a rotary encoder 19. An engine shaft 28 of the stepping motor Ma protrudes through the base portion 181 and a bar-shaped path modifier 20 is attached to the protruding portion of the motor shaft 28 protruding from the portion The stepper motor Ma is an actuator for driving the trajectory modifier 20 including an encoder. The position of the actuator is adjustable. The stepper motor Ma and the trajectory modifier 20 constitute a braking device of the weft yarn 21A acting as a device for modifying the trajectory of the weft yarn.

As illustrated in FIG. 3 (b), the motor shaft 28, in the form of an output shaft, is rotatably supported in a motor housing 30 via a pair of radial bearings 29. Grease is placed between the outer ring 291 and the inner ring 292, the two rings constituting a respective radial bearing 29.

As illustrated in FIG. 1 (a), a block 22 is fixed to the auxiliary portion 182 of the connecting plate 18 and a circular plate 23 represents a disk 23 fixed to the block 22. A guide ring 24 is fixed to the block 22 to penetrate through the block 22 and through the disc 23. We pass the weft yarn Ya through the guide ring 24 to the tandem nozzle 13A.

A support shaft 25 is attached to the lateral side of the nozzle body 15. A column 27 supports the support shaft 25 via a connecting member 26. The column 27 is supported by a side frame of a loom via a support not shown.

The weft yarn Yb illustrated in FIG. 1 (a) is inserted into the opening formed between the warp threads by the action of an air jet of the tandem nozzle 13B and the main nozzle 14B. A weft braking device 21B, which acts as a weft path change device, is attached to the tandem nozzle 13B. The weft braking device 21B has the same configuration as that of the weft braking device 21A and a stepping motor of the weft braking device 21B is designated by the stepper motor Mb. Identical elements are designated by identical reference numerals and their detailed description is omitted.

As illustrated in FIG. 1 (b), the stepper motors Ma and Mb are controlled by the control computer C. The control computer C controls the operations of the stepper motors Ma and Mb based on the information This is achieved by detecting the rotation angle of the loom via a rotary encoder 34 which detects the rotation angle of the loom. Immediately before starting the insertion of the weft yarns Ya and Yb, each path modifier 20 is in a standby position St indicated by the solid line, so that each weft yarn Ya, Yb does not enter. in contact with the corresponding trajectory modifier 20, as illustrated in FIG. 2.

In the case in which the weft yarn Ya has been inserted, when a loom forming a predetermined angle of rotation, the control computer C orders the magnetization of the solenoid electromagnetic 12 in the storage device of the measurement of the length of the weft yarn 11 to move the contact pin 121 away from the weft winding face 112. The weft yarn Ya, which is no longer in contact with the contact pin 121 under the action of a fluid or an air jet coming from the tandem nozzle 13A and the main nozzle 14A is ejected from the main nozzle 14A. During the insertion period of the weft yarn Ya, we may be confronted with a ballooning of the weft yarn Ya between the storage device for measuring the length of the weft thread 11 and the guide ring 24. However, the disk 23 prevents this bloat from interfering with the stepper motor Ma.

When approaching the completion of the insertion of the weft yarn Ya, the control computer C sets the operating position of the stepper motor Ma so that the modifier of the path 20 of the motor step Ma is rotated from the waiting position St indicated by the solid line to the braking position of the weft thread Br indicated by the dashed line in FIG. 2. The span of the angle of rotation in FIG. changing from standby position St to the braking position of the weft thread Br is indicated by Θ1. When the stepper motor path modifier 20 Ma is in the braking position of the weft wire Br, the weft yarn Ya takes a second path of the yarn along which the weft yarn Ya comes into contact with. the path modifier 20 and is flexed between the guide ring 24 and the wire guide 16, as illustrated by the dotted line in Figs. 3 (a) and (b).

When the electromagnetic solenoid 12 is demagnetized to allow the contact pin 121 to contact the wire winding face 112 of the storage device for measuring the length of the weft yarn 11, it is prevented. removing and detaching the weft yarn Ya, thereby bringing the insertion of the weft yarn to completion.

When the weft yarn Ya is inserted along the first voice of the weft yarn as indicated by the solid lines in FIGS. 3 (a) and (b), the trajectory of the weft yarn Ya between the guide ring 24 and the wire guide 16 is linear in the absence of contact with the path modifier 20. As a result, the resistance experienced by the weft yarn Ya during insertion of the weft yarn along the first path of the thread is minimal. When the weft yarn Ya is shifted to follow the second path of the yarn near the completion of the insertion of the weft yarn, the weft yarn Ya flexes, so that a flexural strength is exerted on the Ya weft thread. The bending resistance caused by the deflection in the second path of the wire exerts on the weft yarn Ya a braking action during its insertion. This braking action, provided by the path offset of the weft yarn Ya that passes from the first yarn path to the second path near the completion of the weft insertion, reduces the insertion speed of the yarn. weft yarn Ya so as to prevent a rapid increase in the tension exerted on the weft yarn Ya at the time of the completion of the insertion of the weft yarn. As a result, we can avoid a breakage of the weft yarn Ya, due to a rapid increase in tension.

A similar braking action is exerted on the weft yarn Yb during insertion of the weft yarn Yb.

As illustrated in FIGS. 1 (b), 2, 3 (a) and 5, an input device 31 and a display device 32 are signal-connected to the control computer C. The rotary encoders 19 of the motors Step by step Ma and Mb are also signaled to the control computer C. The control computer C receives positional information from the rotary encoders 19 in the stepper motors Ma and Mb.

As illustrated in FIG. 2, a protrusion 37 defining the initial position of each trajectory modifier 20 is fixed to the base portion 181 of the corresponding connecting plate 18. Each trajectory modifier 20 of the stepper motors Ma and Mb can enter in contact with the corresponding protrusion 37. When the trajectory modifier 20 is in its initial position Ge (as shown in FIG. 4), in which the trajectory modifier 20 comes into contact with the protrusion 37, the control computer C determines that the rotational position of the corresponding stepper motor Ma or Mb is in its initial position.

A display of the display device 32 shown in Figs. 1 (b), 2, 3 (a) and 5 displays the information entered in the control computer C after the handling of the input device 31. The letters "Ma And "Mb" indicated on the screen of the display device 32 refer to the stepper motors Ma and Mb, respectively. The word "ON" indicated below the letters "Ma" and "Mb" on the screen of the display device 32 illustrated in Figures 1 (b) and 2 indicates that the control computer C is set in the normal setting in which the control computer C receives the positional information from the rotary encoders 19 of the stepper motors Ma and Mb to adjust the operational position or rotation of the stepper motors Ma and Mb.

In the normal adjustment mode, as illustrated in FIGS. 1 (b) and 2, the two weft yarns Ya and Yb are used for weaving. However, when the weft yarn Ya is involved in a weft insertion cycle, the stepper motor path modifier Mb is in the pull back position of the weft yarn Pu as indicated by the dotted in FIG. 2. In the pull back position of the weft yarn Pu of the stepper motor path modifier Mb Mb, the distal end of the weft yarn Yb is drawn back into the nozzle from the end of the tube of the main nozzle 14B. Meanwhile, in the insertion cycle of the weft yarn Yb, the stepper motor path modifier 20 Ma is located in the pull back position of the weft yarn Pu as indicated by the dashed lines in FIG. In the pull back position of the weft yarn Pu of the stepper motor path modifier 20 Ma, the distal end of the weft yarn Ya is pulled back into the nozzle from the end of the tube of the main nozzle 14A.

The trajectory modifier 20 is located in the pull back position of the weft yarn Pu once the trajectory modifier 20 is in the braking position of the weft yarn Br. The span of the angle of rotation Θ2 the trajectory modifier 20, which extends in the range from the standby position St to the pull back position of the weft thread Pu, is greater than the span of the rotation angle φ1 of the trajectory 20, which extends in the range from the standby position St to the braking position Br. The reason why the distal end of the uninserted weft yarn is drawn back into the main nozzle 14A or 14B is to prevent the distal end of the uninserted weft yarn from interfering or becoming entangled with the weft yarn being inserted.

The word "OFF" indicated below the letters "Mb" on the screen of the display device 32 illustrated in FIG. 3 (a) and in FIG. 5 denotes the information entered into the control computer C after the manipulation of the device. The word "OFF" indicates that the control computer C is put in the standby mode, in which the control computer C receives the positional information from the rotary encoders 19 of the motor. not Mb to set the operating position of the stepper motor Mb, so that the stepper motor Mb maintains the path modifier 20 in the standby position St whenever the loom is working.

As illustrated in FIG. 5, in the state in which the word "OFF" appears below the characters "Mb" on the screen, the trajectory modifier 20 of the stepper motor Mb is maintained in the standby position St and the Yb frame can not be used. The path modifier 20 of the stepper motor Mb can be switched from the waiting position St to the braking position of the weft wire Br, and vice versa, and it can never be placed in the retracted position. by pulling the weft thread Pu (as can be seen in FIG. 4).

A weaving start switch 35 and a weaving dysfunction detector 36 are signaled to the control computer C. When the weaving start switch 35 is turned "ON", a weaving start signal is inputted. in the control computer C. The weaving dysfunction detector 36 may include a detector for detecting malfunctions of insertion of the weft thread or a detector for detecting breaks in the warp thread, and it sends a signal of stopping weaving at the control computer C when the weaving malfunction appears.

Fig. 6 is a flowchart in which a program for the protection setting implemented by the control computer C is illustrated. The protection setting will be described with reference to this flowchart. When it is activated, the control computer C places the trajectory modifiers 20 of the stepper motors Ma and Mb in their initial positions Ge in order to identify the positions in rotation of the stepper motors Ma and Mb and sets implement the setting to advance the trajectory modifiers 20 in the standby position St. Control computer C also measures the elapsed time from the opening ("ON" position) or from the completion of the previous protection setting.

The control computer C waits for the input of the weaving start signal (step S1). When the weaving start signal is inputted (YES at step S1), the control computer C starts its adjustment for weaving, including the demagnetization control of the electromagnetic solenoid 12 and the adjustment of the operating positions of the motors step by step Ma and Mb (step S2).

After starting weaving, the control computer C waits for the input of the weaving stop signal (step S3). When the weaving stop signal is inputted (YES in step S3), the control computer C stops weaving control, including the electromagnetic solenoid 12 demagnetizing control and the motor operating position adjustments step step by step Ma and Mb (step S4). At this time, the trajectory modifiers 20 are placed in the waiting positions St.

After stopping the weaving, the control computer C determines whether a reference period H has taken place from the ON opening or from the completion of the previous protection setting (step S5). . The course of the reference period H relates to the course of the period from the completion of the previous protection setting when the current protection setting is not the first. When the current protection setting is the first, the course of the reference period H relates to the course of the period extending from the switching on of the control computer C. When the reference period H is elapsed (YES in step S5), the control computer C intervenes to set the initial position (step S6). The command for the placement of the initial position takes place to place each trajectory modifier 20 in its initial position Ge, as illustrated in FIG. 4.

After the course of step S6, the control computer C rotates each trajectory modifier 20 placed in its initial position Ge to the extent of the angle of rotation Θ (see Figure 4) and returns it. at its initial position Ge (step S7). The span of the rotation angle Θ is greater than the span of the rotation angle Θ2 extending in the range from the standby position St and the pull back position of the weft yarn Pu.

In the lubrication position Ju (see FIG. 4), in which the trajectory modifier 20 rotates from its initial position Ge to the span of the rotation angle Θ, the weft yarn is drawn in return beyond the pulling position in return of the weft thread Pu of the trajectory modifier 20. However, the span of the rotation angle Θ is set relative to a span in which the weft yarns Ya and Yb remain in the main nozzles 14A and 14B, and with respect to the span in which the balls 293 of the radial bearing 29 perform one or more revolutions.

After step S7, the control computer C intervenes to set each path modifier 20 to the standby position St (step S8).

When the reference period H has not occurred (NO in step S5), the control computer C determines the presence of the weaving start signal (step S9). When the weaving start signal is inputted (YES in step S9), the control computer C proceeds to step S2.

Passing the trajectory modifier 20 from the standby position St to the braking position of the weft wire Br and to change the trajectory modifier 20 from the standby position St to the pulling position back. of weft thread Pu are made during a normal setting for weaving. Steps S6 and S7 are protection settings in which the trajectory modifier 20 is reciprocated in a span (angle of rotation span Θ) that is greater than the span (span of rotation angles Θ1 , Θ2) during normal setting. The protection setting can be implemented either during the weaving in which the two weft yarns Ya and Yb are used or in a weave in which a single weft yarn Ya or Yb is used.

The control computer C is a controller having a function a function, in the case of a normal setting, to adjust the operating position of the stepping motor Ma, Mb so that the position of the modifier of the trajectory 20 becomes modifies to change the trajectory of the weft yarn, and a function, in the protective setting frame, to subject the path modifier to reciprocating movement such that the span of the position change of the trajectory modifier 20 is greater than the span of the change of position of the modifier of the trajectory 20 during normal adjustment.

The embodiment as described above offers the advantageous effects indicated below.

When the setting is normal and inactive, the protection setting for subjecting the path modifier to reciprocating movement such that the span of the position modifier of the trajectory modifier 20 is greater (i.e. the extent to which the bearing balls 293 of the radial bearing 29 effect one or more revolutions) to the span of the change of position of the path modifier 20 during normal adjustment. Thus, grease spreads over the entire surface of the rolling elements or ball bearings 293 of the radial bearings 29 in the stepper motors Ma and Mb. Thus, the life of the bearings 29 is prolonged.

The protection setting is implemented when the weaving is stopped, the stop in question being accompanied by phenomena of insertion malfunctions of the weft thread or breakage of the warp thread. When the weaving is stopped, there is sufficient time for the protection setting, so that this configuration is advantageous to ensure spreading of the grease over the entire surface of the ball bearings 293.

Once the grease spreads over the entire surface of the ball bearings 293 of each bearing 29, the lubrication of the bearing 29 remains in good condition for an extended period of time. Thus, by setting a reference period H for example to about 10 hours, it is possible to maintain a good state of the bearings 29.

The protection setting is implemented after placing the trajectory modifier 20 in the initial position Ge at which the rotational position (operational position) of the stepping motor Ma, Mb can be identified. This means that the protection setting is implemented once the control computer C confirms that the trajectory modifier 20 is in its initial position Ge. Therefore, at the time of the protection setting, the path modifier 20 will not be located at an undesirable location i.e. where the weft son Ya and Yb leave the main nozzles 14A and 14B.

Setting to subject the trajectory modifier 20 to reciprocating movement between the initial position Ge and the lubrication position Ju eliminates the control to identify the position of the trajectory modifier 20 again at the beginning of the weave.

The setting to set the trajectory modifier 20 in the standby position St after the protection setting is advantageous in that the weft yarn is braked faster after the weaving restart.

In the case of an unused weft yarn braking device, it may happen that the trajectory modifier 20 of such weft yarn braking device moves freely. This movement may give rise to a malfunction such as contacting the trajectory modifier 20 with the weft yarn. However, in this embodiment, the path modifier 20 for an unused weft yarn braking device is always maintained in its standby position when the loom is put into operation. Thus, the free movement of the trajectory modifier 20 is prevented.

It is understood that the invention can be implemented in the embodiments shown below.

The trajectory modifier 20 may be reciprocated repeatedly during the protection setting.

The span of one or rotation of the trajectory modifier 20 in the protection setting may represent the span extending between the standby position St and the lubrication position Ju.

The protection setting can be performed each time the weaving stops.

The present invention is applicable to a weft yarn path modifying device which brakes on a single weft yarn.

A servomotor can be used as an actuator including an encoder whose position is adjustable. A rotary solenoid can also be used as an actuator including an encoder whose position is adjustable.

The present invention is applicable to a shareholder in which an output shaft is supported by a bearing having rollers for acting as rolling elements.

The weft braking device can be separated from the tandem nozzle. For example, the weft braking device can be positioned between the tandem nozzle and the weft length measuring storage device or between the tandem nozzle and the main nozzle.

The present invention is applicable to a weft-return weft-pulling apparatus having a single back-tensioning function of the weft yarn by pulling back the weft yarn to remove the distal end of the weft yarn in the weft yarn. main nozzle.

The present invention is applicable to a weft yarn path modification device, in which a rotary shaft to which a trajectory modifier is attached, is rotatably supported by a bearing, the rotary shaft being rotation using a linear shareholder. However, in this case, a conversion mechanism for converting the linear alternative motion of the linear shareholder into a rotational motion of the rotating shaft is required.

The present invention is applicable to a jet loom without a tandem nozzle.

Claims (6)

Apparatus for adjusting the insertion of the weft thread for a jet loom, comprising a device for modifying the path of the weft thread and a controller (C), wherein the device for modifying the trajectory of the thread weft yarn includes a path modifier (20) for changing the path of a weft yarn and an actuator for driving the path modifier (20), the controller (C) controlling the operating position of the actuator, characterized in that the controller (C) includes a function, in the case of a normal setting, for adjusting the operational position of the actuator such that the position of the path modifier (20) is modified to change the path of the weft yarn (Ya, Yb, and a function, in the case of a protection setting, for subjecting the modifier (20) of the trajectory to an alternating movement so that the span (Θ) of the change of position of the modifi The controller (20) of the trajectory becomes greater than the span (01, 02) of the change of position of the path modifier (20) during normal adjustment, the protection setting being implemented when the normal setting is inactive. 2. Apparatus for adjusting the insertion of the weft yarn in a jet loom according to claim 1, characterized in that the controller (C) implements the protection setting during a period during which the weaving is stopped. An apparatus for adjusting the insertion of the weft yarn in a jet loom according to claim 2, characterized in that the controller (C) implements the protection adjustment when stopping the weaving takes place after the course of a predetermined reference period of time when the power supply of the controller (C) is open or from the moment corresponding to the end of the previous protection setting. 4. Apparatus for adjusting the insertion of the weft yarn in a jet loom according to any one of claims 1 to 3, characterized in that the actuator is a rotary actuator (Ma, Mb) including an encoder , the position of the rotary actuator (Ma, Mb) being adjustable, inwhich the path modifier (20) is fixed to an output shaft (28) of the rotary actuator (Ma, Mb) into which controller ( C) implements the protection setting after placing the trajectory modifier (20) in its initial position in which the operational position of the rotary actuator (Ma, Mb) can be identified. Apparatus for adjusting the insertion of the weft yarn in a jet loom according to any one of claims 1 to 4, characterized in that the controller (C) places the modifier (20) of the trajectory in a waiting position when the normal setting is inactive and returns the modifier (20) of the trajectory to its waiting position after the implementation of the protection setting. Apparatus for adjusting the insertion of the weft yarn in a jet loom according to one of claims 1 to 5, characterized in that the span (Θ) of the rotation angle of the modifier ( 20) of the path during the protection setting represents the span in which a rolling element (293) makes one or more rotations.