GB2034766A - Shed Forming Device for Looms - Google Patents

Abstract

Intermittent motion is given to a shedding mechanism by providing a continuously rotating shaft 2 with cams 5, 6 which act on axially staggered groups of followers 7 to 14 after the manner of a Geneva mechanism. <IMAGE>

Description

SPECIFICATION Shed Forming Device for Looms This invention relates to a device for shed formation in looms, that is to say a device which by acting upon the heald frames will establish the law by which the warp yarns are moved and accordingly produce the pattern of the fabric being worked out.

Several devices are already known which provide shed formation, such as the so-called dobbies, cam weave machines and Jacquard machine.

It is also known that the application of these machines to looms of the type wherein weft transfer members which are positively moved within the shed (such as weft holder pliers and the like) and not launched therethrough (such as shuttles and projectiles) involve various disadvantages for each type of device, thus providing a need for more satisfactory solutions than those hitherto proposed.

The present invention provides the application in such devices or in some of such devices of an interrupting member for introducing pulses to the movement of the heald frames during a whole revolution of the loom shaft.

In fact, for example, it can be seen that while in the cam weave machines the iaw for moving the heald frame is already determined, as desired by the suitably designed profile of the cam, in Jacquard machines should a cam not be provided for the dog movement, but as usual a movement generated by a connecting rod-crank assembly is used, an uninterrupted movement is obtained, which is clearly detrimental in that the continuously moving warp yarns would tend to modify in a surely undesired manner the direction of the weft holder pliers. This involves faulty weft exchanges at the center of the shed, unreliability in operation, and early wear of the parts or members directly contacting the warp yarns.

Therefore, it was thought that the application of an interrupting member, not necessarily essential in a cam weave machine, would provide in a Jacquard machine, still during the rotation of one revolution, a complete movement for the dogs, which would no longer take place in a whole revolution of the primary shaft of the loom, but for example much more rapidly within an arc of 1800--3600, thus permitting pause periods in such a movement.

On the other hand, said interrupting member appears to be of no interest in the case of conventional type of dobbies reciprocated by rocking lever and knives, since the drive for the inner members is provided by side cams by suitable laws.

Finally, in the rotating type of dobbies, wherein the raising and lowering movement of the heald frames is provided by linkages driven by cams or eccentrics, which the clutches controlled by the pattern paper of the fabric to be made would render sometimes integral with the continuously rotating drive shaft and sometimes released therefrom to take the fixed position, the application of an interrupting member becomes essential to provide the required pauses in the eccentric or cam motion, during the continuous motion of the drive shaft, for mechanically correctly activating and disactivating said clutches.On the other hand, in the same type of rotating dobbies, the use of an interrupting member provides in addition to the required pauses for activation and disactivation of said clutches, corrections to the eccentric movement laws (specifically by reducing the undesired acceleration peaks which would otherwise be imposed to the movements of the healds frames), thus obtaining the same advantages as above indicated for Jacquard machines.

At last, the application of a device for interrupting the rotational movement of the drive shaft in weave machines may therefore find wide spread and interesting applications, which will then be developed and specified by designers and users.

A device for shed formation according to the present invention is substantially characterised in that its drive shaft is intermittently rotatably moved by means of a cam interrupting member interposed between said shaft and an inlet shaft connected with the general movement of the loom to which the device is applied. This interrupting member comprises a driving element formed of a double profile cam keyed on said continuously rotating inlet shaft, and a driven element comprising two side-by-side pluralities of feeling rollrs idly mounted at equal angular spacings on the flanged periphery of a sleeve or bush keyed to said intermittently rotating drive shaft, each of the profiles of said cam being constantly in engagement with at least one of the corresponding plurality of feeling rollers.

The invention will now be further described by way of example with reference to the accompanying drawings in which: Fig. 1 is a front view of an interrupting member embodying the invention; Fig. 2 is an axial sectional view of the same member as in Fig. 1; and Figs. 3 to 1 5 sequentially show the significant operating positions of the interrupting member shown in Figs. 1 and 2.

A device for shed formation according to the invention has its member driven by an interrupting member and comprises a driving element 1 keyed to the inlet shaft 2 which is uniformly continuously rotatably driven by the movement of the loom to which the shed forming device is applied, and a driven element 3 keyed to an outlet shaft 4 forming the drive (intermittently moving) shaft of the device.

As shown in the drawings, the driving element 1 comprises a cam having two profiles 5 and 6, both of which have a circular arc section (that is of constant radius) and another section of varying curvature and radius. In turn, the driven element 3 has two side-by-side pluralities of feeling rollers 7, 9, 11, 1 3 and 8, 10, 12, 14, respectively, idly mounted and equally spaced on the periphery of flanges 15, 16 and 17 of a sieeve or bush 18 keyed to the outlet shaft 4. More particularly, the rollers 7, 9, 11 and 13 are uniformly arranged and alternated with rollers 8, 10, 12 and 14.

The two elements 1 and 3 are mutually arranged, so that the profile 5 of the former constantly engages at least one of said rollers 7, 9, 11 or 13, whereas the profile 6 constantly engages at least one of said rollers 8, 10, 12 or 14. It will be readily understood that the rotation of cam 1 causes the roller sleeve 3 to rotate when the feeling rollers of the latter are engaged by the varying curvature and radius portions of the cam profiles, while the motion of element 3 and accordingly of shaft 4 will be subjected to pauses when the feeling rollers are engaged by the constant curvature and radius sections of the profiles 5 and 6 of cam 1.

In Fig. 1, the device embodying the invention is shown at the stall position of shaft 4. In fact, upon a slight rotation of shaft 2 in clockwise direction shown by arrow F, it does not correspond any rotation of shaft 4, since both roller 7 engaged with profile 5 and roller 8 engaged with profile 6 both contact the constant radius sections of said profiles. On the other hand, fancing to continue the rotation of shaft 1 in the direction of arrow F, the roller 7 will at some time contact the point or tip H of profile 5, and roller 8 will contact the point or tip K of profile 6, that is varying radius sections of said profiles. From now on the profile 5 of cam 1 will cause roller 7 to move and accordingly sleeve or bush 1 8 and shaft 4 to rotate, while roller 8 will merely roll over a section of profile 6 developed by the movement of said roller 8.Thus, the rotation will occur without any clearance and the highest accuracy.

Should rotation of shaft 2 be continued, then at some time said profile 6 engages one of the rollers of element 3, while another roller merely rolls on profile 5. Other stall periods could also be provided by further constant radius sections (herein not shown) of said profiles, and so on.

We deem it unnecessary to further describe the cooperation between the profiles 5 and 6 of cam 1 and rollers 7-14, neither the sequential development of the movements for the driven element 3 and shaft 4 as shaft 1 rotates; however, by way of example, such movements are shown in detail in a sequence-starting at Fig.

1-in Figs. 3 to 15 of the accompanying drawings, which as per the foregoing do not require any explanation. It should only be noted that the position of Fig. 1 5 is again a stall position for shaft 4 and that to a complete revolution of shaft 2 will correspond just half a revolution of shaft 4 plus the desired stall or pause corresponding to the single constant radius section of the profiles 5 and 6 of the drawn cam 1. Therefore, the type of intermitting member shown and described is a two-station intermitting member, since to two revolutions of inlet shaft 2 it corresponds one revolution in two clearly distinct steps of outlet shaft 4.However, it is evident that the foregoing description and drawings are given by mere way of example and that, accordingly, the number of stations with the associated movement and pause angles of the device could be changed, as above mentioned.

It should be noted that in an intermitting member according to the invention said stall or pause angle may range between 0 and 1 80C, being limited in the embodiment shown to about 90".

It will be appreciated that the mechanical solution adopted for the intermitting member substantially differs from the conventional conjugate cams and rocking lever mechanism; as a matter of fact profile 5 is not the primary profile, neither profile 6 is the conjugate profile, but the thrust or drive section always lies on one side (on the right in the representation of Fig. 1) in respect to the center of rotation for the feeling roller, whereas the profile section on the other side (on the left) is the conjugate profile.

The cam and feeling roller assembly according to the invention can be compared with the involute toothing profiles of a pair of gears. As a matter of fact it could be stated that profiles 5 and 6 of cam 1 operate on an imaginary gear comprising eight rollers.

It is understood that the design of profiles 5 and 6 of cam 1, the number of rollers mounted on said sleeve or bush 1 8 and further constructive details of the intermitting member used in the shed forming device shown and described may widely vary without departing from the scope of the present invention.

Claims (6)

Claims

1. A device for carrying out shed formation in looms wherein the drive shaft is intermittently rotatably driven by means of a cam interrupting member interposed between said shaft and an inlet shaft connected to the general movement of the loom to which said device is applied.

2. A device according to claim 1, wherein said interrupting member comprises a driving element formed of a double profile cam keyed to said continuously rotating inlet shaft, and a driven element comprising two side-by-side pluralities, or sets, of feeling rollers idly mounted at equal angular spacings on the flanged periphery of a sleeve, or bush, keyed to said intermittently rotating drive shaft, each of the profiles of said cam being constantly engaged with at least one roller of the corresponding plurality of feeling rollers.

3. A device according to claims 1 or 2, wherein said cam has corresponding constant curvature and radius sections of said profiles.

4. A device according to claim 3, wherein the constant curvature and radius sections of said profiles extend through an arc in the range of 0 to 1800.

5. A device as claimed in claim 4, wherein said constant curvature and radius sections of said profiles extend through about 900.

6. A device for carrying out shed formation in looms substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.