EP0566506B1 - Device for reciprocating the knives in heavy centre-shed dobbies - Google Patents

Description

The present invention relates to heavy dobbies used for training the crowd on very large weaving machines, of the kind in particular of those used for the manufacture of tubular fabrics suitable for the production of felts or dry endless filters for pulp industry.

Due to the very large amplitude of the heald frame travel associated with these dobbies, conventional open crowd systems cannot be used and dobbies with closed steps must be used, that is to say in which each frame moves down or up from a middle position corresponding to the cross point of all the frames.

In fig. 1 of the drawing appended hereto, we have very schematically recalled the general arrangement of heavy dobbies with closed pitch of the conventional type. Each of the heald frames CL mounted on the weaving machine is connected by a connecting rod 1 to a corresponding oscillating lever 2, articulated at 2 a on the fixed frame; opposite this point 2 a , each lever 2, provided with a stop 2 b , supports a double tilting hook 3 which is pivotally controlled by pushers of the dobby reading mechanism in order to selectively engage with either of two actuating knives 4, which, suitably guided horizontally, are controlled to move alternately in unison in opposite directions.

The actuation of all of the double hooks 3 by the reading mechanism takes place when the two knives 4 are in the central position (levers 2 oriented vertically) and it is understood that depending on whether a hook comes to cooperate with the 'either of the knives 4, the corresponding CL frame moves vertically up or down from the position corresponding to the closing of the pitch.

The mechanism for the alternating control of the two knives 4 comprises, at each of the opposite ends thereof, a link 5 articulated on the one hand to one of said knives, on the other hand to a beam 6 capable of oscillating around d a support axis 7. Each of the two flails 6 is equipped with two rollers 6 a and 6 b which roll on the tracks 8 a and 8 b of an additional cam 8 wedged on a shaft 8 c , driven in continuous rotation, through a transmission shown schematically in 9, by the engine of the machine matching weave.

We understand that if such a mechanism allows to give the two knives 4 the desired alternative movement, its operation at the high speeds now imposed on the weaving machines becomes very random, due in particular to the length of the kinematic chain, which includes a number important joints likely to take play. Weaving defects are therefore relatively frequent.

It is to this drawback that the present invention intends to remedy, which relates to the heavy dobby with closed pitch which is defined in claim 1.

In fact, the invention essentially consists in providing on each side of the actuating knives two drums rotating in synchronism, which are oriented parallel to the direction of alternating movement of said knives and whose periphery is hollowed out by two grooves with corrugated profiles. reversed which cooperate with the ends of each of the knives, so that the rotation of these drums ensures desmodromically the alternating movement of said knives in opposite directions.

The appended drawing, given by way of example, will allow a better understanding of the invention, the characteristics which it presents and the advantages which it is capable of providing:

As indicated above, fig. 1 schematically illustrates the general arrangement of a dobby with closed pitch of the conventional type.

Fig. 2 is a perspective view illustrating the arrangement of a dobby established in accordance with the present invention.

Fig. 3 is a detail section illustrating the cooperation of the drums and the ends of the knives.

In fig. 2, the reference 11 designates the two reciprocating knives which, in the conventional way, are intended to cooperate selectively with the double tilting hook 13 pivotally mounted at the upper end of each of the oscillating levers 14 connected by a connecting rod assembly 15 to the corresponding heald frame. It is on these hooks 13 that the pushers (not shown) of the usual dobby reading mechanism act, in the manner which has been described above.

To provide alternative control of the two knives 11, the invention uses two drums 16 carried by shafts 17 oriented transversely to the axis of said knives, that is to say parallel to the direction of movement to be imparted to these last. The two shafts 17 are connected to each other by a toothed belt 18 associated with two corresponding pulleys 19 and one of these shafts extends axially at 17 'to be kinematically linked to the shaft (not shown) of the weaving machine controlled by the envisaged dobby, or that of an independent motor.

Each drum 16 is hollowed out by two grooves 16 a inside each of which is engaged a roller 12 (fig. 3) mounted idly on a stud 11 a , provided axially at each of the ends of the knives 11. It is easily understood that by means of an appropriate corrugated profile of the grooves 16 a and a suitable offset of the latter, the rotation of the drums 16 will impart to the knives 11, introduced between horizontal guides shown diagrammatically at 20, the desired alternative movement.

The inversion of the movement of each knife takes place gradually, without sudden jerk. Furthermore and above all, the knives 11 are directly connected to the profile of the grooves 16 has drums 16, without any intermediate articulation; the movement is thus likely to be of perfect quality, absolutely unchanging in time. The dobby according to the invention can thus operate at very high working speeds, without parasitic vibrations and without risks of weaving defect. It will also be observed that its structure is more compact and more economical than traditional structures.

It goes without saying that the transmission 18-19 by belt and toothed pulleys can be replaced by any other system (chain, gears, etc.) capable of ensuring a strictly synchronous drive of the two drums 16.

Claims (2)

1. A heavy closed-shed dobby, of the type comprising two actuating blades (11) driven in an opposed alternating movement to cooperate selectively with a rocking double hook (13) borne by each of the pivoting levers (14) connected to the heald frames (CL) of the corresponding weaving machine, characterised in that it comprieses two drums (16) rotating synchronously, which are oriented substantially parallel to the trajectory of the blades (11) and the periphery of which bearas two grooves (16a) with undulating inverse profiles, within which there are engaged pins (11a) provided axially at the end of each blade.
2. A dobby according to Claim 1, characterised in that the two drums (16) are driven synchronously by means of a transmission by a belt and notched pulleys (18-19), by a chain or by gears.

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