CABLE TIE

Description

TECHNICAL FIELD

The present disclosure relates to the field of cable ties, in particular environmentally friendly and tamper evident cable ties.

BACKGROUND

Cable ties (also referred to as zip ties or plastic straps) have long been used to secure cables and other articles together.

Cable ties are used in large quantities and many of them eventually end up in the environment after use and present a danger for animals that can get entangled or swallow them. Further, the commercially available cable ties are typically formed from plastic materials having large carbon footprint.

WO2022216202A1 discloses a cable tie comprising a cord comprising cellulosic fibers and a locking head fixedly attached to the cord, said locking head being adapted to receive the second end and retain the cable tie in a closed loop configuration wherein said locking head defines a walls that encircles a passage having an inlet and an outlet and comprises a metal blade that extends into the passage for engaging the cord and which is arranged to allow displacement of the cord in a first direction towards the outlet while preventing displacement of the cord in a second direction towards the inlet.

To be regarded as an easy-to-use alternative to conventional plastic cable ties, the cable tie should preferably provide a high strength and locking force, allowing it to be used in a variety of applications, while at the same time being easy to handle.

SUMMARY

The present inventors have realized that the configuration of the cord used in the cable tie may impact the strength and locking force of the cable tie, as well as its usability.

An objective of the present disclosure is to provide a cable tie of reduced environmental impact. Another objective is to provide a cable tie that is strong, non- releasable and tamper evident. A further objective is to provide a cable tie with improved usability.

To meet the first objective, a cable tie comprising a paper cord is provided. To meet the second and third objectives, the cord comprises a paper strip twisted along its length, the number of turns of the twisted paper strip being chosen such as to achieve a strong cord and good locking force between the cord and the locking head, while requiring a low enough force for manually inserting the cord into the locking head. By providing a cord which requires a low force for inserting the cord into the locking head, the usability of the cable tie may be improved.

Accordingly, the present disclosure provides a cable tie comprising:

• • a cord having a first end and a second end, and
  • a locking head fixedly attached to the first end, said locking head being adapted to receive the second end and retain the cable tie in a closed loop configuration, wherein the locking head defines (a) wall(s) that encircles a passage having an inlet and an outlet, and comprises a protrusion that extends into the passage for engaging the cord and which is arranged to allow displacement of the cord in a first direction towards the outlet while preventing displacement of the cord in a second direction towards the inlet, and wherein the cord comprises a paper strip twisted along its length, the number of turns per meter of the twisted paper strip being 55-75.

By using a cord comprising a twisted paper strip, the number of turns of the twisted paper strip being 55-75, a cable tie with improved properties regarding locking strength and usability may be achieved.

In addition to being more environmentally friendly than conventional plastic cable ties, the disclosed cord may provide a high strength, and a high locking force in the disclosed locking head. Furthermore, in contrast to conventional plastic straps, there is no need form “ridges” or “pockets” in such a cord to facilitate locking, since the protrusion interacting with the surface of the paper strip cord provides enough locking force.

A paper strip twisted to 55-75 turns per meter has been found to produce a cord which may achieve good locking strength and usability. A cord with fewer turns per meter may provide a cord which is prone to untwisting and which comprises gaps along its surface preventing the cord from being pushed through the locking head with little effort. On the other hand, a cord with a higher number of turns/meter may generate quality problems as the cord becomes more prone to untwisting and bending due to tensions in the cord, and which may comprise too many deviations from an average diameter to allow for the cord to be pushed through the locking head with little effort. Too much deviations in the diameter may also lead to a more uneven locking force along the cord.

By providing a cord having few deviations from the average diameter, the usability of the cable tie may thus be improved, as pushing of the cord through the passage is facilitated. This may be especially important in situations where an operator is to attach a large number of cable ties under a certain period of time.

It has further been observed that the most beneficial number of turns/meter is the same regardless of the cord diameter. Efficient manufacturing of the cable tie may thus be achieved.

To facilitate manual insertion into and through the passage, the second end may be flattened. Such a flattened second end may be provided with grooves. Such grooves improve the grip when pulling the cord through the passage. The direction of the extension of the grooves is preferably substantially perpendicular to the longitudinal direction of the cord. The thickness of the flattened second end may for example be 0.60-1.00 mm, such as 0.70-0.95 mm, such as 0.75-0.90 mm. The width of the flattened second end may for example be 2.7-3.2 mm. A ratio of the thickness of the flattened second end to a diameter of the cord may be 0.37-0.54.

In an embodiment, the number of turns per meter of the twisted paper strip is 60-70.

In an embodiment, the number of turns per meter of the twisted paper strip is 63-68.

In an embodiment, the protrusion is a blade, such as a metal blade.

A blade, such as a metal blade, may efficiently prevent the cord from being pulled back out from the passage. Furthermore, the use of such a blade may be especially beneficial for a cord in accordance with the present disclosure, as the twisted paper strip may provide a cord which is resilient enough in a radial direction to allow for the cord to be gripped by the blade, while still being durable enough to prevent tearing, even when the blade is a flat metal blade.

In alternative embodiments, other shapes and materials of the protrusion could be used, such as a plastic tooth extending into the passage.

In one embodiment, the metal of the metal blade is steel, preferably stainless steel, such as austenitic stainless steel. A suitable example of an austenitic stainless steel is EN 1.4310.

In an embodiment, the passage has a central axis and the angle between the direction of the extension of the blade and the central axis is 47°-62°, such as 50°-59°, such as 52°-57°.

By arranging the blade at an angle, insertion of the cord into the locking head may be facilitated, while at the same time increasing the locking force. The blade may be allowed to move and/or flex to a certain degree when being subjected to a force in a direction from the outlet and towards the inlet of the passage.

The metal blade typically has an embedded portion and an extending portion. In such case, the blade may be embedded in a body portion of the locking head.

In an embodiment, the diameter of the cord is 1.0-8.0 mm, such as 1.5-5.0 mm, such as 1.75-2.10 mm, such as 1.80-2.00 mm. This diameter of the cord has been shown to provide a versatile cable tie which is strong enough for the most common applications, while not being over-dimensioned. For example, the cable tie may be used in applications where space is limited, whereby a larger diameter would be unsuitable. However, in some applications, a larger or smaller diameter of the cord may be preferred.

When the diameter is 1.75-2.10 mm, the width of the untwisted paper strip is preferably 28-35 mm. When the diameter is 1.80-2.00 mm, the width of the untwisted paper strip is preferably 30-33 mm.

In an embodiment, the diameter is defined as the mean value of at least 10 diameter values measured at different points distributed along the length of the cord. As discussed below, the cord may be flattened at the second end. If so, the flattened part is excluded from the diameter measurement(s). A vernier caliper may be used for the diameter measurement(s).

Alternatively and/or additionally the diameter d may be defined as the mean value of a larger number of diameter values, such as at least 100 diameter values, measured on a plurality of different cable ties from the same batch.

When the at least 10 diameter values have been measured, a coefficient of variation can be calculated. In an embodiment, the coefficient of variation is less than 5%.

In an embodiment, the stretch at break of the cord is 2.0%-6.0%, such as 2.5%-4.0% when measured according to ISO 2062:1993.

In an embodiment, the stretch at break of the paper strip after untwisting is 1.5%-3.5%, such as 2.0%-2.9%, when measured according to ISO 1924-3:2005 in its length direction. The length direction of the strip corresponds to the machine direction (MD) of the paper from which the strip was cut.

The tensile strength of the cord may be 4-80 kg, such as 15-70 kg, measured according to ISO 2062:1993.

In an embodiment, the paper strip is a waxed paper strip.

By coating the outer surface of the paper strip with a wax, such as paraffine, the surface of the cord may be improved with regards to the production. For example, in cases where the paper strip has been coated with wax, no heating is necessary in a pressing operation used to form a flattened second end.

Furthermore, the waxing the paper may protect the machines used for producing the cable tie, by preventing abrasion.

In an embodiment, the paper strip is made of kraft paper.

Hereby, a strong and durable cord may be provided from a commonly available, and environmentally friendly, material.

In an embodiment, the paper strip is made of a paper having a grammage measured according to ISO 536:2019 of 55-85 g/m², preferably 60-80 g/m², such as 65-75 g/m².

It has been discovered that a paper strip with such a grammage is well adapted for being twisted into a twisted paper strip having a high strength and a low number of surface deviations.

In an embodiment, the locking head comprises a body of a biodegradable material, such as a bio composite of a biodegradable and/or renewable polymer and an organic fiber material.

Thus, a more environmentally friendly cable tie may be achieved as compared to conventional locking heads being produced from fossil-based plastic materials.

In one embodiment, the inlet of the passage is funnel-shaped, such as trumpet-shaped.

This may facilitate insertion of the second end into the passage, thus further increasing the usability of the cable tie.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1 is a cross-sectional side view of an embodiment of a cable tie according to the present disclosure.

FIGS. 2a-b schematically illustrates an non-twisted paper strip and a twisted paper strip respectively.

FIG. 3 is a front view from the of a cable tie according to the present disclosure, as seen from the inlet of the passage.

DETAILED DESCRIPTION

With reference to FIG. 1, an embodiment of a cable tie 100 of the present disclosure is described.

The cable tie 100 comprises a cord 101 having a first end 102 and a second end 103. The cord 101 comprises a paper strip 10 twisted along its length. A typical diameter d of the cord 101 may be 2 mm. As will be described in more detail below, the locking head 104 is adapted to receive the second end 103 and retain the cable tie 100 in a closed loop configuration.

The locking head 104 defines a wall 105 that encircles a passage 106. Alternatively, the locking head defines a plurality of walls that jointly encircles a passage 106. In either case, the wall(s) prevent(s) substantial lateral movement of the cord 101 when received in the passage 106.

The passage 106 has an inlet 107 and an outlet 108. The inlet 107 is preferably funnel-shaped, such as trumpet-shaped, to facilitate manual insertion of the second end 103 into the passage 106. To further facilitate the manual insertion, the second end 103 may be flattened.

The locking head 104 further comprises a protrusion 109 that extends into the passage 106 for engaging the cord 101 after receival thereof. In FIG. 1, the protrusion 109 is illustrated as a metal blade attached to the wall 105 of the passage 106. However, in other embodiments the protrusion may comprise other shapes or materials, such as a plastic tooth integrated in the locking head 104.

The arrangement of the protrusion 109 is such that displacement of the received cord 101 in a first direction towards the outlet 108 is allowed (meaning that the loop formed when the second end 103 is received can be tightened) while displacement of the cord 101 in the opposite direction, i.e. a second direction towards the inlet 107, is prevented (meaning that the tie cannot be released without excessive force or destruction). The protrusion 109 may be arranged at an angle between the direction of the extension of the blade 109 and a central axis 110 of the passage 106, For example, said angle a may preferably be 47°-62°, more preferably 50°-59°, most preferably 52°-57°.

FIG. 2a-2b schematically illustrates a paper strip 10 of the present disclosure. The paper of the paper strip 10 is preferably selected such that a cord with high tensile strength and a certain stretchability is obtained in the cord, e.g. a cord with a stretch at break value of 2%-5%.

The paper strip 10 may be made of a kraft paper. The grammage of the paper in the paper strip may be between 60 and 80 g/m² such as 70 g/m². The stretch of break value of the paper strip 10 after untwisting may be 1.5%-3.5%, such as 2.0%-2.9%, when measured according to ISO 1924-3:2005 in its length direction. The length direction of the strip corresponds to the machine direction (MD) of the paper from which the strip was cut. The tensile strength of the paper strip 10 after untwisting may be 6.0-9-5 in the length direction.

In FIG. 2a, the paper strip 10 is illustrated in a non-twisted state. The paper strip 10 has a width w and a length L. The width w of the paper strip 10 may vary depending on the desired diameter of the cord 101. For example, the width w may be 25 mm-40 mm, such as 31 mm-36 mm.

The paper strip 10 may be processed before twisting. For example, the paper strip may be wrinkled and/or folded any number of times. Wrinkling or folding of the cord prior to twisting may increase the strength of the cord 101 and/or provide a cord 101 with less surface deviations. Furthermore, a coating, such as a wax, may be applied to the non-twisted paper strip 10.

FIG. 2b illustrates the paper strip having been twisted along its length L to form the cord 101, or at part of the cord 101. The twisted paper strip in FIG. 2b has been produced by twisting the paper strip 10 55-75 turns along its length L. One turn is provided by turning a first end of the paper strip 10 in relation to a second end of the paper strip 360° around an axis parallel to the extension of the length L of the paper strip 10. A way of determining the number of turns per meter of the cord 101 may be to provide one meter of the cord 101 and twist it at its ends in a direction opposite to the twisting direction, while counting the number of whole turns required to revert to a non-twisted paper strip.

The cord 101 in FIG. 2 has further been flattened at the second end 103 to facilitate insertion of the second end 103 into the inlet 106 of the passage 107. In cases where the paper strip 10 has been coated with wax, such that the cord 101 is formed from waxed paper, no heating is necessary in a pressing operation used to form a flattened second end 103. The tool used for such a pressing operation may have (a) contact surface(s) provided with ridges to form grooves in the flattened second end. Furthermore, the waxing the paper may protect the machines used for producing the cable tie, by preventing abrasion.

A method for manufacturing the cord 101 for the cable tie 100 may thus comprise providing a paper strip 10 and twisting the paper strip 10 55-75 turns per meter, such as 60-70 turns per meter, along its length.

In an optional step, the method may further comprise applying a coating onto the paper strip 10 before the twisting.

FIG. 3 is a front view of the cable tie 100 as seen from the side of the inlet 107 of the passage 106. The cross-section of the passage in FIG. 3 has the shape of a discorectangle, that is, a rectangle with semicircles at a pair of opposite sides. The protrusion 109 extends into the passage 106 from a first wall portion 105a being arranged at a long end of the discorectangle. The gap between the free end of the protrusion 109 and a second wall portion, opposite to the first wall portion, defines the opening through which the cord 101 is to be pulled through. In other embodiments, the cross-section may have other shapes, such an oval shape, a rectangular shape with rounded corners, a circular shape or a completely rectangular shape.