EP1314805B1

EP1314805B1 - A method of weft braking when picking the weft through a shed of a pneumatic weaving machine and a braking jet

Info

Publication number: EP1314805B1
Application number: EP20020466001
Authority: EP
Inventors: Petr Karel; Jiri Mlynar; Josef Dvorak; Karel Adamek; Martin Beran
Original assignee: Vyzkumny Ustav Textilnich Stroju Liberec AS
Current assignee: Vyzkumny Ustav Textilnich Stroju Liberec AS
Priority date: 2001-10-19
Filing date: 2002-10-18
Publication date: 2007-05-23
Anticipated expiration: 2022-10-18
Also published as: EP1314805A2; EP1314805A3; DE60220236D1; CZ20013766A3; CZ298377B6; DE60220236T2

Description

Technical field

The invention relates to a method of weft braking when picking the weft through a shed of a pneumatic weaving machine in which the weft being picked through a direct pick channel of the reed is exposed to a braking force acting opposite the direction of the weft motion.
The invention also relates to a device for braking weft in the phase of the weft picking through a shed of a pneumatic weaving machine comprising on a swinging batten a reed with a direct pick channel.
The invention further relates to a braking jet for a weaving machine consisting of a hollow body adapted at its upper end for entering between warp threads and fitted in the region of its upper end with at least one pressure air outlet aperture situated substantially transversely to the longitudinal axis of the braking jet.

Background art

When passing through the shed of a pneumatic weaving machine or when being inserted into the shed, the weft exposed to the picking operations passes successively through three picking stages characterized by:

1) weft acceleration from zero to picking speed;
2) weft motion through the shed at picking speed, and
3) weft stop.

The weft stop is a dynamic process accompanied among others by impact effects (impact waves) that are together with the inertia forces function of not only the picking speed, picking interval, and material constants of the weft but also of the weft position as defined by the coordinates passing through the longitudinal axis of the weft. In practice, these effects result in lack of uniformity with which the deformations and changes in the weft volume due to the weft length are distributed along the weft length. These deformations and changes in the weft volume are biggest in the area of application of the weft braking force, for instance on the pin of the metering device, and they continuously diminish down to zero value at the free weft end. The quality of the weaving process is thus impaired not only by increased number of defects and weft ruptures but also by the uneven distribution of the weft volume along the cloth width sometimes resulting in optical and functional defects of the cloth being produced.
These unfavourable influences can be reduced by applying what is known as weft brake situated along the path of the weft to be picked between the weft metering device and the main jet of the pneumatic weaving machine. The weft brake, activated in the closing stage of the weft pick acts on the weft passing through friction surfaces of the weft brake by friction force absorbing the kinetic energy of the weft by friction in the weft brake and thus reducing the impact and force effects on the weft. As a rule, the application of the weft brake reduces the number of weft defects and ruptures but fails to remove the lack of uniformity of the weft deformation distribution, only reducing the deformation size.
A method of weft braking according to the preamble of claim 1 is known from JP-A-05 263336.
The invention intends both further to reduce the absolute size of the weft deformations and to achieve their uniform distribution along the weft length.

Principle of the invention

The goal of the invention has been reached by a method of weft braking when picking the weft through a shed of a pneumatic weaving machine whose principle consists in that the weft being picked is in the direct pick channel exposed to a force pressing it onto the wall of the direct pick channel and thus braking the weft, reducing the absolute size of the weft deformations and achieving their uniform distribution along the weft length.
From the point of view of suitable timing of the action on the weft in the direct pick channel it is advantageous if the weft is acted upon either simultaneously along the whole length of the direct picking channel or successively along the length of the direct picking channel. In the latter case, it is advantageous if the force acting on the weft begins to work at the beginning of the direct pick channel prior to the completion of the weft insertion into the direct pick channel.
To effectively bring the weft into contact with the wall of the direct pick channel, it is advantageous if the weft being picked through the direct pick channel is exposed to a streams of a pressure medium oriented either transversely to the direction of the weft motion through the direct pick channel or transversely to the respective wall of the direct pick channel and at least partly opposite the motion direction of the weft through the direct pick channel.
The principle of the device for braking weft in the phase of the weft picking through a shed of a pneumatic weaving machine consists in that the pneumatic weaving machine carries a number of braking jets coupled both with a source of a pressure medium and with a control device and having at least in the pick position of the reed their ends fitted with pressure medium outlet apertures situated opposite the opening of the direct pick channel, the outlet apertures of the pressure medium of the braking jets being in this position directed into the direct pick channel opposite the wall of the direct pick channel or in the direction opposite the respective wall of the direct pick channel and at least partly opposite the direction of the weft motion through the direct pick channel.
Each of these two embodiments of the device for braking on a pneumatic weaving machine is a highly efficient and reliable arrangement applicable both on newly built and on existing pneumatic weaving machines.
The principle of the braking jet for the weaving machine consists in that the pressure air outlet aperture is made as a diffusion outlet aperture.
Such a jet advantageously diffuses pressure air stream flowing against the direct pick channel so that it advantageously acts on a longer section of the weft being picked and thus reliably brings it into contact with the wall of the direct pick channel and reliably produces the braking force acting on the weft with all its positive consequences.
To obtain satisfactory results of the pressure air diffused by the braking jet it is advantageous if the braking jet has a cavity made as a channel consisting of cross sections continuously following each other, continuously diminishing in the direction from the lower end of the braking jet to the upper end of the braking jet, arranged one after another in a non-specifically curved bend and followed by the diffusion outlet aperture.
In one preferred embodiment, the cavity of the braking jet is at its lower section cylindrical, turns to a flattened arrangement in the middle section, and from it to a non-specifically curved bend.
This arrangement of the cavity of the braking jet permits advantageous creation of the braking jet body with cylindrical lower section advantageous for fixing the braking jet to the weaving machine, and with flattened upper part facilitating smooth insertion of the braking jet between warp threads. The arrangement is advantageous also from the point of view of the advantageous pressure air streaming through the cavity of the braking jet.
To improve the properties of the braking jet, in particular to reduce the negative influence of pressure air fluctuation in the braking jet on the parameters, especially the geometrical ones, of the outlet stream, it is advantageous if in the non-specifically curved bend of the cavity the wall of the braking jet cavity on the side near the diffusion outlet aperture is bulged out in the direction towards the longitudinal axis and joins the lower side of the diffusion outlet aperture while the wall of the braking jet cavity on the side remote from the diffusion outlet aperture is continuously curved to a shape ensuring that it successively comes near to the longitudinal axis of the braking jet, cuts the longitudinal axis of the braking jet, and joins the upper side of the diffusion outlet aperture.

Description of the drawings

The invention is schematically shown in the drawings in which Fig. 1 is an axonometric view of a part of a weaving machine with a batten, a reed, stationary relay-like arranged jets, and braking jets mounted stationary on the frame of the pneumatic weaving machine, Fig. 2 is an axonometric view of the batten of the pneumatic weaving machine with a combined stationary system of relay-like arranged jets and of braking jets, Fig. 3 an example of embodiment of a pneumatic weaving machine with braking jets, Fig. 4a longitudinal sectional-view of the braking jet Fig. 4b longitudinal sectional view of the braking jet from Fig 4 and the plane passing through the outlet aperture , Fig. 4c sectional view A-A from Fig. 4 b, point Fig. 4d a sectional view B-B from Fig. 4b, and Fig. 4e a sectional view C-C from Fig. 4b

Specific description

The method of weft braking when picking the weft through a shed of a pneumatic weaving machine and the device for carrying out the method will be described on a pneumatic weaving machine with stationary, i.e., during the weaving machine operation immovable, relay-like arranged jets.
The pneumatic weaving machine comprises a frame 15 carrying a batten 1 mounted swingingly and holding a reed 2 fixed to it and comprising a direct pick channel 3 . Suitably related to the entry of a weft 13 into the direct pick channel 3 , in Fig. 1 from the left side of the reed 2 , are not shown devices for preparing the weft 13 for picking such as a weft thread container, weft metering device, etc., and at least one main jet charged with the picking of the weft 13 through the shed at a picking speed v . The shed is produced by separating warp threads by means of a suitable shed mechanism onto a lower and an upper part 10 , 11 of the shed by means of a system of not represented healdframes with healds 12 with heald eyes 120 for guiding individually warp threads.
Opposite an opening 30 of the direct pick channel 3 and along the (length of the) reed 2 at least in the picking position of the reed 2 there are situated ends of relay-like arranged jets 5 supporting by their operation the picking of the weft 13 through the shed and having their pressure air outlet apertures oriented obliquely in the direction A into the direct pick channel 3 in the direction of the picking of the weft 13 through the direct pick channel 3. The relay-like arranged jets 5 are connected to a not represented pressure air source, and their operation is controlled by a not represented control device. In the shown examples of embodiment, the relay-like arranged jets 5 are relative to the reed 2 during the weaving stationary mounted on a support means 6 which is in its turn immovably mounted on the batten 1 of the weaving machine. In a not shown example of embodiment, the relay-like arranged jets 5 are during the weaving operation suitably adjustable in relation to the reed 2 and their pressure air outlet apertures are in the interval of the weft 13 picking through the shed in front of the opening 30 of the direct pick channel 3 obliquely in the direction A into the direct pick channel 3 in the direction of the weft 13 picking through the direct pick channel 3 . At the moment of the beat-up of the weft 13 into the front 17 of the cloth in formation, the ends of the relay-like arranged jets 5 with their pressure air outlet apertures are situated outside the area of the opening 30 of the direct pick channel 3 of the reed 2 .
The weaving machine is equipped with a number of braking jets 9 for the weft 13 situated in the direct pick channel 3 . The ends of the braking jets 13 fitted with pressure air outlet apertures are situated opposite the opening 30 of the direct pick channel 3 and their pressure air outlet apertures are directed in the direction B obliquely to the picking direction of the weft 13 through the direct pick channel 3 in the direction against the bottom 4 of the direct pick channel 3 or are directed into the direct pick channel at least slightly opposite the direction of the weft 13 pick through the direct pick channel 3 . The pressure air outlet stream 14 coming from the braking jets 9 acts on the weft 13 in process of picking on the surface of its longitudinal cross section defined by the transverse dimension of the weft 13 and by the length of the weft 13 . The braking jets 9 are coupled with a not represented pressure air source and with a not represented control device adapted to control their operation. In the example of embodiment shown in Fig. 1, the braking jets 9 are mounted on an auxiliary support means 7 made as a part of the frame 15 of the pneumatic weaving machine and are during the weaving operation immovable in relation to the reed 2 . In the example of embodiment shown in Fig. 2, the braking jets 9 are seated on the batten 1 of the pneumatic weaving machine in alternation with the relay-like arranged jets 5 on the common support means 6 and are during the weaving process immovable in relation to the reed 2.
In a not represented example of embodiment, the braking jets 9 are free to move in relation to the reed 2 during the weaving, for instance by being mounted on a suitable moving support means coupled with a suitable drive. The operation of the support means is suitably controlled.
In another non shown example of embodiment, the pneumatic weaving machine contains no relay-like arranged jets 5 and is fitted only with braking jets 9 and a picking jet or a system of main jets.
The control device for braking jets 9 can be made as a separate control device coupled with the control device of the weaving machine, or the activity of the braking jets 9 and of the relay-like arranged jets 5 can be controlled by a common control device coupled with the control device of the weaving machine, or the operation of the braking jets 9 and of the relay-like arranged jets 5 can be controlled directly by the control device of the weaving machine, etc.
The air used as a standard in all jets of pneumatic weaving machines can be replaced by another suitable medium.
One of possible embodiments of the pneumatic weaving machine with braking jets 9 is shown in Fig. 3. On the profile batten 1 of the weaving machine there is fixed the reed 2 with the direct pick channel 3 . One lateral side of the batten 1 carries a holder 20 of pick jets 21 whose outlet apertures are related to the entry of the direct pick channel 3 on the side of the reed 2 . The front side of the upper section of the batten 1 carries jet holders 18 situated apart at regular space intervals and receiving alternately relay-like arranged jets 5 and braking jets 9 The braking jets 9 are via electromagnetic valves 19 connected with an air chamber 190 suitably situated in the machine design and coupled with a pressure air source Z . The electromagnetic valves 19 are controlled by a control device 191 for weft 13 braking coupled with a not represented central control device. The control device 191 for weft 13 braking is adapted to be operatively coupled with a manual terminal 192 permitting to monitor and adjust the operation of the braking jets 9 .
The braking jet 9 is made as a hollow longitudinal body whose upper part is adapted to be inserted between (into) the warp thread system of the respective shed section. At its lower end, the braking jet 9 is fitted with a pressure air inlet aperture 90 . Near its upper end, it is fitted with an diffusion outlet aperture 92 oriented substantially transversely to the longitudinal axis 93 and serving to diffuse the pressure air stream getting out of the braking jet 9 . The diffusion outlet aperture 92 widens in the direction from the wall of the cavity 91 of the braking jet 9 , i.e., from the inner wall of the braking jet 9 to the outer wall of the braking jet 9 at least in the direction perpendicular to the longitudinal axis 93 of the braking jet 9 so that the pressure air stream leaving the diffusion outlet aperture 92 is being diffused against the reed 2 and acts on a major section of the length of the weft undergoing the picking unlike the embodiment with the relay-like arranged jets 5 supporting the weft 13 picking through the direct pick channel 3 where the pressure air stream is concentrated into the direct pick channel 3 . The diffusion outlet aperture 92 can take up various suitable shapes such as rectangular, oval, circular, etc.
At the lower end of the braking jet 9 , the cavity 91 has an initial cross section shaped with reference to the outer shape of the braking jet 9 . In the direction towards the upper end of the of the braking jet 9 with the diffusion outlet aperture 92 , the cavity makes a channel whose first section 940 follows the longitudinal axis 93 of the braking jet 9 and whose upper part is followed by a non-specifically curved bend consisting of a shaped part 94 terminating in the diffusion outlet aperture 92. In this way, the whole cavity 91 of the braking jet 9 makes a channel consisting of cross sections continuously following each other, diminishing in the direction of pressure air stream and arranged one after another in a non-specifically curved bend.
In the example of embodiment shown in Figs. 4a to 4e, the cavity 91 of the braking jet 9 is in the direction from its pressure air inlet aperture 90 to the diffusion outlet aperture 92 of the braking jet 9 made first as substantially cylindrical and situated in the direction of the longitudinal axis 93 of the braking jet 9 . The cylindrical section of the cavity 91 passes then into a flattened section which in its turn passes into a shaped section 94 marked by a continuously diminishing cross section and by gradual deviation from the longitudinal axis 93 of the braking jet 9 , and continuously followed by the diffusion outlet aperture 92 . In the shown example of embodiment, the shaped section 94 of the braking jet 9 is so continuously curved that the wall of the cavity 91 of the braking jet 9 on the side of the diffusion outlet aperture 92 first gets nearer to the longitudinal axis 93 , then gets farther from the longitudinal axis 93 of the braking jet 9 and passes into the upper side of the diffusion outlet aperture 92 . As is self-evident, the flattened middle and upper part of the braking jet 9 facilitates the insertion of the braking jet 9 between warp threads during the weaving.
The braking of the weft 13 being picked consists in bringing the weft 13 being picked and moving through the direct pick channel 3 at picking speed v in contact with a wall of the direct pick channel 3 , for instance with the bottom 4 of the direct pick channel 3 , thus producing friction between the moving weft 13 and the respective wall of the direct pick channel 3 , generating braking force T acting opposite the direction of the motion of the weft 3 and bringing the weft 13 to standstill. The absolute value of the weft 13 deformations is lower and the distribution of weft 13 deformations along the length of the weft 13 is uniform. The contact of the weft 13 with the respective wall of the direct pick channel 3 is brought about by pressure air streaming from the braking jets 9 either transversely to the direction of the weft 13 motion through the direct pick channel 3 in the direction against the respective wall of the direct pick channel 3 or in a direction at least partly opposite the direction of the motion of the weft 13 being picked through the direct pick channel 3 .
During its braking in the direct pick channel 3 , the weft 13 being picked can be acted upon either simultaneously along the whole of the length of the direct pick channel 3 , i.e.,by all braking jets 9 along the whole length of the direct pick channel 3 at the same time, or the action can be timed successively, by one braking jet 9 after another, from the beginning of the direct pick channel 3 to its end. During this successive action on the weft 13 being picked, the action on the weft 13 being picked can start at the initial section of the direct pick channel 3 even before the completion of the introduction of the picked weft 13 into the direct pick channel 3 .

Claims

A method of weft braking when picking the weft through a shed of a pneumatic weaving machine in which the weft (13) being picked through a direct pick channel (3) of the reed is exposed to a braking force acting opposite the direction of the weft motion, characterized in that the weft (13) being picked is in the direct pick channel (3) exposed to a force pressing it onto the wall of the direct pick channel (3) and thus braking the weft (3), reducing the absolute size of the weft (13) deformations and achieving their uniform distribution (13) along the weft (13) length.
A method as claimed in Claim 1, characterized in that the weft (13) being picked is acted upon simultaneously along the whole length of the direct picking channel (3).
A method as claimed in Claim 2, characterized in that the weft (13) being picked is acted upon along the length of the direct picking channel (3) successively from the beginning of the direct pick channel (3) to its end.
A method as claimed in Claim 3, characterized in that the force acting on the weft (13) being picked begins to work at the beginning of the direct pick channel (3) prior to the completion of the weft (13) insertion into the direct pick channel (3).
A method as claimed in any of Claims 1 to 4, characterized in that the weft (13) being picked through the direct pick channel (3) is exposed to the streams of a pressure medium oriented transversely to the direction of the weft (13) motion through the direct pick channel (3) against the wall of the direct pick channel (3).
A method as claimed in any of Claims 1 to 4, characterized in that the weft (13) being picked through the direct pick channel (3) is exposed to the streams of a pressure medium oriented into the direct pick channel (3) against its wall and at least partly opposite the motion direction of the weft (13) through the direct pick channel (3).
A braking jet (9) for a weaving machine made as a hollow body adapted at its upper end for entering between warp threads and fitted in the region of its upper end with at least one pressure air outlet aperture situated substantially transversely to the longitudinal axis of the braking jet, characterized in that the pressure air outlet aperture is made as a diffusion outlet aperture (92) arranged on the upper end of the cavity (91), the cavity being made as a channel consisting of cross sections continuously following each other, successively diminishing in the direction from the lower end of the braking jet (9) to its upper end and continuously arranged one after another in a non-specifically curved bend followed by the diffusion outlet aperture (92).
A braking jet as claimed in Claim 7, characterized in that the cavity (91) of the braking jet (9) is at its lower section cylindrical, turns to a flattened arrangement in the middle section of the braking jet (9), and from it on to a non-specifically curved bend.
A braking jet as claimed in any of Claims 7 or 8, characterized in that in the non-specifically curved bend of the cavity (91) the wall of the cavity (91) of the braking jet on the side near the diffusion outlet aperture (92) is bulged out in the direction of the longitudinal axis (93) and joins the lower side of the diffusion outlet aperture (92) while the wall of the cavity (91) of the braking jet (9) on the side remote from the diffusion outlet aperture (92) is continuously curved to a shape ensuring that it successively comes near to the longitudinal axis (93) of the braking jet (9), cuts the longitudinal axis (93) of the braking jet (9), and joins the upper side of the diffusion outlet aperture (92).