[0001] The present invention relates to a carrying or drawing gripper for a weaving loom,
specifically a gripper with a flexible gripping system.
[0002] It is known that in gripper weaving looms a pair of grippers is used, one being a
drawing gripper and the other being a carrying gripper, in order to carry the weft
yarn through the shed.
[0003] Weaving grippers have various design and operating modes. One of these, which will
be referred to in the following description, is so designed that grasping of the weft
yarn is performed by a flexible metal strip which is suitably pushed against an abutting
surface of a plate integral with the gripper body.
[0004] An example of such a gripper is depicted in fig. 1, which represents an elevation
side view of a prior art gripper marketed under the brand SOMET and the identification
code BDL311F.
[0005] The gripper comprises a main body 1, intended to be secured to a gripper-mounting
strap (not shown), onto which a flexible gripping metal strip 3 is mounted through
the fastening means 2, capable of engaging with a plate 4, integral with the gripper
body 1.
[0006] Between the front end of the flexible metal strip 3 and the fixed plate 4, the weft
yarn is intended to be grasped (not shown). In order to maintain a strong gripping
effect of metal strip 3 onto plate 4, above metal strip 3 a further elastic element
5 is provided, which is elbow-shaped and secured at one end to the body 1 by the fastening
means 2, and resting flexibly onto the metal strip 3 at the other end.
[0007] In the area where it engages the elastic element 5, the flexible metal strip 3 is
provided with a stiffening metal band 6.
[0008] Further, in this same position the end of a control lever L is connected, cantilever
projecting backward and ending with a control member L1 equipped with a suitably shaped
cam surface, so as to co-operate with a loom engaging system (not shown).
[0009] Finally, the pressure that can be exerted by the elastic element 5 onto the flexible
metal strip 3 can be adjusted by means of an adjusting block 7 that can be shifted
longitudinally along the gripper body 1 to deform the element 5 to a higher or lower
degree, and thus determine a higher or lower elastic load onto the metal strip 3.
[0010] Operation of this type of gripper provides that, as known, the weft yarn is grasped
between the metal strip 3 and the plate 4, and here retained by the gripping action
exerted by the elastic element 5. When the gripper reaches the position in which the
weft yarn must be released, the surface L1 of the control lever L touches an engaging
element integral with the weaving loom (the so-called gripper opener) which causes
the lowering thereof, in the direction of arrow F in fig. 1. This causes the metal
strip 3 to bend, against the spring thrust of the element 5, resulting in disengagement
from the plate 4 and release of the weft yarn.
[0011] This type of gripper has some drawbacks.
[0012] First of all, as it can be noticed, the vertical overall dimensions of the mechanism
illustrated are remarkable, because all control and adjustment members are located
above the working surface of the metal strip 3 with the plate 4.
[0013] Furthermore, it must be considered that, due to this specific design and its overall
dimensions, the metal strip 3 and the elastic element 5 are linked to the gripper
body 1, through the fastening means 2, in a rather backward position (compared to
the gripper feed direction A). This would imply that the theoretical fulcrum point
of the metal strip 3, coinciding with the point of constraint, is extremely recessed
in relation to the engaging area with the plate 4, resulting in the fact that opening
of the gripper would not occur promptly and to the desired degree. Therefore, according
to the prior art, a bearing island 8 is provided, located between the working position
of the metal strip 3 on the plate 4 and fastening/connecting means 2, near to but
backward of the connecting position of the control lever L. By choosing the appropriate
stiffening element 6 and the shape of flexible metal strip 3, it is hence possible
to move forward the actual fulcrum point of the metal strip itself, i.e. at the back
edge 8a of bearing island 8.
[0014] Therefore, a force applied in direction F to the end L1 of lever L can be broken
up - shifting it at the bearing island 8 - into a shear force onto metal strip 3,
which tends to maintain the same adherent to island 8, and a torque that tends to
rotate (by bending) metal strip 3 around rear edge 8a of island 8, producing the desired
amount of deformation.
[0015] However, this layout introduces undesired strains and further friction in the gripping
mechanism, which affect operation effectiveness.
[0016] It is therefore an object of the present invention to supply a gripper of the type
equipped with a flexible gripping metal strip which has an improved and optimised
layout, both in terms of the vertical overall dimensions and in terms of operation
effectiveness.
[0017] Such object is achieved by means of a gripper as described in its essential features
in the attached main claim.
[0018] Other inventive aspects of the system and method are described in the dependent claims.
[0019] Further features and advantages of the gripper according to the invention will be
apparent from the following detailed description, given as an example and taken in
conjunction with the annexed drawings, wherein:
[0020] fig. 1 represents, as already mentioned, a partially-interrupted elevation side view
of a prior art gripper;
[0021] fig. 2 is an elevation side view of a gripper according to the invention; and
[0022] fig. 3 is a plan top view of the gripper depicted in fig. 2.
[0023] A gripper comprises, in a manner known per se, a main body 101, intended to be mounted
over a gripper-mounting strap (not shown), onto which a flexible metal strip 103 is
attached through fastening means 102, which is capable of grasping a weft yarn (not
shown), together with a plate 104 attached to the gripper body 101.
[0024] Above the metal strip 103 an elastic, elbow-shaped pressure metal strip 105 is further
provided, itself attached by an end to the gripper body 101 through the fastening
means 102.
[0025] Between the pressure metal strip 105 and the gripping metal strip 103 a shimming
106 is preferably provided, intended to transfer the action of the former onto the
latter and to determine static deformation of the pressure metal strip 105 in terms
of its distance from the gripping metal strip 103: a sort of leaf spring is therefore
created which increases the pressure exerted by the gripping system onto the weft
yarn.
[0026] According to the invention, fastening means 102 are provided on a small shelf 110,
integral with the gripper body 101 and cantilevered from its side, at a certain height
from a mounting base 101' capable of securing the gripper to the gripper-mounting
strap.
[0027] Furthermore, a control lever V is provided, secured at one end to a point P connecting
it to the metal strip 103, near the shelf 110, and then cantilever projecting backwards,
underneath the shelf, ending with a control member V
1.
[0028] The curved design of the lever V, well recognisable in fig. 2, allows to let the
main part of the lever pass below the shelf 110, despite positioning the control member
V
1 above it, so that it may properly engage with the gripper-opening mechanism integral
with the weaving loom.
[0029] The functioning of the gripper according to the invention is similar to that known
in the field. The elastic metal strip 105 in fact keeps constantly under pressure
the gripping metal strip 103 resting on the fixed plate 104, so as to securely grasp
the weft yarn. At the opening point of the gripper (at the loom end, for a drawing
gripper), the control member V
1 of the lever V touches a suitable engaging element (not shown) which pushes it towards
F. This push translates - in the connecting position P - into a modest shear strain
onto the metal strip 103 and a torque (obtained as a multiplication of the push times
the arm of lever V) which tends to bend the metal strip 103 upwards, thus opening
the engagement with the fixed plate 104 and releasing the weft yarn retained between
them.
[0030] The original design and layout of these members, positioned both above and below
the working plane of the metal strip 103 and of the plate 104 (i.e. the plane where
the weft yarn is gripped), produces an overall vertical limitation of the overall
dimensions, achieving a first desired object.
[0031] Furthermore, as is apparent, the fulcrum point of the metal strip 103 - essentially
coinciding with the point of constraint on the shelf 110 (for example the front fastening
screw 111) - is sufficiently forward in relation to its position of co-operation with
the fixed plate 104: hence further devices or arrangements are not necessary to differently
determine the fulcrum point, which serves to avoid the frictions and functioning inefficiencies
present in the prior art, thus achieving another desired object.
[0032] However, it is understood that the scope of the invention described above is not
limited to the specific embodiment illustrated here, but that it extends to any other
changes and variants which are within the reach of any skilled person in the art.
[0033] In particular, although for convenience reference has always been made to a drawing
gripper, the teachings offered here can be similarly applied to a carrying gripper
also.
1. Gripper for a weaving loom, of the type comprising a gripper body (101), intended
to be secured to a gripper-mounting strap, onto which a fixed plate (104) and a flexible
gripping strip (103) are mounted, capable of co-operating with each other to retain
a weft yarn, said gripping strip (103) being pushed onto said fixed gripping plate
(104) through elastic means (105), and furthermore a control lever (V) being provided,
secured at one end at a connecting point (P) to said gripping strip (103) and comprising,
at its other end, a control member (V1) capable of co-operating with an engaging element integral with the weaving loom,
characterised in that said gripping strip (103) is secured at one end to a supporting shelf (110) laterally
cantilevered to a side of said gripper body (101) and in that said control lever (V) is attached underneath to said gripping strip (103) and extends
backwards below said shelf (110) for a relevant portion of its length (110).
2. Gripper as claimed in claim 1), in which said control lever (V) is so shaped that
the control member (V1), when inactive, is located above and behind said shelf (110).
3. Gripper as claimed in claim 1) or 2), in which said flexible gripping strip (103)
is completely cantilevered, no other intermediate contact points being provided in
its portion between said shelf (110) and said fixed plate (104).
4. Gripper as claimed in claim 1), 2) or 3), in which said elastic means (105) are in
the shape of a metallic lamina attached to said shelf (110), elbow-shaped and supplying
an elastic thrust against said gripping strip (103).
5. Gripper as claimed in claim 4), in which a shimming (106) is provided between said
elbow-shaped metallic lamina (105) and said gripping strip (103), so as to determine
a sort of leaf spring element.