[0001] The present invention concerns a lever to operate the weft yarn gripping devices
in a pair of weft carrying and drawing grippers for shuttleless looms and, in particular,
the lever hingeing means.
[0002] As known, there is a persistent request on the textile market to constantly improve
the weft transport grippers of looms, and the devices mounted thereon, so that such
members may be apt to guarantee a perfect working even on the most modern looms in
very critical weaving conditions. In fact, for the production of high-quality precious
fabrics, the looms are required to provide increasingly higher weaving performances,
which particularly involve a high warp yarn tension, the use of very thin or delicate
weft yarns or of yarns with other special physical characteristics, and a reduced
shed angle; all this, combined with very high loom working speeds.
[0003] To obtain the aforementioned high weaving performances, it is thus indispensable
for a basic component of the loom, such as the pair of weft carrying/drawing grippers,
to undergo constant improvements in order to guarantee the required performances of
weft yarn insertion, together with a sufficiently long working life of the grippers.
Especially in planning the grippers, there has been a progressive reduction in size
of the single components, so as to produce grippers having a reduced mass and smaller
dimensions, and thus apt to stand more safely the alternate stresses imparted thereon
and to reduce the inertial loads on the loom.
[0004] To satisfy these requirements, the Applicant has conceived and set up an improved
structure for the pair of weft carrying/drawing grippers, thanks to which it is possible
to simultaneously obtain both an increase in the rigidity and wear resistance of the
grippers, and a reduction in the mass thereof. Said structure is the object of the
copending European Patent Application 99106429.6, the contents of which are incorporated
herein by way of reference.
[0005] In planning the aforecited pair of grippers, besides their general structural characteristics
it has also become considerably important to reduce in size the single devices mounted
thereon and, particularly, for what concerns the present invention, the weft yarn
gripping devices. Of course, the object of said reduction in size is to allow reducing
the overall dimensions of the grippers, with the double advantage of thereby reducing
both the mass of the grippers and the shed angle required to allow the grippers to
move between the warp yarns.
[0006] The inventor of the present invention has thus concentrated his attention on the
weft yarn gripping devices, particularly facing the problem to study a more compact
structure for the lever operating such devices. As known, in fact, the lever operating
the weft yarn gripping devices is normally fixed to the body of the gripper, in correspondence
of its hingeing point, by way of coaxial fixing means. The hingeing axis of said lever
thus has a fairly wide diametral width - seen that it must house the screw or rivet
for its anchorage to the gripper body - whereby, with such an enlarged diametral width,
it affects the final dimensions of the lever.
[0007] The object of the present invention is to thus supply an improved fixing system for
the lever operating the weft yarn gripping devices, in a pair of weft carrying and
drawing grippers for looms, said fixing system having a more compact structure, and
at the same time a higher mechanical resistance, to allow reducing the dimensions
of the gripper body meant to house the device, and simultaneously guarantee an increased
resistance of said device to the mechanical stresses imparted thereon.
[0008] According to the present invention, said object is reached with a lever to operate
the weft yarn gripping devices in a pair of weft carrying and drawing grippers for
shuttleless looms, of the type wherein the fulcrum of said lever is fixed to the gripper
body through suitable fixing means, characterized in that said fixing means are external
to the peripheral surface enveloping the lever.
[0009] In a first embodiment of the invention, said fulcrum consists of a cylindrical cavity
formed in the gripper body, into which engages, freely rotatable, a cylindrical portion
of the lever mating therewith, said cavity being formed between a cylindrical surface
integral with the gripper body and an opposed cylindrical surface of a counterthrust
block fixed to the gripper body through said fixing means.
[0010] In a second embodiment of the invention, said fulcrum consists of a pin onto which
is pivoted said lever, said pin being housed into a seat provided therefor in the
gripper body, an end of said pin being connected to said fixing means.
[0011] The invention will now be described in further detail with reference to some preferred
embodiments thereof, illustrated by way of example on the accompanying drawings, in
which:
Fig. 1 is an axonometric exploded view of a weft carrying gripper incorporating a
first embodiment of the lever to operate the weft yarn gripping device, according
to the present invention;
Fig. 2 is an axonometric view showing the operating lever - disassembled in the circle
II of fig. 1 - in a mounted position;
Fig. 3 is an enlarged scale view - similar to fig. 2 - showing the operating lever
with partly sectional and removed portions;
Fig. 4 is an axonometric view showing a detail of fig. 2, which represents - on an
enlarged scale and with partly sectional and removed portions - the seat for said
operating lever;
Fig. 5 is an axonometric exploded view of a weft drawing gripper incorporating a second
embodiment of the lever to operate the weft yarn gripping device, according to the
present invention;
Fig. 6 is an axonometric view showing the gripper, illustrated in fig. 5, in a mounted
position;
Fig. 7 is an axonometric view showing a detail of fig. 6, which represents - on an
enlarged scale and with partly sectional and removed portions - the pivoting bush
of the operating lever of fig. 5 or 6; and
Fig. 8 is an axonometric view showing a detail of fig. 6, which represents - on an
enlarged scale and with partly sectional and removed portions - the pivoting system
of the operating lever of fig. 5 or 6.
[0012] The first embodiment of the lever to operate the weft yarn gripping device, according
to the present invention, will now be described in detail with reference to figs.
1 to 4, which clearly illustrate the shape of the operating lever 1. The lever 1 comprises
- in addition to a front gripping portion 1a and to a rear operating portion 1p, of
a type known per se - a central cylindrical portion 1c, radiused in a V-shape to said
portions 1a and 1p. Said central cylindrical portion 1c of the lever 1 bears onto
a mating cylindrical surface 2 of a support base S of the lever 1, the revolution
axis of said cylindrical surface 2 coinciding with the desired rotation axis of the
lever 1. Said lever is produced from blanked steel, bent and forged, while the base
S is made from thermoplastic material - for example nylon, eventually with the addition
of teflon
® or other lubricating fillers - and fixed to the gripper body by screw means, as described
in the aforecited copending European Patent application.
[0013] The central portion 1c of the operating lever 1 is secured in position, against the
cylindrical surface 2 of the support base S, by a counterthrust block 4 (fig. 3).
Also said block is made from thermoplastic material and comprises a cylindrical portion
which perfectly mates with the corresponding cylindrical surface of the portion 1c
of the lever 1, having the same width of said surface. This structure is completed
by two vertical walls 3 of the support base S (fig. 4), projecting sideways from the
two external edges of the cylindrical surface 2 and delimiting on both sides the lever
1 to which they are perfectly adjacent. The walls 3 comprise two opposite holes, into
one of which is inserted a pin 6 (fig. 2) for fixing the counterthrust block 4. Said
pin 6 crosses entirely the block 4, in correspondence of the through hole 4f provided
therein, and is fastened - by snapping or screwing - into the opposite hole of the
wall 3. Said walls 3 finally comprise lateral nibs 3n at the top, between which is
restrained an upper projecting portion of the block 4, thereby preventing any possible
rotation of said block about the pin 6.
[0014] Thanks to this arrangement the lever 1 has only one degree of freedom, which means
- more exactly - that it is merely apt to rotate about the fulcrum formed by the cylindrical
bearing surface 2 of the support base S. In fact, the presence of the counterthrust
block 4 eliminates any possibility for the lever 1 to move in a vertical direction
and in a longitudinal horizontal direction, save for the required backlash, while
the walls 3 prevent any movements of the lever 1 in a transversal horizontal direction.
By suitably carrying out the injection molding process of the thermoplastic resin
portions, using materials with good characteristics of dimensional stability, it is
thus possible to obtain the required precision of alignment between the axis about
which rotates the lever 1 - namely, as already said, the revolution axis of the cylindrical
surface 2 of the support base S - and the weft yarn gripping surface, defined by a
lamina 5 fixed to said support base. In this respect, it should in fact be noted that
a perfect coplanarity between the gripping portion 1a of the lever 1 and the support
base S (or the lamina 5) guarantees the homogeneity of the pressing force during sliding
of the weft yarn between the gripping members, thereby preventing pressure peaks which
cause a number of defects in the fabric and/or deteriorate the quality of the yarn,
for example causing its "defibration".
[0015] The cylindrical surface 2 has a minimum angular development dimensioned so as to
stand, without getting deformed, the load imparted on the lever by the elastic reaction
of the springs M (visible in fig. 1) acting on the portion 1a of the lever 1, when
said lever opens through operation of its rear operating portion 1p. The maximum angular
development of said surface 2 should instead be dimensioned so as not to interfere
with the desired movement of the lever 1. An optimal angular development of the surface
2 is, for example, between 70° and 90°, and preferably about 80°. The cylindrical
surface of the counterthrust block 4 has an angular development corresponding to that
of the surface 2, or if desired, lower than that, due to the reduced loads which this
element has to stand during working of the lever 1.
[0016] If the cylindrical surface of the block 4 has an angular development equal to that
of the surface 2, the cylindrical portion 1c of the lever 1 should have an angular
development wider than that of the surface 2 by an angle at least equal to the maximum
rotation angle of the lever 1; only this arrangement allows in fact to guarantee a
correct rotation, with no interferences, of the cylindrical portion 1c inside the
annular cylindrical cavity formed between the surface 2 of the support base S and
the corresponding cylindrical surface of the counterthrust block 4.
[0017] As it appears evident from the previous description, the first embodiment of the
operating lever fully reaches the object of the present invention. Said lever may
in fact be reduced in size at will, exclusively in function of the weft yarn gripping
requirements, i.e. quite apart from the problems connected with the insertion into
the lever of its fixing means. Said means are in fact fully external to the peripheral
surface enveloping the lever and may thus be dimensioned independently from its size.
On the other hand, the lever 1 is guided in a very precise and reliable manner, seen
that it moves between cylindrical surfaces with a remarkable angular development;
this is highly advantageous also for the working life of the lever, since the wear
caused by the repeated angular movements of the lever affects a surface which is far
wider than that of the conventional pins. Finally, a possible take-up of the backlashes
can be obtained by simply replacing the block 4 - without hence involving the lever
1 - eventually increasing its size, so as to take into account any wear which might
have affected the surface 2 of the support base S.
[0018] Figs. 5 to 8 illustrate a second embodiment of the lever to operate the weft yarn
gripping devices, according to the present invention, applied to a weft drawing gripper.
Also in this case, the lever 10 is produced from blanked steel, bent and forged, but
its central portion 10c develops on a vertical plane, and not on a horizontal plane
as in the previous embodiment. The portion 10c is drilled in correspondence of the
rotation axis of the lever 10 and subjected to a local surface hardening treatment.
A bush 11 of integral hard metal - produced with an underwater cutting technique,
with no further grinding - is then inserted into the pivoting seat, thus formed, and
fixed into said seat by braze welding.
[0019] The lever 10 is then inserted into the gripper body, and precisely between the parallel
walls 12 forming its end portion, and is fixed to said walls - freely rotatable -
by means of the pin 13. Also said pin 13 is made from integral hard metal and is welded,
in correspondence of an end thereof, to the end of a connection plate 14 perpendicular
thereto. The other end of said plate 14 is drilled and connected to one of the walls
12 of the gripper body by means of a safety screw 15, parallel to the pin 13; said
screw 15 is thus suitably spaced from the pin 13, for example by a distance equal
to 8-10 mm.
[0020] Also the above arrangement hence allows to reach the object of the present invention,
namely to prevent the means fixing the fulcrum of the lever 10 from interfering with
the body of said lever and thereby affecting the dimensions thereof. In fact, according
to the invention, the fixing element consisting of the screw 15 is offset in respect
of the rotation axis of the lever 10, in correspondence of which there is only the
pin 13 of hard metal, having a small diameter, for example of 2 mm only. The seat
for the bush 11 must hence be sized merely in function of the small dimensions of
said pin 13 and can thus be far smaller than the seats for the operating levers adopted
up-to-date, which had to house also the fixing screw coaxial to the rotation pin of
said lever. This obviously allows to carry out at will a corresponding reduction in
size of the operating lever, without thereby interfering with the overall resistance
of said lever. Moreover, the reduced dimensions of the hole forming the seat for the
bush 11 produce less stresses into the body of the lever 10, thereby lengthening its
working life.
[0021] The present invention has been described with reference to two particular preferred
embodiments thereof, but it is evident that its protection scope is not limited to
said embodiments but extends to any possible variants, within reach of a technician
skilled in the art, falling within the definitions of the invention given in the following
claims.
1. Lever to operate the weft yarn gripping devices in a pair of weft carrying and drawing
grippers for shuttleless looms, of the type wherein the fulcrum of said lever (1;
10) is fixed to the gripper body by suitable fixing means, characterized in that said
fixing means (6; 15) are external to the peripheral surface enveloping the lever (1;
10).
2. Lever as in claim 1), wherein said fulcrum consists of a cylindrical cavity formed
in the gripper body, into which engages, freely rotatable, a cylindrical portion (1c)
of the lever (1) mating therewith, said cavity being formed between a cylindrical
surface (2) integral with the gripper body and an opposed cylindrical surface of a
counterthrust block (4) fixed to the gripper body through said fixing means (6).
3. Lever as in claim 2), wherein the revolution axis of said cylindrical surface (2)
of the gripper body coincides with the rotation axis of the lever (1).
4. Lever as in claim 3), wherein said axis is horizontal.
5. Lever as in claim 2), wherein said cylindrical surface (2) is formed into a support
base (S) for the gripping members, made from thermoplastic material and fixed to the
gripper body by screw means.
6. Lever as in claim 5), wherein said counterthrust block (4) is made from thermoplastic
material and is fixed, by means of a pin (6) which entirely crosses said block (4),
into a seat (3, 3n) formed in said support base (S).
7. Lever as in claim 6), wherein said seat for the counterthrust block (4) is formed
in one piece with said support base S and comprises two parallel vertical walls (3),
drilled along the axis of said pin (6) and provided with lateral nibs (3n) at the
top, apt to laterally restrain an upper projecting portion of said block (4).
8. Lever as in claim 7), wherein the distance between said walls (3) substantially corresponds
to the width of the central cylindrical portion (1c) of the lever (1) and to the width
of said counterthrust block (4).
9. Lever as in any one of the previous claims, wherein the angular development of said
cylindrical surface (2), integral with the gripper body, ranges between a minimum
such as to allow said surface (2) to stand, without getting deformed, the maximum
load imparted on the lever (1), and a maximum such as to prevent said surface (2)
from interfering with the rotary movement of said lever (1).
10. Lever as in claim 9), wherein said angular development is between 70° and 90°, and
preferably about 80°.
11. Lever as in claim 1), wherein said fulcrum consists of a pin (13), onto which is pivoted
the lever (10), said pin (13) being housed into a seat provided therefor in the gripper
body, an end of said pin (13) being connected to said fixing means (15).
12. Lever as in claim 11), wherein an end of said pin (13) is fixed to one end of a connection
plate (14) perpendicular thereto, the other end of said plate (14) being provided
with a hole into which are housed said fixing means consisting of a safety screw (15)
parallel to said pin (13) and engaged into the gripper body.
13. Lever as in claim 12), wherein the distance between said pin (13) and said safety
screw (15) is of about 8-10 mm.
14. Lever as in claim 11) of metallic material, wherein the pivoting seat for said pin
(13) is subjected to a surface hardening treatment.
15. Lever as in claim 14), wherein said pivoting seat houses a bush (11) of integral hard
metal, produced with an underwater cutting technique and fixed into said seat by braze
welding.