CN108866768B

CN108866768B - Electromagnetic device for stopping weft yarn in weft yarn feeder of weaving machine and slider for such device

Info

Publication number: CN108866768B
Application number: CN201810450138.XA
Authority: CN
Inventors: 雷纳托·科莫托; 恩佐·丹多罗; 马泰奥·法扎里
Original assignee: Roj Srl
Current assignee: Roj Srl
Priority date: 2017-05-12
Filing date: 2018-05-11
Publication date: 2021-01-05
Anticipated expiration: 2038-05-11
Also published as: JP2019009422A; EP3401426B1; EP3401426A1; IT201700051526A1; TW201900958A; JP7141240B2; CN108866768A

Abstract

An electromagnetic device for stopping a weft yarn in a weft feeder of a weaving machine, the electromagnetic device comprising: a slider (C) adapted to move along an alternate rectilinear path between two end stop positions in response to the activation of an electromagnetic coil (B) housed in a casing (6) and consisting of a bushing-shaped ferromagnetic core (3), a cylindrical end piece (1) for blocking the weft yarn from protruding from one side of said ferromagnetic core (3) and an intermediate element (2) forming a mechanical connection between said ferromagnetic core (3) and said end piece (1). The intermediate element (2) is a cylindrical aluminium element, fastened by interference mechanical coupling in a cylindrical internal cavity of the bushing-shaped ferromagnetic core (3), and is also provided with an axial cylindrical internal cavity (2c) in which the end piece (1) is fastened by interference mechanical coupling.

Description

Electromagnetic device for stopping weft yarn in weft yarn feeder of weaving machine and slider for such device

Technical Field

The present invention relates to an electromagnetic device for stopping a weft yarn in a weft feeder of a weaving machine and to a slider for such a device. In particular, the stop device of the invention is specially designed for weft feeders used in air-jet and water-jet looms, and is designed both for the high-frequency insertion of the weft yarn and for the dust pollution under particularly severe environmental working conditions, in which dust is always present in high ratios.

Background

As is known, a weft feeder is a weft feeding device that continuously accumulates weft yarn in successive turns on a drum to produce a reserve of weft yarn during the operation of weft insertion that is easily obtained by extraction in the axial direction. The electromagnetic weft yarn stop device of the invention is located at the outlet side of the weft yarn feeder in order to prevent the unwinding of the weft yarn from the drum as soon as the desired amount of weft yarn (measured by the number of turns leaving the drum) has been pulled by the weft yarn feeder and to keep the unwinding of the weft yarn from the drum prevented all the time during the insertion of the weft yarn along the shed and the subsequent completion of the operation of closing the shed.

The above-mentioned stop means generally comprise an electromagnetic coil controlling the movement of the slider, the free end of which prevents the unwinding of the other turns from the drum itself, when the slider is threaded through the surface of the drum on which the weft yarn is wound, by inserting itself in the corresponding hole. The electromagnetic coil used in this type of device is therefore apt to provide a bistable state of the slider, i.e. the slider is controllable between a retracted state, in which the weft thread is fed, and a forward position, in which the weft thread is kept locked on the drum of the weft feeder.

In order to ensure sufficient wear resistance and at the same time avoid degradation of the weft yarn, it is known to provide the free end of the slider (hereinafter also referred to as end piece) with a suitable ceramic material. Naturally, the slider must also comprise a core of ferromagnetic material sensitive to the magnetic field formed by the coil, and the coupling between these two different materials is now performed by a matrix of thermosetting plastic material; in particular, the sliders of the devices known so far are obtained by a moulding process of said thermosetting plastic material in the molten state, in which the ceramic end piece and the ferromagnetic core are previously placed in a mould as an insert and then mutually integrated by a solidified plastic matrix.

A standard construction of a known slider Cn of this type is shown in fig. 2, in which it is clearly recognizable that: a ferromagnetic core F in the shape of a cylindrical bush in a central peripheral portion of the slider Cn; an end piece P of ceramic material, as a first end of the slider Cn, having a substantially cylindrical shape and extending axially inside the core F inside the aforesaid central portion of the slider, inside the core F there being provided a series of annular grooves or recesses facilitating the adhesion of the matrix M of plastic material; a matrix M of plastic material extends axially from the central portion of the slider Cn, occupying the intermediate annular space between the ferromagnetic core F and the end piece P, in the opposite direction to the end piece P, so as to form the second end of the slider. The use of plastic material for the matrix M also has the purpose of lightening the slider Cn as much as possible, to reduce its inertia and thus allow its use in looms with high frequency weft insertion.

The aforesaid slider is housed inside a cylindrical guide bush made of plastic material and positioned axially inside the coil shell, with the minimum clearance necessary to allow said movement between the ferromagnetic core F of the slider Cn and the cylindrical guide bush.

Known weft yarn stopping devices using sliders Cn of the type described above have some typical drawbacks, which are closely linked to their constructional and use characteristics and will now be briefly explained.

A first drawback relates to the wear to which the cylindrical guide bushing of the slider is subjected. In this regard, it should be noted that when the slider travels in an alternating path controlled by the coil, the slider is only subjected to the attractive/repulsive forces exerted by the magnetic field formed by the coil, these forces having central symmetry with respect to the axis of the slider and, therefore, these forces themselves keep the slider completely centered within the guide bush of the slider. However, when the end piece P of the slider performs its function of blocking the weft thread, the slider is also subjected to a transverse force exerted on the slider by the suddenly blocked weft thread when the weft thread is fully stretched in the entire shed. Although this force is relatively low, the high arms present 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 the respective guide bush) result in a sufficiently high force being released onto said guide bush, in the weft stopping position, resulting in a progressive wear of the guide bush walls over time. This causes a progressive misalignment of the slider with respect to the movement of the theoretical axial operating line and, above all, the formation of dust of plastic material, which progressively contaminates the end pieces and eventually transfers to the weft thread, causing it to become dirty and causing possible defects on the fabric.

A second drawback of the conventional stop devices is the rather short service life in particularly heavy applications. Also due to the inherent fragility of the ceramic material of the end piece with respect to bending stresses, the progressive misalignment of the slider Cn may cause the end piece to break at a certain frequency when it is subjected to a force with a non-negligible substantial non-axial force component during the stoppage of the weft yarn.

A third drawback of reducing the service life of the device is finally linked to the particular assembly system of the known slider by the plastic material matrix M, which obviously has much lower mechanical resistance characteristics than the ferromagnetic and ceramic materials integral with each other by the matrix M. Thus, after the end piece P has undergone repeated impacts at each end stop of its alternating movement, the volume of plastic material comprised between the end piece P and the ferromagnetic core F is subjected to high shear stresses, thus developing structural failure, losing its elastic properties, until it causes the end piece P to completely separate from the surrounding plastic material matrix M and subsequently to slip, thus rendering the device unusable.

The problem underlying the present invention is therefore to provide an electromagnetic device of the above-mentioned type for stopping a weft thread, which has a significantly extended useful service life. Preferably, the useful service life should furthermore be able to be readily determined beforehand on the basis of normal wear criteria, since it is no longer determined by the phenomena-misalignment of the slider Cn and structural failure of the plastic material matrix M-the evolution speed of which towards eventual failure is very difficult to predict.

In order to solve this problem, a first object of the present invention is to improve the composite structure of the slider, in particular with respect to the space comprising the plastic material matrix M between the end piece P and the ferromagnetic core F.

A second object of the invention is also to improve the slider guide system to more effectively counteract the transverse forces exerted by the stretched weft thread, which transverse forces cause progressive misalignment of the slider due to wear of its sliding guides.

Other objects of the present invention are ultimately to reduce the negative impact of end stop collisions on the structural integrity of the slider and to reduce dust formation, thereby protecting the space in which the slider guide is located and further reducing the impact of wear on the slider guide itself.

Disclosure of Invention

This problem is solved and these objects are achieved by the electromagnetic device and the slider for stopping weft yarn in a weft feeder according to the present invention. The electromagnetic device and the slider for stopping the weft thread in the weft thread feeder are described below, as are other preferred features of the electromagnetic device of the invention.

An electromagnetic device for stopping a weft yarn in a weft feeder of a weaving machine comprises: a slider adapted to move along an alternating rectilinear path between two end stop positions in response to activation of an electromagnetic coil housed in a housing, and consisting of a bushing-shaped ferromagnetic core, a cylindrical end piece for blocking weft yarn from protruding from one side of said ferromagnetic core, and an intermediate element forming a mechanical connection between said ferromagnetic core and said end piece, wherein said intermediate element is a cylindrical aluminium element fastened by interference mechanical coupling in a cylindrical internal cavity of said bushing-shaped ferromagnetic core, and is further provided with an axial cylindrical internal cavity in which said end piece is fastened by interference mechanical coupling.

Optionally, the slider is guided in its alternating rectilinear motion by two opposite bushes, inside which the end piece and a cylindrical appendage projecting from the cylindrical aluminum element in the opposite direction to the end piece slide respectively.

Optionally, the bushing is housed in a corresponding seat formed in the housing.

Optionally, the bushing is made of a ceramic material or a high performance plastic material.

Optionally, the outer surface of the liner-shaped ferromagnetic core has a single-sheet hyperboloid shape, the wall thickness of the ferromagnetic core varying from a minimum value at a middle region thereof to a maximum value at two opposite ends thereof.

Optionally, an end stop position of the slider is determined by the ferromagnetic core striking an outer wall of a seat of the bushing, and a damping washer is further provided, the damping washer positioned above the striking outer wall of the seat.

Alternatively, the device is housed in a cup-shaped container having a substantially cylindrical shape, the mouth of which is closed by a lid, and a first O-ring sealing gasket opposite the lid is housed in a suitable peripheral circular seat of the cup-shaped container.

Optionally, the electromagnetic device is further provided with a conical wire spring acting on the free end of the appendage of the cylindrical aluminum element to keep the slider pushed in the forward position stopping the weft yarn in the event of a power shortage, and the base of the spring rests on a wear-resistant bowl made of high-performance plastic material, which is housed in a corresponding seat formed in the cover.

Optionally, the high performance plastic material is a PEEK family material.

Optionally, the electromagnetic device is further provided with a permanent magnet housed in the end of the appendage of the cylindrical aluminum element for keeping the slider in the forward position of stopping the weft yarn in the event of a power shortage.

Optionally, a second inner gasket is associated with said first O-ring sealing gasket, said second inner gasket being adapted to keep said housing in the correct position while compensating for its assembly play.

Optionally, the cup-shaped container has a central opening for the end piece to be open to the outside, the inside of the central opening being protected by a dust gasket providing a seal against the outer surface of the end piece.

A slider for an electromagnetic device for stopping a weft yarn in a weft feeder of a weaving machine, as described in the above embodiment, of the type consisting of a ferromagnetic core in the form of a bush, a cylindrical end piece for preventing a weft yarn from protruding from one side of the ferromagnetic core, and an intermediate element forming a mechanical connection between the ferromagnetic core and the end piece, wherein the intermediate element is a cylindrical aluminum element fastened by interference mechanical coupling inside a cylindrical internal cavity of the ferromagnetic core in the form of a bush, and also has an axial cylindrical internal cavity in which the end piece is fastened by interference mechanical coupling.

Optionally, the slider is further provided with a permanent magnet housed in the end of the cylindrical appendage of the cylindrical aluminum element projecting from the cylindrical aluminum element in the opposite direction to the end piece, for keeping the slider in the forward position of stopping the weft yarn in the event of a power shortage.

Drawings

Further features and advantages of the electromagnetic device for stopping weft yarns in a weft feeder according to the present invention will in any case become more apparent from the following detailed description of a preferred embodiment of the electromagnetic device, given purely by way of non-limiting example and illustrated in the accompanying drawings, in which:

fig. 1 is an axial cross-sectional view of an electromagnetic stopping device according to the invention, in which the slider is in a forward position for stopping the weft thread;

FIG. 2 is a side and partial cross-sectional view (prior art) of a slider of known type;

FIG. 3 is a side and partial cross-sectional view of a slider according to the present invention; and

fig. 4 is a perspective view of the electromagnetic stopping device of fig. 1 with parts exploded.

Detailed Description

According to the present invention, in order to solve the above highlighted problems in a concise and particularly effective solution, the composite structure of the slider of the electromagnetic stopping device has been drastically modified, abandoning the use of a matrix of thermosetting plastic material as the connecting element between the end piece of ceramic material and the ferromagnetic core, and modifying the same guiding system of the slider.

As clearly shown in fig. 1 and 3, the slider C of the weft stopping device according to the invention comprises an end piece 1 of ceramic material having a cylindrical shape over its entire extension. Suitable ceramic materials for this application must have mechanical properties of high hardness to sufficiently withstand the wear caused by friction during the stop of the weft thread and a high surface smoothness to reduce the friction with the guide during the movement of the slider and to avoid damaging the weft thread during the stop operation of the slider.

The end piece 1 is coupled in a corresponding axial cylindrical cavity 2c of an aluminium cylindrical intermediate element 2, the intermediate element 2 having an appendix 2a, the appendix 2a being opposite to the end piece 1 and preferably having a cylindrical shape. A liner-shaped ferromagnetic core 3 outside the aluminum intermediate element 2; as is clear from fig. 3, the ferromagnetic core 3 is provided with a cylindrical inner wall and an outer wall substantially shaped like a single-sheet hyperboloid, so that the wall thickness of the ferromagnetic core varies from a minimum value at its middle region to a maximum value at its two opposite ends.

The coupling between the ceramic end piece 1 and the cavity 2c of the aluminium intermediate element 2 is preferably an interference mechanical coupling by extrusion, which provides absolute coupling stability even over a long service life. To avoid an increase of the air pressure inside the cavity 2c, a transverse hole is provided at the bottom of the cavity 2c for connecting the cavity 2c to the outside, which would otherwise hinder the complete coupling during the coupling step.

Similarly, the coupling between the aluminium intermediate element 2 and the bushing-shaped core 3 is also preferably an interference mechanical coupling, obtained in cold conditions or in any known way (for example by extrusion) with the hot core 3. Other types of coupling, for example by means of adhesive or resin, are obviously possible even if they are not preferred, since their resistance becomes lower and lower over time, considering the repeated impact loads that occur at each end stop of the slider C.

The greater weight of the intermediate element 2 made of aluminum in the slider C of the invention with respect to the plastic material matrix F of the slider Cn of known type is compensated by the hyperboloid shape of the outer surface of the ferromagnetic core 3, which reduces the weight of the element to such an extent as to compensate for the greater weight of the intermediate element 2. This weight reduction of the ferromagnetic core 3 does not significantly reduce the magnetic efficiency of the system, as the curvature of the outer surface of the core 3 still allows for sufficient ferrous material in the portion of the core 3 where it is important to have sufficient interaction with the electromagnetic field.

A particular outer hyperboloid shape of the ferromagnetic core 3 is possible since, according to the invention, the guidance of the alternating axial movement of the slider C is no longer obtained by exploiting the sliding contact between the outer surface of the ferromagnetic core 3 and the corresponding cylindrical bush housed inside the coil shell, as is the case with the known slider Cn. In fact, in order to guide the reciprocating movement of the slider C, in the present invention two opposite bushes 4 are provided, apt to cooperate in sliding contact with the cylindrical appendix 2a of the end piece 1 and the intermediate element 2, respectively. The bush 4 is housed in a respective seat 5 formed in the opposite flat wall of the casing 6, and the coil B is housed in the casing 6, the coil B controlling the alternate movement of the slider C in a manner known per se, as described above. The bushing 4 is preferably made of a material having low friction and high wear resistance properties, such as a ceramic material. Alternatively, plastic materials having the same mechanical properties as noted above may be used, such as members of the Polyetheretherketone (PEEK) family, which has the advantage of being less costly than ceramic materials traditionally used for such applications. In a preferred embodiment, the bush 4 in contact with the end piece 1, which is made of ceramic material, is intended to support to a high degree the transverse forces exerted by the weft yarn during the stop phase, whereas the bush 4 in contact with the appendix 2a of the aluminium intermediate element 2 is made of plastic material having similar mechanical characteristics to those of members of the PEEK family.

During use of the device, the slider C is moved alternately inside the channel 7, between end stop positions, the channel 7 being arranged axially between the coils B and inside the housing 6 containing the coils B, the end stop positions being determined by the central body of the slider C striking the outer wall of the seat 5 of the above-mentioned bush 4. In order to damp the alternating impacts of the slider C at said end stop positions, a damping washer 8 made of a suitable shock-absorbing material is provided in the channel 7 and on the seat 5, which does not shatter due to repeated impacts.

At the free end of the accessory 2a, in a manner known per se, a conical wire spring M is provided, the apex of which fits into the last tapered portion of the accessory 2a and the base of which rests on a wear-resistant bowl 9, the bowl 9 being positioned in a dedicated seat formed in a lid 10 of an outer container 11 of the device (in the figures, the spring M is only partially shown for greater clarity). The function of the spring M is to keep the end piece 1 pressed in the forward position, i.e. the weft yarn stop position, in case of a power shortage, to prevent uncontrolled outflow of weft yarn from the weft feeder in this case. During normal movement of the slider C, the spring base rests with varying force on the wear-resistant bowl 9, the surface of the wear-resistant bowl 9 being gradually and uniformly worn out due to the fact that the unpredictable action of the weft yarns and the electromagnetic field may (and indeed does) cause the entire slider C to rotate continuously, without in fact inhibiting such movement in any way. A preferred material for constructing the bowl 9 is a PEEK plastics material or a plastics material with similar mechanical properties as already described above in relation to the bushing 4.

As an alternative to the coupling between the spring M and the bowl 9, which has the disadvantage of requiring regular replacement of the bowl 9 and the formation of wear material within the device, according to the invention a permanent magnet is provided in a suitable position to keep the slider C in the forward position, i.e. the weft stop position, when the coil B is not energized due to a power shortage. In a preferred embodiment, said permanent magnet is fitted over the free end of appendix 2a of intermediate element 2, so as to provide an attraction force thereto in the event of a power shortage, by means of a fixed casing 6 made of ferrous material, in order to keep slider C in the forward position shown in fig. 1.

In order to prevent the entry of dust into the device, the housing of the device is formed by a cup-shaped container 11 having a substantially cylindrical shape and a lid 10 closing the mouth of the cup-shaped container 11, a first O-ring sealing gasket 12, opposite the lid 10, being housed in a special peripheral circular seat of the cup-shaped container 11. Advantageously, as clearly shown in the exploded view of fig. 4, a second inner spacer 12c is associated with the spacer 12, the function of the second inner spacer 12c being to keep the housing 6 of the coil B in the correct position, thus restoring the assembly play. The second inner pad 12C has a C-shape to allow removal of the power cable of the electronic device and has a greater thickness with respect to the pad 12; notably, thanks to their mutual engagement, the inner gasket 12c is automatically and easily put in its correct working position once the first O-ring sealing gasket 12 is positioned in its circular seat.

The cup-shaped container 11 is obviously provided with a central opening to allow the passage of the end piece 1 and this opening is internally protected by a dust gasket 13, the dust gasket 13 providing a seal against the outer surface of the end piece 1.

It is to be understood, however, that the invention is not to be considered limited to the particular arrangements shown above, which represent only exemplary embodiments of the invention, but that various modifications are possible within the purview of one skilled in the art without departing from the scope of the invention itself, which is limited only by the claims appended hereto.

Claims

1. An electromagnetic device for stopping a weft yarn in a weft feeder of a weaving machine, the electromagnetic device comprising: slider (C) adapted to move along an alternate rectilinear path between two end stop positions in response to the activation of an electromagnetic coil (B) housed in a casing (6) and consisting of a ferromagnetic core (3) of bushing shape, a cylindrical end piece (1) for blocking the weft yarn from protruding from one side of said ferromagnetic core (3) and an intermediate element (2) forming a mechanical connection between said ferromagnetic core (3) and said end piece (1), characterized in that said intermediate element (2) is a cylindrical aluminum element fastened by interference mechanical coupling in a cylindrical internal cavity of said ferromagnetic core (3) of bushing shape and is also provided with an axial cylindrical internal cavity (2C) in which said end piece (1) is fastened by interference mechanical coupling.

2. Electromagnetic device for stopping a weft yarn in a weft feeder of a weaving machine according to claim 1, wherein said slider (C) is guided in its alternating rectilinear motion by two opposite bushes (4), inside which bushes (4) said end piece (1) and a cylindrical appendix (2 a) projecting from said cylindrical aluminum element (2) in the opposite direction to said end piece (1) slide respectively.

3. Electromagnetic device for stopping a weft yarn in a weft feeder of a weaving machine according to claim 2, wherein said bushings (4) are housed in respective seats (5) formed in said housing (6).

4. Electromagnetic device for stopping a weft yarn in a weft feeder of a weaving machine according to claim 3, wherein said bush (4) is made of a ceramic material or a high-performance plastic material.

5. Electromagnetic device for stopping a weft yarn in a weft feeder of a weaving machine according to claim 1, wherein the outer surface of said liner-shaped ferromagnetic core (3) has the shape of a single-sheet hyperboloid, the wall thickness of said ferromagnetic core (3) varying from a minimum value at its middle area to a maximum value at its two opposite ends.

6. Electromagnetic device for stopping a weft yarn in a weft feeder of a weaving machine according to claim 1, wherein the end stop position of the slider (C) is determined by the ferromagnetic core (3) hitting the outer wall of the seat (5) of the bush (4) and a damping washer (8) is further provided, said damping washer (8) being positioned above said hitting outer wall of the seat (5).

7. Electromagnetic device for stopping a weft yarn in a weft feeder of a weaving machine according to claim 2, wherein said device is housed in a cup-shaped container (11) having a substantially cylindrical shape, the mouth of which is closed by a cover (10), and a first O-ring sealing gasket (12) opposite said cover (10) is housed in a suitable peripheral circular seat of said cup-shaped container (11).

8. Electromagnetic device for stopping the weft yarn in a weft feeder of a weaving machine according to claim 7, wherein a conical wire spring (M) is further provided, which acts on the free end of the appendage (2 a) of the cylindrical aluminium element (2) in order to keep the slider (C) pushed in the forward position stopping the weft yarn in the event of a power shortage, and the base of which rests on a wear-resistant bowl made of high-performance plastic material, which is housed in a corresponding seat formed in the cover (10).

9. Electromagnetic device for stopping a weft yarn in a weft feeder of a weaving machine according to claim 4 or 8, wherein said high-performance plastic material is a PEEK family material.

10. The electromagnetic device for stopping weft yarn in a weft feeder of a weaving machine according to claim 7, wherein a permanent magnet is further provided, housed in the end of the appendix (2 a) of the cylindrical aluminum element (2), for keeping the slider (C) in the forward position of stopping weft yarn in the event of a power shortage.

11. Electromagnetic device for stopping a weft yarn in a weft feeder of a weaving machine according to claim 7, wherein a second inner gasket (12 c) is associated with said first O-shaped sealing gasket (12), said second inner gasket (12) being adapted to keep said housing (6) in the correct position while compensating for its assembly play.

12. Electromagnetic device for stopping a weft yarn in a weft feeder of a weaving machine according to claim 7, wherein the cup-shaped container (11) has a central opening for the end piece (1) to the outside, the inside of the central opening being protected by a dust gasket (13) providing a seal against the outer surface of the end piece (1).

13. Slider for an electromagnetic device for stopping a weft yarn in a weft feeder of a weaving machine according to any one of the preceding claims, of the type consisting of a bushing-shaped ferromagnetic core (3), a cylindrical end piece (1) for preventing a weft yarn from protruding from one side of the ferromagnetic core (3), and an intermediate element (2) forming a mechanical connection between the ferromagnetic core (3) and the end piece (1), characterized in that the intermediate element (2) is a cylindrical aluminum element fastened by interference mechanical coupling inside a cylindrical internal cavity of the bushing-shaped ferromagnetic core (3), and also has an axial cylindrical internal cavity (2c) in which the end piece (1) is fastened by interference mechanical coupling.

14. Slider of an electromagnetic device for stopping a weft yarn in a weft feeder of a weaving machine according to claim 13, wherein the outer surface of the liner-shaped ferromagnetic core (3) has the shape of a single-sheet hyperboloid, the wall thickness of the ferromagnetic core (3) varying from a minimum value at its middle area to a maximum value at its two opposite ends.

15. Slider of an electromagnetic device for stopping a weft yarn in a weft feeder of a weaving machine according to claim 14, wherein a permanent magnet is further provided, housed in the end of the cylindrical appendix (2 a) of the cylindrical aluminum element (2) projecting from the cylindrical aluminum element (2) in the opposite direction to the end piece (1), for keeping the slider (C) in a forward position of stopping a weft yarn in case of power shortage.