The present invention relates to a cable tie and to a method for producing a cable tie.

In particular, the present invention relates to a cable tie made of plastic material of the type comprising: a ribbon, i.e. a strip having an elongated flat shape, and a strip locking head stably connected to an end of the strip and comprising, in turn, a structure defining a strip locking passage, and strip locking means which are arranged adjacent to the strip locking passage, so as to allow the coupling of a free end of the strip in the locking passage in a first direction, and prevent the extraction of the strip from the locking passage in a second direction opposite to the first direction.

In particular, the strip locking means typically comprise a tooth or metallic locking plate, which is driven/fixed into the locking head by means of an ultrasound fixing/welding process so as to protrude into the locking passage.

In the production of cable ties of the type described above, it is known the need to improve the mechanical performance of the cable tie while maintaining the dimensions thereof unchanged in order to increase the traction forces which can be exerted on the tie during the step of wiring, e.g. by means of automatic or semi-automatic wiring guns, but ensuring however the integrity and hold of the tie itself during such an operation and upon the completion of the same.

Indeed, studies carried out by the applicant demonstrated that the cable ties of the type described above, being about 1.05 mm thick and about 3.5 mm wide; about 1.2 mm thick and about 4.5 mm wide; about 1.4 mm thick and about 7.5 mm wide, are adapted to be ripped and/or torn, i.e. are subject to collapsing and uncoupling of the strip from the locking head, when the strip itself is subjected to a traction force opposite to the locking force exerted by the metallic plate on the strip and equal to about 200 Newton, 400 Newton and 650 Newton, respectively.

Indeed, from the aforesaid studies, it arises that the following technical drawbacks occur by applying a traction force higher than the threshold limits indicated above on the strip of the above-described ties:

• shearing/tearing of the strip by the locking plate;
• plastic deformation of the strip, with consequent loosening of the locking of the tie on the objects;
• deformation and/or rotation of the metallic plate about its fixing point on the locking head, with consequent opening of the tie.

WO2004044871 discloses a tie-type security seal comprising a body of thermoplastic material with a passage therethrough, a metallic insert element that is fixed in the passage and has at least one opening therewith, as well as a locking tooth. An elongated strip of thermoplastic material is integral, at one end, with the body and has another free end for insertion through the passage in a first direction where it is locked by the tooth against removal from the cavity in the opposite direction, the body and strip having been manufactured by a plastic injection operation.

EP1258432 discloses a two piece cable tie having an improved metal locking device anchoring system wherein the cable tie includes a strap including a first end and a free end and a locking head secured to the first end of the strap that defines a strap accepting channel in the head having a strap entry end and a strap exit end. The locking head further includes a metal locking device receiving cavity adjacent to and open toward the strap exit end of the locking head and a mounting slot having an inner support wall, an outer support wall and a support slot communicating the mounting slot with the receiving cavity.

The applicant conducted an in-depth study with the objective of identifying a solution which specifically allows to:

• make a cable tie structured so as to improve the mechanical performance of the known ties, so as to ensure integrity and hold thereof when subjected to traction forces higher than those shown above;
• provide a method for making a cable tie, which method is simple and rapid to be implemented and which meets the aforesaid needs.

It is thus the object of the present invention to provide a solution which allows to achieve the objectives indicated above.

This object is achieved by the present invention in that it relates to a cable tie and to a method for producing a cable tie, as defined in the appended claims.

The present invention will now be described with reference to the accompanying drawings, which show a non-limitative embodiment thereof, in which:

• figure 1 is a plan view of a cable tie made according to the present invention;
• figure 2 is a perspective bottom view of a portion of the cable tie shown in figure 1;
• figure 3 shows an enlargement of the portion of the cable tie, in which the locking insert incorporated in the locking head is shown with a dashed line;
• figure 4 is a longitudinal section I-I of a portion of the cable tie shown in figure 2;
• figure 5 is a cross section taken along II-II of a portion of the cable tie shown in figure 2;
• figure 6 is a perspective view of the locking insert; whereas
• figures 7-9 schematically show a forming mould for the cable tie, in an equal number of operative steps of the injection molding procedure included in the method provided by the present invention.

With reference to figures 1-5, number 1 indicates as a whole a cable tie structured so that, in use, it is operable to be closed as a loop to bind/fix objects to one another, such as for example electric wires, tubular pipes or similar elements.

Cable tie 1 comprises a flexible ribbon having an elongated flat shape, i.e. a strip. 2, and a strip locking head 3 stably connected to an end of the strip 2 and comprising a structure defining a strip locking channel, i.e. passage 4, and strip locking means which are arranged adjacent to the strip locking passage 4, so as to allow the coupling of strip 2 in the strip locking passage 4 in a first direction K1, and prevent the extraction of strip 2 from the locking passage 4 in a second direction K2 opposite to the first direction K1.

In the example shown in figures 1 and 4, strip 2 extends along a first longitudinal axis A and has a predetermined thickness s.

Strip 2 has a rectangular elongated shape, a distal end 2a stably fixed to the body of the strip locking head 3, and a free end 2b shaped so as to be coupled, in use, to the locking head 3.

With reference to figure 4, the strip locking head 3 centrally has a through opening/ locking channel, i.e. locking passage 4 having an inlet portion 4a, within which the free end 2a of strip 2 is able to be engaged, and an outlet portion 4b, from which the free end 2b of strip 2 is adapted to protrude when strip 2 is engaged in the locking passage 4.

In the examples shown in the accompanying figures, the locking channel/passage 4 extends along a second axis B substantially orthogonal to the first longitudinal axis A, has a transversal portion substantially complementary to the transversal portion of strip 2, preferably, but not necessarily, rectangular and is developed on a middle line M orthogonal to the first axis A.

The strip locking means of the strip locking head 3 comprise a locking insert 5, which is provided with an annular plate 6 stably incorporated in the body of the strip locking head 3 between the inlet portion 4a and the outlet portion 4b of the locking passage 4.

The locking insert 5 is further shaped so as to have a pair of fins/teeth indicated hereinafter as flexible/elastic locking plates 7, which stick out from the inner edge of the annular plate 6 towards each other so as to at least partially protrude within the locking passage 4.

The locking insert 5 is further shaped so that the locking plates 7 are aligned with each other and with the longitudinal axis A so that, in use, when strip 2 is engaged in the locking passage 4, the two free ends 7a of the locking plates 7 abut on the two larger faces/surfaces 2c of strip 2, so as to allow the strip to slide within the locking passage 4 in the first direction K1, while clamping the larger faces/surfaces 2c of strip 2 when a traction force towards the second direction K2 is applied thereon.

The locking insert 5 is interposed within the locking head 3 between a lower discoid potion 3a and an upper discoid portion 3b, both shaped so as to centrally have the inlet portion 4a and the outlet portion 4b of the locking passage 4, respectively.

The fins or locking plates 7 of the locking insert 5 are arranged on opposite sides of the middle line M, on respective planes, which are inclined with respect to the second axis B of the locking passage 4 and which intersect at the outlet portion 4b of the locking passage 4.

The strip locking head 3 is further shaped so as to have a pair of protrusions 8 within the inlet portion 4a, underneath the locking plates 7, each protrusion having a saw toothed end 8a arranged in contact with a respective plate 7 and defining, along with the plate 7 itself, a stop ratchet 12 capable of preventing the backward motion of strip 2 within the locking passage 4 in the second direction K2.

In the example shown in figures 1-5, the locking insert 5, i.e. annular plate 6 and plates 7 of the cable tie 1 are advantageously made of flexible, elastic metallic material, while the body of the locking head 3 and the strip 2 are made of plastic material or the like, such as for example thermoplastic material.

In particular, the locking insert 5, i.e. annular plate 6 and plates 7 may be obtained by means of a stamping/shearing process of a small plate made of metallic material.

The upper discoid portion 3b of the locking head 3 has two seats 10, which are arranged on opposite sides of the middle line M over the two saw toothed ends 8a of protrusions 8. and are dimensioned so that each accommodates a tooth or locking plate 7 therein.

Each seat 10 is obtained on the upper discoid portion 2b so as to be closed at one end towards the outer peripheral edge of the upper discoid portion 2b and open at the top and at the opposite end, so as to communicate with the outlet portion 4b of the locking passage 4. Each seat 10 is further dimensioned so as to allow the locking plate 7 to partially bend inside, so as to space apart the free end 4a and the free end 4a of the other locking plate 7 when engaging strip 2 in the strip locking passage 4.

In the example shown in figures 1-5, each protrusion 8 extends within the strip locking passage 8 parallel to axis B, has a substantially rectangular cross section, and is dimensioned to have a transversal width with respect to the second axis B smaller than the width of the corresponding seat 10. Each protrusion 8 is further dimensioned so as to have a transversal width smaller than or equal to the width of the respective locking plate 7.

With reference to the example shown in figures 4 and 6, the free ends of the locking plates 7 advantageously have square edges and at least partially protrude into the locking passages 8 so as to have a distance d which approximates by defect the thickness s of strip 2.

In the example shown in figure 6, each locking plate 7 is inclined with respect to the laying plane of the annular plate 6 by an angle α between 85 and 120°. Each locking plate 7 is preferably inclined with respect to the annular plate 6 by an angle of 90°.

In the example shown in figure 3, the locking head 2 has a transversal section of circular/elliptic shape, while the locking insert 5 is shaped so as to have an outer peripheral edge of substantially circular/elliptic shape having dimensions which approximate by defect corresponding dimensions of the locking head 3, so that the latter completely contains the locking insert 5 therein.

In the example shown in figure 1, the free end 2b of strip 2 has a substantially triangular shape and has two rectangular cavities on the larger surfaces 2c, having a width which approximates by excess the width of the blocking plates 7.

The method for producing the above-described cable tie 1 is described below.

The method essentially includes implementing an injection molding procedure for the tie in which the locking insert 5 is incorporated in the strip locking head 3.

With reference to figures 7-9, the method includes arranging a tie forming mold 15, which comprises two metallic casings 16 and 17, which are intended to abut against each other and are structured so as to form, in the middle of the contact surface between the casings 16 and 17, at least one closed impression 18 shaped so as to negatively trace the shape of one or more cable ties 1 of the above-described type.

The method essentially includes:

• cyclically abutting the metallic casings 16 and 17 against each other by means of a casing actuation press (not shown), so as to cyclically form the closed impression 18 which negatively traces the shape of the cable ties 1 to be produced; and
• at each cycle, injecting plastic material in liquid state into the closed impression 18 of the forming mould 15 in a controlled manner through an injection device (not shown).

With reference to figures 7-9, the method for producing cable ties may include:

• opening the forming mould 15 so as to separate the two casings 16 and 17 (figure 7) from each other;
• positioning the locking insert 5 in the portion of the impression intended to form the strip locking head 3; the locking insert 5 may be positioned in the impression by means of an external handling member 45 (figure 8);
• abutting the casings 16 and 17 against each other, e.g. the movable casing towards the fixed casing, so as to close the forming mould 15; in particular, casings 16 and 17 may comprise a fixed casing and a casing moving from and to the fixed casing;
• injecting the plastic material in liquid state into the closed impression 18 so as to stably embed/incorporate the locking insert 5 within the locking head;
• separating the casings so as to open the forming mould;
• extracting cable tie 1 from the forming mould 15 by means of the external handling member 45 (figure 9).

From the above, it is apparent that the method for producing cable ties may include an internally shaped mould so as to have a plurality of impressions, i.e. a comb of impressions arranged side-by-side so as to produce, at each injection cycle, a plurality of cable ties (figure 8). Here, at each injection cycle, a die (i.e. a strip of locking inserts 5 dimensioned so as to place each locking insert 5 at the portion of a corresponding impression intended to form the strip locking head 3) may be positioned in the mould.

The advantages that the present invention allows to obtain are apparent from the above description.

Firstly, the presence of protrusions with saw toothed ends inside the locking passage and underneath the teeth or locking plates cancels out any possible deformation and/or rotation of the plate about its fixing point on the locking head, thus ensuring the tie holding.

Furthermore, the structure of the locking insert in which the annular plate "embedded" in the locking head and its opposite metallic plates are used, allows the traction force which can be exerted on the strip when wiring to be significantly increased.

Moreover, in addition to advantageously eliminating a step of the production process which includes the sharpening of the ends, the use of plates with free ends having square, dull edges strongly reduces the possibility for the plates to cut the strip when locked.

In this case, the tests carried out by the applicant on the above-described tie proved that ties being about 1.05 mm thick and 3.5 mm wide; about 1.2 mm thick and 4.5 mm wide; about 1.4 mm thick and about 7.5 mm wide, may be subjected to a traction force of about 270 Newton, 400 Newton and 850 Newton, respectively.

Additionally, the method for producing the tie is highly rapid and simple as the incorporation of the locking insert in the tie occurs when molding the same, and does not thus require any additional step of fixing/welding the teeth onto the locking head.

It is finally apparent that changes and variations may be made to the tie and method described and shown above, without departing from the scope of the present invention as defined by the appended claims.