Conjugate cam shedding machine for looms

Abstract: In a conjugate cam shedding machine for looms - of the type having narrow-gauge conjugate cams which cause desmodromic oscillating movements of cam followers (13) controlling the heald frames - said cams form together a movable cam block (1), apt to part from said cam followers so as to allow their free oscillation. Said machine also comprises a mechanism (14), synchronized with the parting movement of the cam block and interacting with said cam followers in a plurality of different pre-selectable ways.

Description: The present invention concerns weave machines and, in particular, it relates to a conjugate cam shedding machine for looms, of the type allowing to obtain a positive or desmodromic movement of cam followers - consisting of levers with pairs of rollers conjugating with respective cams - which are apt to move the heald frames through a suitable linkage. The object of the invention is to introduce improvements in a machine of this type allowing, on one hand, to guarantee a more efficient working of the loom and, on the other hand, to improve the quality of the fabric being produced. For what concerns the configuration or arrangement of the cams and cam followers, there is already known to be a very advantageous solution according to which the cams and cam followers are set in a very compact arrangement - normally with a gauge of about 12 mm - equal to that of the heald frames, with the rollers of the cam followers positioned on two parallel planes, symmetrically offset in respect of a third middle plane parallel to the levers of the cam followers. It is also known to arrange for the two rollers of each cam follower to be fulcrumed on two pins, which are in turn fixedly connected to two shaped plate supports, and to choose - for the conjugating surfaces of the cams and of the cam followers - a recessed shape for the cams and a projecting shape for the cam follower rollers, or viceversa, so that said elements may reciprocally guide one another. All these arrangements of known technique allow to reach two fundamental objects: reducing as far as possible the gauge between cams and cam followers, and increasing as much as possible the dynamic performances thanks to the stout construction of said members. Further improvements have been brought to this machine by FR-A-2425490 disclosing the preamble of claim 1 and EP-A-512944 which assemble the cams in a cam block apt to part from the cam followers, so as to allow their free oscillation and, by EP-A-512944 which falls under Article 54(3) EPC, to use a mechanism syncronized with the parting movements of the cam block, taking a plurality of different preselectable positions of interaction with said cam followers. Nevertheless, even the most improved weave machines - as those having the aforementioned characteristics - are no longer apt to satisfy the increasing requirements of modern weaving. In fact, on account of the recent progress made in the weaving technique, said machines are required to perform functions which were not demanded in the past. In practice, a modern weave machine should be able to carry out: a) The automatic levelling of the heald frames with closed shed, during the loom stops due to breakage of the warp yarns or weft yarns. This function is extremely important to prevent faults in the fabric, which show up due to loosening of the warp yarns subjected to an increased tension in the open shed position. It is in fact known to the skilled in the art that, keeping the warp shed open for fairly long lengths of time - which is normal in looms upon stopping thereof - involves, due to over-tensioning of the yarns, a stretching which causes - as the loom starts working again, after the operator has intervened - an evident fault defined "bars". This fault can be eliminated if, during stopping of the loom and while waiting for the operator to intervene, the healds are levelled off in a closed shed position. b) The manual or automatic levelling of the heald frames with low shed. This function is important in sley reed cleaning operations, in that - by simultaneously lowering all the healds - it allows to part the warp yarns from the reed, thereby facilitating such operations. c) The high and alternatively low positioning of the heald frames, according to two lap sheds. This function allows to separate the warp yarns inserted into the even and, respectively, uneven frames. Said separation, called "sorting", is required for the operations of knotting the yarn tail ends of an empty beam with the yarn leading ends of a new beam. Considering that the operation of knotting and correctly joining the yarns is very delicate, also on account of the large quantities involved (thousands or tens of thousands of yarns), it is easy to understand how the sorting of the warp yarns is of primary importance in the loom feeding steps. The present invention allows to efficiently and suitably perform the above functions by means of a weave machine of the already mentioned type. The object of the invention is in fact a conjugate cam shedding machine for looms, of the type having narrow-gauge conjugate cams which cause desmodromic oscillating movements of cam followers controlling the heald frames, said cams forming together a movable cam block, apt to from said cam followers so as to allow their free oscillation, and comprising the features of the characterising part of claim 1. Preferably, in said machine, the cam block can be parted from the cam followers by rotation, about the oscillation axis of said cam followers, of a pair of eccentrics operating a pair of connecting rods, onto an end of which is fixed the cam block. The parting of the cam block from the cam followers allows the free oscillation of the latter. The rotation of said pair of eccentrics can be obtained by manual operation of a lever or, alternatively, by means of a motor-driven servomechanism. The pre-selectable synchronized mechanism comprises a partly cylindrical and partly comb-shaped crosspiece, the position of which can be varied both axially and angularly, so as to take up specific positions of interaction with the cam followers, according to said plurality of different ways. Said crosspiece preferably comprises a toothed sector engaging with a sprocket of the oscillation shaft of the cam followers, so as to synchronize with the parting movement of the cam block. Moreover, the axial and angular movements of said crosspiece, to pre-select said specific positions of interaction, are controlled by means of a prismatic pin operated by a handle with index, the specific positions of the crosspiece being determined by engagement of pin means thereof into fixed seats. Such a machine allows to pre-select the wanted position - out of said specific positions of interaction of the described crosspiece mechanism - by operating the handle controlling the prismatic pin, and to then part the cam block from the cam followers, thereby realizing the function corresponding to the pre-selected position. The invention is now described in further detail, with reference to the accompanying drawings, in which: Fig. 1 illustrates the arrangement with eccentrics, of the machine according to the invention, adopted to move the cam block close to and away from the cam followers, as well as the mechanism synchronized with the movements of the cam block, interacting with the cam followers; Fig. 2 is a general plan view of the arrangement and mechanism shown in fig. 1; Fig. 3 illustrates the synchronizing gear linkage, between the eccentrics and the pre-selectable mechanism, to perform the functions carried out with the weave machine according to the invention; Fig. 4 shows in further detail the pre-selectable synchronized mechanism of figs. 1 and 2; Fig. 5 illustrates the revolution trajectory of the crosspiece forming part of the mechanism of fig. 4 (pre-selected for the function of levelling the healds at the crossing) acting on the cam followers; Fig. 6 illustrates the trajectory of the same crosspiece, pre-selected for levelling the heald frames with low shed; and Fig. 7 illustrates the trajectory of the same crosspiece, pre-selected for lifting - in a first phase - the uneven heald frames, and - in a second phase - the even heald frames, so as to perform the function of sorting the warp yarns. As shown in figs. 1 and 2 of the drawings, the weave machine according to the invention comprises a cam block 1 (a single cam being shown in fig. 1) fixedly mounted on a drum 2 freely rotating, with the interposition of rolling bearings 3, about a shaft 4. The cam block 1 carries at its ends ring gears 5 engaging with sprockets 6 the rotation of which, controlled by a shaft 7, causes the rotary motion of the cam block 1. The rotation shaft 4 of the cam block 1 is in turn linked, through a U bolt 8, to two connecting rods 9, the small ends 9A of which are freely coupled with two eccentrics 10 which are in turn pivoted into the casing 11. The eccentrics 10 are both provided with a hole into which is mounted a shaft 12, which is in turn eccentric in respect of its end pins and which has the double function of connecting together for rotation the two eccentrics 10 and of acting as oscillation axis for cam followers 13 cooperating with the cam block 1. The eccentricity of the shaft 12 - in its central part - in respect of its end pins, is meant to guarantee a precise adjustment between the cam followers 13 and the respective cams 1, simply by a suitable rotation of said shaft 12. Finally, a manually operated lever 12A, provided with two fixed positioning stops, can be mounted on one side of the shaft 12. If wishing to operate automatically, the lever 12A can be replaced by a motor-driven mechanism causing the angular rotation of the shaft 12. The operation of the lever 12A (or that of the motor-driven mechanism replacing the same) causes the rotation of the pair of eccentrics 10, with the result of shifting the connecting rods 9 coupled therewith - and consequently the cam block 1 - in an upward direction. As the ring gears 5 roll over the respective sprockets 6, the cam block 1 moves away from the cam followers 13, which are thus free to oscillate on the shaft 12. The remaining figs. 3, 4, 5, 6 and 7, illustrate the pre-selectable mechanism synchronized with the rotation of the eccentrics 10, allowing the weave machine according to the invention to perform the functions for which it has been conceived. As shown in detail in fig. 4, said mechanism consists of a variably shaped crosspiece 14 comprising at least two significantly different portions: a portion 14A with a uniform cylindrical surface, and an angularly diversified comb-shaped portion 14B, comprising projections alternating with recesses having a gauge equal to that of the cam followers 13. During working, said surfaces - thus shaped - come into contact with the projecting part 15 of the cam followers 13, provided (fig. 3) with an antifriction sliding block 15A of plastic or other material. The crosspiece 14 is pivoted at its two ends, in a suitably eccentric way, on two clamp supports 16 and 17 (fig. 4), the first of which comprises a toothed sector 18 (fig. 3) engaging with a sprocket 19 keyed on the shaft 12 carrying the cam followers 13 and the eccentrics 10. A two-diameter pin 14C of the crosspiece 14 is normally inserted into one of four seats or cavities (16A, 16B, 16C, 16D) provided therefor in the support 16, thereby preventing the rotation of said crosspiece 14 about its eccentric axis. The portion of larger diameter of the pin 14C cooperates with the seats 16A, 16B, 16C, of corresponding diameter. Whereas, the portion of smaller diameter of the pin 14C cooperates with the seat 16D of corresponding diameter, which is very close to the seat 16C, thereby resulting axially displaced in respect of the three previous positions. The described gear drive guarantees the synchronism of the parting movement of the cam block 1 from the cam followers 13 by rotation of the shaped crosspiece 14. In fact the support 16, as well as housing the end pin 14C of the crosspiece 14, is locked with a tie clamp 20 onto a shaft 21 fulcrumed at its ends into the casing 11. In working, the rotation of the eccentrics 10 - produced by operating the shaft 12 - causes the rotation of the sprocket 19 keyed on said aft 12. The toothed sector 18 is thus also caused to rotate and, accordingly, the crosspiece 14 performs a revolutionary motion in respect of the shaft 21, thus acting on the projections 15 of the cam followers 13. As shown in figs. 3 and 4, the crosspiece 14 is provided at one end with a slot 22 apt to house the prismatic end 23 of a pin 24 controlled by a handle 25. The crosspiece 14 can thus be axially translated by operating the handle 25, in opposition to springs 26 and 27, hence allowing the outlet of the pin 14C from the seat of the support 16 into which it is engaged, and thus the rotation of said crosspiece always under control of the handle 25. With the help of a graduated scale 28 and of an index 29, provided on the handle 25, it is possible to angularly position the crosspiece 14 so as to align the pin 14C with the corresponding selected seat of the support 16. It will then be sufficient to release the handle 25 for the spring 27 to restore the correct axial position of the crosspiece 14, while the spring 26 will cause the handle 25 to return in the original idle position. The four seats 16A, 16B, 16C, 16D, of the support 16, each correspond to a different function of the crosspiece 14, and precisely, to the levelling of the healds with closed shed, to the levelling of the healds with low shed, and to the lifting of the even and, respectively, uneven healds for the sorting of the warp yarns. In other words, it is possible to pre-select the position of the crosspiece 14, among the four possible ones, in order to select the function having to be performed. The different operations of the above mechanism, allowing to perform each of the aforespecified functions, shall now be described. To level the healds in a crosswise position (fig. 5), it is necessary to pre-select the position of the crosspiece 14 - according to the already described modes - so that its cylindrical surface 14A may interact with the projection 15 of the cam followers 13. This is obtained by engaging the pin 14C into the seat 16A. By so doing, as one rotates the eccentrics 10 (either with the manual lever 12A or with the motor-driven servomechanism replacing said lever), in order to part the cam block 1 from the cam followers 13, the sprocket 19 - meshing with the toothed sector 18 - causes the rotation about the shaft 21 of the crosspiece 14 which, by gradually bearing onto the projection 15 of the cam followers 13, causes the rotation of these latter up to carrying the heald frames - connected to said cam followers through the linkage - in a levelled position with closed shed. The initial conditions are restored by reversing the rotation of the eccentrics 10. The levelling of the healds with low shed is obtained (fig. 6) by selecting the position of the crosspiece 14 more backward in respect of the projection 15 of the cam followers 13, with the pin 14C engaged into the seat 16B. In this position the crosspiece 14, while rotating about its axis, does not come in contact with the projection 15, whereby the cam followers 13, parted from the cam block 1, are free to rotate under the weight of the heald frames, thus resting onto a suitable stop 30; in these conditions, the frames are levelled on the low shed. As far as the lifting of the uneven and, respectively, even healds, the same is carried out in two similar phases (fig. 7). The angular position of the crosspiece 14 is selected so that its comb-shaped surface 14B may rest on the cam followers 13 and particularly against their projection 15. In a first phase, the pin 14C is inserted into the seat 16C with its portion of major diameter. With this arrangement, during rotation of the crosspiece 14 - synchronized with the parting of the cam block 1 from the cam followers 13 - only the projecting parts of the comb 14B can act on the cam followers 13, while its recessed parts remain inactive. Seen the alternance of projecting and recessed parts in the comb 14B, only the heald frames of the operated levers will thus be lifted, while the others will remain in a low position. In a second phase, after the initial conditions have been restored, the position of the crosspiece 14 will be selected - always with its projecting comb parts 14B facing the cam followers 13 - only after having axially shifted said crosspiece 14 by one step, corresponding to the gauge of the cam followers 13. This is obtained by inserting the portion of minor diameter of the pin 14C into the seat 16D, which is very close to the seat 16C, the angular position of the crosspiece 14 thus varying to a very slight extent, while its axial position is considerably modified. In this manner, by repeating the rotation of the crosspiece 14, the previously inactive cam followers 13 shall be operated, while the previously operated cam followers 13 will symmetrically remain inactive. This operation will allow to obtain the two alternate lap sheds, by lifting in a first phase the uneven heald frames and in a second phase the even heald frames.

Claims: Conjugate cam shedding machine for looms, of the type having narrow-gauge conjugate cams which cause desmodromic oscillating movements of cam followers (13) controlling the heald frames, said cams forming together a movable cam block (1), apt to be moved away from said cam followers (13) so as to allow their free oscillation, characterised in that it comprises a mechanism (14) synchronized with the parting movement of the cam block (1) and having a plurality of different preselectable positions of interaction with said cam followers (13), and in that four specific positions of interaction between said mechanism and said cam followers (13) are provided, in correspondence of which one obtains the levelling of the heald frames with respectively closed shed (Fig. 5), low shed (Fig. 6), and two lap sheds for the sorting of the warp yarns (Fig. 7). Conjugate cam shedding machine as in claim 1), wherein said cam block (1) can be parted from the cam followers (13) by rotation, about the oscillation axis of said cam followers (13), of a pair of eccentrics (10) operating a pair of connecting rods (9), onto an end of which is fixed the cam block (1). Conjugate cam shedding machine as in claim 2), wherein the rotation of said pair of eccentrics (10) is obtained by manual operation of a lever (12A). Conjugate cam shedding machine as in claim 2), wherein the rotation of said pair of eccentrics (10) is obtained by means of a motor-driven servomechanism. Conjugate cam shedding machine as in any of claims 1) to 4), wherein said synchronized mechanism comprises a partly cylindrical (14A) and partly comb-shaped (14B) crosspiece (14), the position of which can be varied both axially and angularly, so as to take up each one of the four specific positions of interaction with the cam followers (13). Conjugate cam shedding machine as in claim 5), wherein said crosspiece (14) comprises a toothed sector (18), engaging with a sprocket (19) of the oscillation shaft (12) of the cam followers (13) so as to synchronize with the parting movement of the cam block (1). Conjugate cam shedding machine as in claim 6), wherein the axial and angular movements of said crosspiece (14), to pre-select said specific positions of interaction, are controlled by means of a prismatic pin (24) operated by a handle (25) with index (29). Conjugate cam shedding machine as in claim 7), wherein said four specific positions of the crosspiece (14) are determined by engagement of pin means (14C) of said cross piece (14) into fixed seats (16A-16D)

Inventors: BURIGANA LUCIO, SERTURINI GIUSEPPE, BURIGANA, LUCIO, SERTURINI, GIUSEPPE
Applicants: FIMTESSILE, FIMTESSILE FABBRICA ITALIANA MACCHINARIO TESSILE S.P.A.
Application year: 1992
Main classification: D03C5
IPC codes: D03C5, D03C13