EP0462035B1 - Centre-shed dobby for looms - Google Patents

Description

The present invention relates to dobbies for the control of heald frames which train the crowd on the weaving looms.

We know that the vast majority of textile dobbies, whether of the rotary type or with oscillating scales, are arranged to work in an open crowd, in the sense that during each cycle, they actuate the heald frames so that that they complete a total vertical stroke, without stopping at the middle position corresponding to the closing of the step. However, in certain cases and especially for weaving very wide tubular fabrics, heavy dobbies operating in a closed crowd must be used, the heald frames then being controlled to move from the central closed position in the direction of either of the extreme open positions.

The heavy dobbies with closed crowd currently on the market generally have the structure very schematically illustrated in FIG. 1 of the accompanying drawing. For each heald frame a , the mechanism comprises an arm b which is coupled to said frame by a pulling system c associated with a linkage or other connecting device; opposite its pivot point d , each arm b is equipped with a double hook e of the tilting type, controlled at one or the other of its ends by the reading device f containing the weaving program. To the set of arms b are associated two independent knives g which are actuated to move simultaneously with the spacing and the approximation, on either side of a median position for which they are applied against the free end of each arm b .

It is understood under these conditions that depending on whether the reading device f controls the double hook e to secure the arm b with one or the other of the two knives g , the heald frame a will move vertically either upwards, either down, from the middle position for which the crowd is closed. The stroke of each frame a can thus, when desired, be reduced by half compared to the case of conventional dobbies with an open crowd.

It should nevertheless be observed that the structure of the known heavy dobbies, as recalled above, has disadvantages not negligible in practice. It is understood in particular that the knives g must mark a stopping time when they arrive in the middle position, so that the device f can tilt the hook e in one direction or the other; However, this downtime obviously results in a significant reduction in the speed of operation of the dobby and the loom, at the same time as it involves harmful acceleration and deceleration effects.

It has also been proposed, in particular in French patent No. 2,005,766 STAUBLI, dobbies capable of working in an open crowd, in a closed crowd or in a mixed crowd, in which the traction levers controlled by the actuating elements placed under the dependence on the weaving program are connected to the draw system of each heald frame by means of a pivoting arm which is associated with additional actuation means capable of imparting to said arm a periodic oscillating movement in synchronism with the cycle of control of the aforementioned actuating elements.

In the aforementioned French patent, the intermediate pivoting arm is pivotally mounted on a fixed axis while the additional actuation means are constituted by a cam mechanism. Against the periphery of this cam is elastically applied a follower roller carried by the pivoting arm considered, which is connected to the corresponding traction lever by a sliding system.

The operation obtained using such a structure is not entirely satisfactory and the user faces significant drawbacks in practice. It can in particular be noted that the control of the swing arm is not ensured in a positive manner; the cam mechanism can only give a lifting movement to the corresponding heald frame.

In other types of dobby capable of working in an open crowd as well as in a closed crowd, the actuating elements are brought together in pairs so that in each pair, one of said elements ensures normal control of the traction lever of the pair considered while the other is capable of giving the pivoting arm coupled to said lever an additional cyclic movement corresponding to the closed crowd. We can refer to this point to the French Patents 2,486,111 (STAUBLI) and 2,106,164 (STAUBLI).

Such a system does indeed make it possible to obtain a positive control, but the obligation to couple the actuating elements two by two obviously reduces by half the number of heald frames capable of being controlled by the dobby for the same size of this one.

It is all of the drawbacks of the various types mentioned above that the present invention intends to remedy, which relates to the dobby for weaving loom which is defined in claim 1.

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 is a diagram illustrating the arrangement of certain conventional heavy dobbies with a closed crowd.

Fig. 2 is a perspective view showing the arrangement of a dobby according to the invention.

Fig. 3 and 4 are cross sections of the oscillating chassis of the dobby according to fig. 2, the parts being shown in the two working positions of the corresponding actuating element.

Fig. 5 and 6 schematically illustrate the general operation of the dobby.

Fig. 7 finally shows two diagrams which show the movement imparted to one of the heald frames, by a dobby according to the invention in the upper part, by a conventional dobby of the type according to FIG. 1 in the lower part.

The dobby according to the invention comprises a set of actuating elements 1 (fig. 2) quite similar to those of a conventional dobby of the rotary type. It did not detail the arrangement of these elements 1 and it will be sufficient to remember that each of them is constituted by a cam 1 mounted on a shaft 2 common to all said elements 1, the angular connection of the eccentric 1 a with shaft 2 being provided by a coupling member (not shown) placed under the dependence of the dobby program reading device. The eccentric 1a is housed in an eccentric opening of a connecting rod 1b of which the free end is coupled in 3a with a pull lever 3.

All the traction levers 3 of the dobby pivot on a common axis 4 oriented parallel to the shaft 2 and it is understood that when the eccentric 1 a is angularly connected with said shaft, the rotation of the latter over 180 ° imparted to the element 1 envisaged and to its traction lever 3 an oscillating movement. In the known rotary dobbies is on the terminal spout 3b of the levers 3 that is fixed flue system associated with the frame envisaged smooth.

By cons, in the case of the dobby according to the invention, on each traction lever 3 is freely articulated in 3 c a double arm 5 with a square profile which is equipped with a roller 6 at one of its ends , while the opposite end forms a mooring point for a collar 7 provided at the end of the pulling system 8 of one of the heald frames 9 of the loom. The roller 6 is engaged with reduced clearance in a slot 10 a made inside the profile of a movable part 10 forming a cam, so that the arm 5 is ultimately freely coupled, by three movable joints, at lever 3, to the draft system 8 and to the cam 10.

All the parts or cams 10 are engaged and clamped axially on two rods 11 oriented parallel to the shaft 2 and carried by lateral flanges 12. Each of the latter is integral with a lateral pivot 13 rotatably supported by the frame (not shown) of the dobby, so that the assembly 11-12 constitutes a sort of chassis capable of oscillating along the axis of the pivots 13, it being observed that this axis 13-13 passes through the center of symmetry of the light 10 a of each cam 10, which light defines the path of the roller 6 which it controls.

One of the flanges 12 is joined by a link 14 to an end of an axle 15 secured to a toothed wheel 16 which meshes with a wheel 17 with a larger diameter wedged on the shaft 2. It is understood that the assembly 14 -15 forms an eccentric crankpin which, during the jerky rotation of the shaft 2, imparts to the chassis 11-12 and to the cams 10 mounted thereon an oscillating movement centered on the pivot axis defined by the pivots 13. We note that the diameter of the toothed wheel 17 is equal to twice that of the toothed wheel 16, so that the frame 11-12 is driven by two oscillations at each revolution of the shaft 2, the latter being, as usual in rotary dobbies, animated by an intermittent angular displacement with stop every 180 °.

Obviously and in the manner illustrated in FIG. 3, as a result of the engagement of the roller 6 in the lumen 10 a of each cam 10, the periodic oscillation of the frame 11-12 is transmitted to the arm 5 and to the pulling system 8 associated with the said cam, which has for effect of operating the displacement of the frame 9. It is essential here to observe that the particular profile of the light 10 a allows the arm 5 to oscillate in either of the two operating positions of the lever. traction 3 considered, the roller 6 to slide freely in said opening 10 a when the lever 3 changes its direction under the effect of the actuating element 1, as clearly shows the comparative examination of fig. 3 and 4.

This systematic operation is also shown in the diagrams according to fig. 5 and 6, in which the length of the two parts of the double arm 5 has been increased to better illustrate the invention. It can be seen in particular that the amplitude d of the oscillating movement of the collar or fastener 7 remains identical regardless of the orientation that the connecting rod 1 b of the actuating element gives to the traction lever 3, this movement being simply arranged in one or the other of two symmetrical zones according to the weaving program.

We therefore obtain well for the heald frame 9 the closed crowd stroke indicated on the diagram which appears in the upper part of FIG. 7: as long as the actuating element 1 placed under the dependence of the weaving program has not modified the orientation of the traction lever 3, this frame 9 moves alternately from the middle position corresponding to the closing of the pitch , upwards or downwards for opening and passage of the pick, and vice versa. We will observe in fig. 5 or 6 that the amplitude of the vertical movement of the frame 9 is liable to be modified (value d ′ following dotted line) by adjusting the longitudinal position of the collar 7 along the upper part of the double arm 5, being at surplus noted that this adjustment can be differentiated according to the arms of the dobby.

This independence of the settings is also reflected in the ability to obtain a mixed or mixed crowd, the pulling system 8 being able, depending on the frames 9, to be attached either to the arm 5 or to the terminal spout 3 b lever 3.

It is interesting to note that, unlike the classic system shown diagrammatically in FIG. 1, the dobby according to the invention works without play. The movement of the frames 9 in operation in a closed crowd is carried out in a harmonious manner, without stopping in the middle closed position (the comparison with the lower diagram in FIG. 7 makes it clear the situation), which in fact eliminates harmful stresses and the phenomena of acceleration and braking mentioned at the beginning of this document. The dobby is thus capable of working at significantly higher operating speeds than the usual heavy dobbies.

The invention is capable of being implemented with actuating elements produced as well according to the rotary system mentioned above and described as according to the HATTERSLEY system (hook scales). On another level, one could imagine for the oscillating control of the intermediate arm 5 cam mechanisms different from that (roller 6 / light 10 a ) which has been illustrated herein, these cam mechanisms being able themselves to be replaced by any other suitable means of actuation.

Claims (7)

1. Dobby for weaving loom, of the type in which at least certain of the traction levers (3) controlled by the actuation elements (1) placed under the dependence of the weaving program incorporated in the reading device are connected to the drawing system (8) of the corresponding heddle frame (9) via a pivoting arm (5) which is associated with additional actuation means (10) adapted to impart thereto a periodic oscillating movement in synchronism with the control cycle of said actuation elements (1), characterized in that the pivoting arm (5) is freely supported by three mobile points of coupling which connect it respectively to the traction lever (3) in question, to the corresponding drawing system (8) and to the actuation means (10), whilst these latter are arranged to ensure a permanent positive control of said arm in order to tend systematically to return the corresponding heddle frame (1) in the sense of closure of the shed, whatever the position of this frame.
2. Dobby according to Claim 1, characterized in that, at its end opposite the one which is coupled to the drawing system (8), the pivoting arm (5), presenting a profile in angle form, is equipped with a roller (6) introduced in a slot (10a) made in a cam (10) which, in order to constitute the additional actuation means, is borne by a pivoting chassis (11-12) animated by an oscillating movement.
3. Dobby according to Claim 2, characterized in that the pivot axis (13-13) of the oscillating chassis (11-12) merges substantially with the axis of symmetry of the slot (10a) which defines the path of the roller (6).
4. Dobby according to either one of Claims 2 and 3, characterized in that the oscillating chassis is constituted by two lateral elements (12) joined by two parallel rods (11) along which the assembly of cams (10) is tightened.
5. Dobby according to any one of Claims 2 to 5, characterized in that the oscillating movement is imparted to the chassis (11-12) by a crank pin (14-15) driven by the principal shaft (2), the speed of revolution of the crank pin being double that of said shaft.
6. Dobby according to Claim 5, characterized in that the crank pin (14-15) is borne by a toothed wheel (16) which meshes with a toothed wheel (17) fitted on the principal shaft (2), the ratio between the wheels (16, 17) being 1/2.
7. Dobby according to any one of Claims 1 to 6, characterized in that each drawing system (8) may be equally well coupled to one of the arms (5) or to a terminal beak (3b) of one of the traction levers (3).

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