GB2372282A

GB2372282A - Moulded plastics tie

Info

Publication number: GB2372282A
Application number: GB0104093A
Authority: GB
Inventors: Steven John Blanks
Original assignee: Spirent PLC
Current assignee: Spirent Communications PLC
Priority date: 2001-02-20
Filing date: 2001-02-20
Publication date: 2002-08-21
Also published as: GB0104093D0

Abstract

A one-piece cable tie of plastics material, comprises first and second regions formed respectively of a first plastics material and a more resiliently compressible second plastics material. The first region 31 extends from a strap engaging pawl 19 in a head aperture 11 along the strap 10, where the surface thereof is exposed and carries serrations 12 for engagement by the pawl 19 when the strap is formed into a loop and inserted into the head aperture. The tie is strong, since the harder material of the first region extends continuously all the way around the loop. The second region 32 extends at least along a surface of the strap 10 which faces inwardly when the strap is formed into said loop. The more resiliently compressible material of the second region 32 is compressed slightly against the object(s) about which the tie is applied, thereby enhancing the grip between the tie and the object(s). The tie is formed by an established technique such as twin shot moulding.

Description

MOULDED PLASTICS TIE

This invention relates to a moulded plastics tie for tying cables and the like.

Ties for tying cables are well known. Such ties or socalled cable ties generally comprise an elongate serrated strap having a head at one end defining a head aperture, through which the opposite end of the strap is inserted when the tie is formed into a loop around the object. A pawl in the head aperture engages the strap serrations to prevent the tie from loosening once it has been tightened.

Known cable ties are generally moulded from a strong and hard plastics material, such as nylon, in order that the ties do not break or stretch easily. However, a disadvantage of this is that the hard plastics material of the ties can slip against objects to which they have been applied.

Another disadvantage of nylon ties is that the hard plastics material can damage the objects to which the ties have been applied.

It is preferable for the ties to exhibit some resilience, since this allows the ties to be slightly over tightened and then released, thereby ensuring a more effective grip between the ties and the objects about which they are applied. This also helps to achieve a more effective engagement between the pawl and strap serrations of the tie, since the strap is pulled back slightly once it has been released following over tightening.

Accordingly, a further disadvantage of nylon ties is that they exhibit a minimal amount of resilience and are therefore more difficult to securely fasten about objects.

Ties formed of a softer plastics material are known.

However, such ties are liable to stretch and break easily and are thus unsuitable for many applications.

We have now devised a tie which alleviates the abovementioned problems.

In accordance with this invention, there is provided a

one-piece tie of plastics material, comprising an elongate strap and a head at one end of the strap having means for engaging the strap when the strap is formed into a loop about the object (s) to be tied and engaged with the head, wherein the tie comprises first and second regions formed respectively of a first plastics material and a more resiliently compressible second plastics material, said first region incorporating said strap engaging means and extending therefrom along the strap to a point thereon which is arranged for engagement by said strap engagement means, said second region extending along a surface of the strap which faces inwardly when the strap is formed into said loop.

The tie is formed as a one piece moulding using an established technique known as twin shot moulding whereby the first region is initially formed from a plastics material such as nylon, whereupon the second region is formed from a more resiliently compressible material such as a thermoplastic elastomer.

A tie in accordance with this invention is strong, since the harder plastics material extends from the head along a length of the strip to a point thereon which is arranged for engagement by the head. Accordingly, when the strap is formed into a loop, the harder plastics material extends continuously all the way around the loop. Furthermore, the strap engaging means is formed of the harder material and thus a secure engagement is provided between the strap and the head.

The more resiliently compressible material is compressed slightly against the object (s) about which the tie is applied, thereby enhancing the grip between the tie and the object (s). The compressibility of the material enables the tie to be slightly over tightened. However, once the tie has been tightened it is released and the material recovers its shape slightly, thereby pulling the strap back into secure engagement with the head of the tie.

Preferably the strap comprises at least one point

arranged for engagement by the head, said point being formed of said first material.

Preferably the first region of the tie is serrated and extends along a surface of the strap, the head comprising an aperture for receiving the strap when the strap is formed into a loop and passed through the head aperture, said strap engaging means comprising a pawl disposed in the head aperture for engaging said strap serrations.

In one embodiment, the strap serrations may extend along a surface of the strap which faces outwardly when the strap is formed into said loop.

In an alternative embodiment, the strap serrations may extend along the surface of the strap which faces inwardly when the strap is formed into said loop, the second region extending axially of the strap and projecting outwardly from the strap beyond said serrations.

In the latter case, the serrations preferably extend along a medial portion of the strap, the medial portion being bounded along its length by said second region.

Preferably the second region extends over a surface of the head which faces inwardly when the strap is formed into said loop.

Preferably the strap is flat, the second region preferably extending along opposite side edges of the flat strap.

Preferably said second region does not extend fully to the opposite end of the strap, in order to make the portion of the strap which is initially inserted through the head aperture from the harder plastics material.

The two regions of plastics material are fused together during the moulding process. However, in order to minimise the risk of the regions becoming separated, they are preferably keyed to each other, thereby providing a mechanical interengagement.

An embodiment of this invention will now be described

by way of an example only and with reference to the accompanying drawings, in which : FIGURE 1 is a perspective view of the upper side of a cable tie in accordance with this invention; FIGURE 2 is a perspective view of the bottom side of the cable tie of Figure 1; FIGURE 3 is a perspective view of the ends of the cable tie of Figure 1 when fastened together; and FIGURE 4 is a sectional view along the line IV-IV of Figure 1.

Referring to Figures 1 and 2 of the drawings, there is shown a cable tie formed as a one-piece moulding of plastics material.

The tie comprises an elongate flat strap 10 provided with a series of transverse ratchet serrations 12 on its underside and with a head 14 at one end, the head 14 projecting from the opposite side of the strap 10.

The series of serrations 12 terminates a short distance from the free end of the strap 10, providing a length of strap or so-called tail 13 which is plain apart from the provision of some transverse ridges 15 on one side which serve as finger grips.

The head 14 comprises an inner end wall 16 and an outer end wall 17 and a pair of opposite side walls 20, defining a passage 18 extending through the head, perpendicular to the longitudinal axis of the strap 10.

A resiliently flexible pawl 19 is attached to the inner end wall 16 of the head 14 and extends into the passageway 18 for engaging the strap serrations 12, when the tail 13 of the strap 10 is passed through the passage 18, as shown in Figure 3.

In accordance with this invention, the tie comprises a one piece moulding of two different types of plastics material respectively forming first and second regions 31,32 of the tie.

The first region 31 is formed of nylon material and is formed by introducing the molten nylon into a cavity formed between two mould halves. The two mould halves are then separated, leaving the moulding attached to one half, whilst the other half is reversed or changed to provide a mould having a larger cavity. A softer more resiliently compressible plastics material, such as a thermoplastic elastomer, is then introduced into the cavity surrounding the original moulding.

The completed moulding can then be ejected from the mould.

The first region 31 of nylon material forms a substantial part of the head 14 of the tie, including the side and end walls 16,17, 20 and the pawl 19, and extends from the head 14, longitudinally along the strap 10 to the tail 13, which is completely formed of the first region 31.

The ratchet serrations 12 are provided by the first region 31 as it extends along the length of the strap 10.

The second region 32 extends over the underside of the head 14 and along its corners. Referring to Figure 4 of the drawings, the second region 32 also extends longitudinally along opposite side edges of the strap 10 from the head 14 to the tail 13. The outer ends of the strap serrations 12 preferably lie inwardly of the plane of the underside of the strap defined by the second region 32, as shown in Figure 4.

The first and second regions 31,32 are fused together as a result of the manufacturing process. However, in order to increase the bond between the two regions 31,32 the first region 31 preferably comprises undercut portions, into which the second region 32 extends, thereby providing some mechanical interengagement.

In use, when the tie is formed into a loop around an object and its ends fastened together as shown in Figure 3, the inwardly facing surface of the strap 10 which abuts the object is provided by the second region 32 of softer and more resilient material. Hence, as the strap is tightened, the material compresses, thereby avoiding any damage to the object

caused by the harder nylon material of the first region 31.

Once the tie has been tightened, the tail 13 of the tie is released and the resilient nature of the material compressed against the surface of the object causes the tail 13 of the strap 10 to be pulled back as the material recovers its shape, thereby pulling the pawl 18 into firmer engagement with a strap serration 12. Thus, there is less risk of the tie loosening during use.

The resilient nature of the material in contact with the object about which the ties has been applied also helps to reduce any risk of the tie slipping along the object.

Claims

CLAIMS 1. A one-piece tie of plastics material, comprising an elongate strap and a head at one end of the strap having means for engaging the strap when the strap is formed into a loop about the object (s) to be tied and engaged with the head, wherein the tie comprises first and second regions formed respectively of a first plastics material and a more resiliently compressible second plastics material, said first region incorporating said strap engaging means and extending therefrom along the strap to a point thereon which is arranged for engagement by said strap engagement means, said second region extending along a surface of the strap which faces inwardly when the strap is formed into said loop.
2. A one-piece tie of plastics material as claimed in claim 1, in which the first region of the tie is serrated along a surface of the strap, the head comprising an aperture for receiving the strap when the strap is formed into a loop and passed through the head aperture, said strap engaging means comprising a pawl disposed in the head aperture for engaging said strap serrations.
3. A one-piece tie of plastics material as claimed in claim 2, in which the strap serrations extend along a surface of the strap which faces outwardly when the strap is formed into said loop.
4. A one-piece tie of plastics material as claimed in claim 2, in which the strap serrations extend along the surface of the strap which faces inwardly when the strap is formed into said loop, the second region extending axially of the strap and projecting outwardly from the strap beyond said serrations.
5. A one-piece tie of plastics material as claimed in

claim 4, in which the serrations extend along a medial portion of the strap, the medial portion being bounded along its length by said second region.
6. A one-piece tie of plastics material as claimed in any preceding claim, in which the second region extends over a surface of the head which faces inwardly when the strap is formed into said loop.
7. A one-piece tie of plastics material as claimed in any preceding claim, in which the strap is flat.
8. A one-piece tie of plastics material as claimed in claim 7, in which the second region extends along opposite side edges of the flat strap.
9. A one-piece tie of plastics material as claimed in any preceding claim, in which said first region extends to the free end of the strap.
10. A one-piece tie of plastics material as claimed in any preceding claim, in which said two regions of plastics material are keyed to each other.
11. A one-piece tie of plastics material substantially as herein described with reference to the accompanying drawings.