JP7141240B2 - Electromagnetic device for loom to stop weft yarn in weft feeder and slider for that device - Google Patents

Description

The present invention relates to an electromagnetic device for weaving machines for stopping weft threads in a weft thread feeder, and to a slider for such a device. In particular, the stop device of the present invention is specifically designed for weft feeders used in air-jet looms and water-jet looms, where high frequency weft insertion is required under particularly harsh working environments. and to address the problem of dust contamination, which is always present at a high rate in textile environments.

As is well known, a weft feeder is a weft supply device which, during the operation of weft insertion, continuously stores the weft yarn in a drum by drawing the weft yarn axially, creating a ready-to-use weft yarn reserve. . The electromagnetic weft stop device of the present invention is located at the outlet side of said weft feeder and stops the weft thread from the drum as soon as the desired amount of weft thread (measured by the number of turns coming out of the drum) has been drawn by the weft feeder. and permanently blocks the unwinding of the weft from the drum during the completion of the operation of inserting the weft along the shed and the subsequent closing of the shed.

Said stopping device usually comprises an electromagnetic coil which controls the movement of the slider, the free end of which, when passed through the surface of the drum on which the thread is wound, engages itself in the corresponding hole. to prevent unwinding of other turns from the drum itself. The electromagnetic coils used in this type of device therefore provide a bi-stable state of the slider, i.e. the slider is in the retracted state while the weft is fed and in the forward position while the weft is fed. is controllable between a position where the is locked to the weft feeder drum.

In order to ensure adequate wear resistance and at the same time avoid deterioration of the weft yarns, it is known to provide the free ends of the slider, hereinafter referred to as end pieces, of a suitable ceramic material. Naturally, the slider must also comprise a core of ferromagnetic material sensitive to the magnetic field produced by the coil, where the bond between these two different materials is a thermoset plastic material. is performed by a matrix of Specifically, the slider of the currently known device is obtained by a molding process of said thermosetting plastic material in the molten state, wherein the ceramic material end piece and the ferromagnetic core are pre-placed in the mold as inserts. and then bonded together by a solidified plastic matrix.

A typical configuration of a known slider Cn of this type is shown in FIG. In FIG. 2, a cylindrical bush-shaped ferromagnetic core F at the central periphery of the slider Cn and a ceramic material end piece P at the first end of the slider Cn, having a substantially cylindrical (columnar) shape. and an end piece extending axially within the central portion of the aforementioned slider and comprising a series of annular grooves or recesses facilitating adhesion of the plastics material matrix M inside the core F; extending axially in the direction opposite the end piece P from the portion where the plastic material matrix M occupies the intermediate annular space between the ferromagnetic core F and the end piece P, the second The plastics material matrix M forming the ends can be clearly identified. The use of a plastic material for the matrix M also has the aim of making the slider Cn as light as possible and reducing the inertia of the slider Cn, thus enabling its use also in weaving machines with high weft insertions. have.

The slider is accommodated in a cylindrical guide bush made of plastic material and axially arranged inside the coil case, and the above-mentioned movement is carried out between the ferromagnetic core F of the slider Cn and the cylindrical guide bush. have the minimum clearance required to

Known weft stop devices using sliders Cn of the type described above have some typical drawbacks which are closely related to their construction and use characteristics, which are briefly explained.

A first drawback relates to the wear experienced by the cylindrical guide bushing of the slider. In this regard, the slider is only subject to the attractive/repulsive forces exerted by the magnetic field created by the coils as it moves in the reciprocating (alternating) path of the slider controlled by the coils, which is the force of attraction/repulsion of the slider. Note that having central symmetry about the axis, the attraction/repulsion forces themselves keep the slider perfectly centered within the slider's guide bushing. However, if the end piece P of the slider performs the function of stopping the weft yarn, the end piece P will not be affected by the weft yarn that a suddenly blocked weft yarn exerts on the end piece P when the weft yarn is pulled all the way across the shed. Directional forces are also experienced. Although this force is relatively small, the high arm existing between the point of action, i.e. the free end of the end piece, and the point of reaction, i.e. the contact area between the core F and each guide bush, causes the above-mentioned The forces exerted on the guide bush are sufficiently great to cause gradual wear of the guide bush wall. This causes a gradual misalignment of the motion of the slider with respect to the theoretical axial line of motion and, inter alia, the formation of plastic material dust, which progressively contaminates the end pieces and finally on the weft yarns. be transferred, causing contamination of the weft and thus the possibility of fabric defects.

A second drawback of conventional stopping devices is their relatively short service life, especially in heavy equipment (large) applications. The gradual misalignment of the slider Cn is also due to the inherent fragility of the ceramic material of the end piece with respect to bending stress, so that the end force effect by non-axial components with non-negligible substance during weft stop is negligible. It causes the end piece to break with a certain frequency when the piece is hit.

A third drawback, which shortens the service life of the device, is finally linked to the special assembly system of the known sliders, via the plastic material matrix M, which apparently consists of the matrices M integral with each other. It has much lower mechanical resistance properties than both of the ferromagnetic materials and ceramic materials that make it hard. Thus, the end piece P is subjected to repeated impacts at each end stop of the reciprocating motion of the end piece P, and subsequently the plastic material component (volume) contained between the end piece P and the ferromagnetic core F is high. As it is subjected to shear stress, it progressively exhibits structural failure, resulting in a loss of rebound resilience of the plastics material components resulting in complete separation, followed by slippage of the end piece P from the surrounding plastics material matrix M, thus causing the device to It may become unusable.

SUMMARY OF THE INVENTION The problem underlying the present invention is therefore to provide an electromagnetic device for stopping weft yarns of the type described above, which has a significantly extended service life. Preferably, the service life should be readily predeterminable based on normal wear criteria. Because the service life cannot be determined by phenomena such as displacement of the slider Cn and structural failure of the plastic material matrix M, it is not possible to predict the rate of evolution of such phenomena towards eventual collapse (misalignment or failure). This is because it is extremely difficult.

To achieve this solution, a first object of the present invention is to improve the composite structure of the slider, particularly with regard to the spacing of the plastic material matrix M contained between the end piece P and the ferromagnetic core F. It is to be.

A second object of the present invention is also to improve the slider guide system so that the lateral forces exerted by the pulled weft threads, which cause gradual displacement of the slider due to wear of the slider's sliding guides, are more effectively reduced. It can also be offset by

It is a further object of the present invention, ultimately, to reduce the adverse effects of end stop impacts on the structural integrity of the slider, and to reduce dust formation to free up the space in which the slider guides are located. protection and further reducing the effects of wear on the slider guide itself.

This problem is solved and these objects are achieved by an electromagnetic device for stopping a weft thread in a weft thread feeder of a weaving machine having the features of claim 1 and by a slider having the features of claim 12. . Other preferred features of the electromagnetic device according to the invention are described in the dependent claims.

Further features and advantages of an electromagnetic device for stopping weft yarns in a weft yarn feeder according to the present invention will be more apparent from the following detailed description of preferred embodiments, given by way of non-limiting example only and illustrated in the accompanying drawings. will be clear.

1 is an axial section through an electromagnetic stopping device according to the invention, with the slider for stopping the weft thread in the advanced position; FIG. 1 is a side, partially cross-sectional view of a known type of slider (prior art); FIG. 1 is a side, partial cross-sectional view of a slider in accordance with the present invention; FIG. 2 is a perspective view of the electromagnetic stop of FIG. 1, with parts separated; FIG.

According to the invention, in order to solve the problem highlighted above in a compact and particularly effective solution, the composite construction of the slider of the electromagnetic stop is fundamentally modified, comprising an end piece of ceramic material and a ferromagnetic core. Eliminates the use of a thermoset plastic material matrix as a connecting element between and modifies the guide system of similar sliders.

As clearly shown in FIGS. 1 and 3, the slider C of the weft stop device according to the invention consists of a ceramic material end piece 1 which has a cylindrical shape (cylindrical shape) over its extension. A ceramic material suitable for this application must have high hardness mechanical properties to adequately resist friction-induced wear during the weft stop phase, and also reduce friction with the guides during slider operation, It should have a high surface smoothness to avoid weft damage during the weft stop operation.

The end piece 1 is coupled to a corresponding axial cylindrical cavity 2c of an aluminum cylindrical intermediate element 2, said aluminum cylindrical intermediate element 2 having an appendage 2a, said appendage 2a facing said end piece 1, preferably has a cylindrical shape. Outside the aluminum intermediate element 2 there is a bush-shaped ferromagnetic core 3 which, as is evident from FIG. It comprises a cylindrical inner wall and an outer wall having a shape substantially similar to a single-leaf hyperboloid, varying to a maximum value at two opposite ends.

The bond between the ceramic material end piece 1 and the cavity 2c of the aluminum intermediate element 2 is preferably a mechanical interference bond via a press which provides absolute bond stability even after long periods of use. In order to avoid an increase in air pressure inside the cavity 2c, which can prevent complete bonding during the bonding step, a transverse hole is provided at the bottom of the cavity 2c to connect the cavity 2c to the outside.

Similarly, the bond between the aluminum intermediate element 2 and the bush-like core 3 is preferably a mechanical interference bond in any known manner, for example via cold pressing or pressing with hot core 3. done. Other types of bonding, such as adhesive or resin bonding, may not be preferred from the standpoint of lower resistance over time compared to the repeated impact loads that occur at each of the end stops of slider C. is also clearly possible.

The greater weight of the aluminum intermediate element 2 in the slider C of the invention with respect to the plastic material matrix M of known types of sliders Cn is compensated by the hyperboloidal shape of the outer surface of the ferromagnetic core 3, said hyperboloidal shape of the intermediate element Reduce the weight of this element to the extent that it compensates for the greater weight of 2. This weight reduction of the ferromagnetic core 3 does not significantly reduce the magnetic efficiency of the system. This is important because the curvature of the outer surface of the core 3 still allows to have enough ferrous material in each part of the core 3, and each part of the core 3 has a proper interaction with the electromagnetic field. Because there is

A particular outer hyperboloid shape of the ferromagnetic core 3 is possible because, according to the invention, the guiding of the reciprocating axial movement of the slider C is no longer the ferromagnetic core 3, as in the case of the known slider Cn. This is due to the fact that it cannot be obtained by using a sliding contact between the outer surface of 3 and a corresponding cylindrical bushing housed inside the coil case. In fact, in order to guide the reciprocating motion of the slider C, the present invention provides two opposing sliders cooperating in sliding contact with the cylindrical (cylindrical) appendages 2a of the end piece 1 and the intermediate element 2, respectively. A bush 4 is provided. The bushings 4 are housed in corresponding seats 5 formed in opposite flat walls of a case 6 in which the coil B is housed, in which case the coil B is, as mentioned above, mounted on the slider C in a manner known per se. controls the reciprocating motion of the The bushing 4 is preferably made of a material with low friction properties and high wear resistance properties, such as a ceramic material. Alternatively, plastic materials exhibiting mechanical properties similar to those described above may be used, for example polyethers, which have the advantage of lower cost compared to the ceramic materials conventionally used for such applications. Ether ketone (PEEK) based materials may also be used. In a preferred embodiment, the bushes 4 in contact with the end pieces 1 intended to support to a high degree the lateral forces exerted by the weft threads during the stopping phase are made of ceramic material, while the aluminum intermediate elements 2 The bushing 4 in contact with the appendage 2a is made of a plastic material having mechanical properties similar to those of PEEK-based materials.

During use of the device, the slider C moves the channel 7 axially between the coils B and inside the case 6 containing the coils B to the outer wall of the seat 5 of the bushing 4 mentioned above. Alternately (oscillates) between end stop positions established by striking the center body of slider C against . In order to dampen the alternating impacts of the slider C at said end stop positions, inside the channel 7 and on the seat 5 there is provided a damping washer 8 made of a suitable dampening material which does not shatter upon repeated impacts.

The free end of the appendage 2a is provided in a manner known per se with a conical wire spring M, the apex of which is attached to the final taper of the appendage 2a and the base of which is the outer container of the device. 11 (the spring M is only partially shown in the drawing for greater clarity), which is placed in a special seat formed in the cover 10 of 11 . The function of the spring M is to keep the end piece 1 pushed into the forward position, i.e. the weft stop position, in the event of a power shortage, in this case preventing an uncontrolled weft exit from the weft feeder. During normal operation of the slider C, the base of the spring rests on the wear bowl 9 with varying forces, so that the surface of the wear bowl 9 wears gradually and evenly. This is due to the fact that the unpredictable motion of the weft threads and the electromagnetic field can and does cause the entire slider C to rotate continuously, but is in fact not limited to this type of motion. A preferred material for the construction of bowl 9 is the PEEK-based material already mentioned above in relation to bushing 4, or a plastic material with similar mechanical properties.

As an alternative to the connection between the spring M and the bowl 9, which has the drawback of requiring periodic replacement of the bowl 9 and the formation of wear material inside the device, according to the invention, permanent magnets are It is provided at a position suitable for maintaining the slider C in the forward position, i.e. the weft stop position, when the coil B is not energized due to lack of power. In a preferred embodiment, said permanent magnet maintains the slider C in the advanced position shown in FIG. 1 in the event of power failure, while attraction to the appendage 2a is provided by a fixed case 6 made of ferrous material. , is accommodated at the free end of the appendage 2a of the intermediate element 2. As shown in FIG.

To contain the dust passage inside the device, the outer envelope of the device consists of a cup container 11 having a generally cylindrical shape, a cover 10 closing the mouth of the cup container 11, and located opposite the cover 10, the cup container 11 and a first O-ring sealing gasket 12 which is housed in a special peripheral circular seat. Advantageously, as is apparent from the exploded view of FIG. 4, a second inner gasket 12c is joined to gasket 12, the function of gasket 12c being to maintain the case 6 of coil B in the correct position and reduce assembly slack. It is to compensate for (looseness due to assembly). The second inner gasket 12c has a C-shape that allows for an exit for the power cable of the electronic device and allows for a greater thickness with respect to the gasket 12 . Thanks to the mutual bonding between the gaskets 12 and 12c, as soon as the first O-ring sealing gasket 12 is placed in the circular seat of the O-ring sealing gasket 12, the inner gasket 12c is automatically and immediately attached to the inner gasket 12c. It is worth mentioning that the .

The cup container 11 apparently comprises a central opening allowing passage of the end piece 1, which opening is internally protected by a dust-proof washer 13 which seals against the outer surface of the end piece 1.

This invention, however, is not to be construed as limited by the particular constructions which merely represent exemplary embodiments of the invention illustrated above, and that various modifications are possible, all of which include: It will be understood that any deviation from the scope of the invention is within the reach of those skilled in the art and is defined solely by the claims.

Claims (13)

An electromagnetic device for stopping a weft yarn in a weft yarn feeder of a loom, comprising:
a slider (C) that moves along a rectilinear path between two end stop positions in response to actuation of an electromagnetic coil (B) contained within a case (6);
A bush-shaped ferromagnetic core (3), a cylindrical ceramic end piece (1) for stopping the weft thread protruding from one side of the bush-shaped ferromagnetic core (3), the bush-shaped ferromagnetic core (3) and the an intermediate element (2) forming a mechanical connection with a ceramic end piece (1), comprising:
Said intermediate element (2) is a cylindrical aluminum element fixed within a cylindrical inner cavity of said bush-like ferromagnetic core (3) via a mechanical interference coupling, and said cylindrical aluminum element is axial further comprising an axial cylindrical inner cavity (2c) in which said ceramic end piece (1) is fixed via a mechanical interference coupling ,
Said slider (C) is guided by two opposing bushings (4) for reciprocating linear motion of said slider, within said two opposing bushings said ceramic end piece (1) and said cylindrical An electromagnetic device , wherein said ceramic end piece (1) and a cylindrical appendage (2a) projecting in the opposite direction respectively slide from a shaped aluminum element (2) .

2. Electromagnetic device for stopping weft threads in a weft thread feeder of a weaving machine according to claim 1 , wherein said bushes (4) are housed in corresponding seats (5) formed in said case (6). 3. Electromagnetic device for stopping weft threads in a weft thread feeder of a loom according to claim 2 , wherein said bushing (4) is made of a high performance plastic material such as a ceramic material or a PEEK based material. The outer surface of the bush-shaped ferromagnetic core (3) has a single-leaf hyperboloid shape, and the wall thickness of the bush-shaped ferromagnetic core (3) is two opposite from the minimum in the central region of the bush-shaped ferromagnetic core. 2. An electromagnetic device for stopping a weft thread in a weft thread feeder of a weaving machine according to claim 1, varying up to a maximum value at the end of said bush-like ferromagnetic core. Said end stop position of said slider (C) is determined by said bush-like ferromagnetic core (3) striking against the outer wall of said sheet (5) of said bush (4) and said Electromagnetic device for stopping weft yarns in a weft yarn feeder according to claim 2 , further comprising a braking washer (8) arranged above the outer wall . Said device is housed in a cup vessel (11) having a substantially cylindrical shape, the mouth of said cup vessel being closed by a cover (10) and a first O-ring opposite said cover (10). 2. An electromagnetic device for stopping weft threads in a weft thread feeder of a loom according to claim 1, wherein a sealing gasket (12) is accommodated in a suitable peripheral circular seat of said cup vessel (11). Acting on the free end of said appendage (2a) of said cylindrical aluminum element (2), keeping said slider (C) pushed out to said end stop position where said weft thread stops in case of power shortage. The base of said spring (M) rests on a wear bowl made of a high performance plastic material such as a PEEK-based material, said wear bowl being attached to said cover ( 10) An electromagnetic device for stopping weft threads in a weft thread feeder of a weaving machine according to claim 6 , contained in each sheet formed in 10). further comprising a permanent magnet, said permanent magnet adapted to hold said slider (C) in an extruded state in said end stop position where said weft yarn is stopped in the event of power shortage; Electromagnetic device for stopping the weft yarn in a weft yarn feeder of a weaving machine according to claim 6 , housed in the end of the appendage (2a) of 2). A second inner gasket (12c) is joined to said first O-ring sealing gasket (12), said second inner gasket (12c) holding said case (6) in place while compensating for assembly slack. 8. An electromagnetic device for stopping a weft thread in a weft thread feeder of a weaving machine as claimed in claim 7, which holds. The cup container (11) has a central opening through which the ceramic end piece (1) penetrates to the outside, and the inside of the central opening is dust-proof and sealed against the outer surface of the ceramic end piece (1). Electromagnetic device for stopping weft threads in a weft thread feeder of a weaving machine according to claim 6 , protected by a washer (13). A ferromagnetic bush-shaped core (3), a cylindrical ceramic end piece (1) for stopping a weft protruding from one side of said ferromagnetic bush-shaped core (3) at an end stop position, and said bush-shaped ferromagnetic core A slider for an electromagnetic device for stopping a weft thread in a weft thread feeder of a loom of the type consisting of (3) and an intermediate element (2) forming a mechanical connection between said ceramic end piece (1),
Said intermediate element (2) is a cylindrical aluminum element fixed within a cylindrical inner cavity of said bush-like ferromagnetic core (3) via a mechanical interference coupling, said cylindrical aluminum element being axially A slider, further comprising a cylindrical inner cavity (2c), in which said ceramic end piece (1) is fixed via a mechanical interference coupling in said axial cylindrical inner cavity. The outer surface of the bush-shaped ferromagnetic core (3) has a single-leaf hyperboloid shape, and the wall thickness of the ferromagnetic core (3) is two opposite said 12. A slider for an electromagnetic device for stopping a weft thread in a weft thread feeder of a weaving machine according to claim 11 , varying up to a maximum value at the end of the bush-like ferromagnetic core. said cylindrical aluminum element further comprising a permanent magnet, said permanent magnet keeping said slider (C) in an extruded state in said end stop position where said weft yarn is stopped in the event of power shortage; 13. A slider for an electromagnetic device for stopping a weft thread in a weft thread feeder of a weaving machine according to claim 12 , housed in said end of the appendage (2a) of (2).

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