CABLE TIES

ATTACHES DE CABLES

English Abstract

A cable tie comprises a head and a strap of plastic material. The head has a transverse aperture formed therethrough and contains a separately formed barb. The barb has a head engaging portion and a strap engaging portion extending at least partly across the head aperture. The barb includes a flexure region comprising a pair of opposed cut-out portions each located in a edge of the barb to provide a section of reduced width between the cut-out portions. Each cut-out portion provides a shoulder at the side thereof such that after insertion of the barb into the head the plastic material of the head flows over the shoulders of the cut-out portions to anchor the barb in the head.

French Abstract

Une attache de câble comporte une tête et une sangle en matière plastique. La tête comporte une ouverture transversale la traversant, et contient une barbe formée séparément. La barbe comporte une partie d'enclenchement de tête et une partie d'enclenchement de sangle s'étendant au moins partiellement sur l'ouverture de tête. La barbe comprend une zone de flexion comportant une paire de parties découpées opposées, se trouvant chacune dans un bord de la barbe, afin de fournir une section de largeur réduite entre les parties découpées. Chaque partie découpée offre un épaulement au niveau d'un côté, de telle sorte que, après insertion de la barbe dans la tête, la matière plastique de la tête passe sur les épaulements des parties découpées afin d'ancrer la barbe dans la tête.

Claims

CLAIMS:
1. A cable tie comprising a head and a strap of plastics
material, the head having a transverse aperture therethrough, and
a barb formed separately from the head, the barb having a head
engaging portion a strap engaging portion extending at least
partly across the transverse aperture at an acute angle to the
longitudinal axis of the transverse aperture, and a region of
flexure between the head engaging portion and the strap engaging
portion to allow the strap to be inserted and pulled through the
transverse aperture in a first direction, due to flexure of the
barb, but not in a second direction opposite to said first
direction, the barb flexure region comprising a pair of opposed
cut-out portions each in an edge portion of the barb to provide
a section of reduced barb width between the cut-out portions
relative to the width of the strap engaging portion, each cut-out
portion providing a shoulder at the side thereof remote from the
strap engaging portion, and the plastics material of the head
being such that after insertion of the barb into the head, the
plastics material of the head flows over the shoulders of the
cut-out portions to anchor the barb in the head.
2. A cable tie as claimed in Claim 1 wherein each shoulder
has a portion generally perpendicular to the edge of the barb.
3. A cable tie as claimed in Claim 2 wherein the shoulder
portions are normal to the longitudinal axis of the barb.
4. A cable tie as claimed in Claim 1 wherein each cut-out
portion has an inner edge portion extending parallel to the
longitudinal axis of the barb, the inner edge portions of the two
opposed cut-out portions defining a section of minimum barb width
therebetween.
5. A cable tie as claimed in Claim 4 wherein the section
of minimum barb width extends for between 5% and 15% of the
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length of the barb,
6. A cable tie as claimed in Claim 5 wherein the section
of minimum barb width extends for between 9% and 10% of the
length of the barb.
7. A cable tie as claimed in Claim 5 wherein the barb
is rectangular and the width of the section of minimum barb
width is between 40% and 50% of the width of the strap engaging
portion.
8. A cable tie as claimed in Claim 7 wherein the width
of the section of minimum barb width is 50% of the strap
engaging portion of the barb.
9. A cable tie as claimed in Claim 1 wherein the barb
lies at an angle in the range 30° to 55° to a plane normal to
the longitudinal axis of the transverse aperture.
10. A cable tie as claimed in Claim 9 wherein the barb
angle is 37° ~ 5°.
11. A cable tie as claimed in Claim 9 wherein the angle
is 52° (tolerance +2° and -4°).
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Description

2139'~~~
T&B 1108 pATENT
II~pRCVfi~ENTB zrr CABLE T=ES
Field of the Invention
The invention relates to cable ties . cable tzes are used
for bundling electr~.Gal cables or wizes in order to ease
handling.
HackQround of the Invention
Cable ties generally comprise an elongate strap, commonly
of a plastics material, and a head having an aperture extending
through the head. The head is usually, but not necessarily
formed integrally with the strap at one end thereof. The head
includes a means far engaging the strap which allows the free
end of the strap to be inserted into the head aperture to form
a loop, and pulled through to reduce the loop size, but
prevents the strap from being pulled in a reverse direction to
expand the loop size.
Cable ties are known in which the head and strap engaging
means are molded in one piece. This arrangement eases
manufacture, but imposes a strength limitation because the
z0 engaging means, commonly a pawl, is of a plastics material.
For applications requiring high strength, it has been proposed
to use a metal barb extending into the head aperture at an
angle to allow sliding movement of the strap in one direction
only. The metal barb is embedded in the material of the head.
A cable txe with a metal barb is described in US Patent
Specification No. 3408699, in which a barb, referred to as
prior art, is shown as having a generally rectangular body with
a knife edge formed at on end thereof_ The barb Qf the
preferred embodiments of US Patent Specification No. 3408699
is described as having a weakened area along a J.ine about which
the barb is to flex during arid after xnserti,vn of the strap
into the head apErture. Reducing the force needed to flex the
barb reduces the force needed to insert and pull the strap

~.~3971~
through the aperture. It is stated that weakening can be .
achieved i,n a number of ways, including removal of material
from the barb in its flexure region, making the barb thinner
at or adjacent its flexure region, or by chemical treatment or
annealing. With regard to the possibility of removing material
from the barb at its flexure region, US patent Specification
No. 3408699 shows a barb having a hole cut out of it in the
region where flexure is to take place, but a possibility is
indicated that the sides of the barb may tapered below the
flexure line or that two holes (rather than one) may be placed
at the edge or anywhere along the flexure line.
Summary o~ the Invention
The present invention is concerned with a further
improvement over the disclosure in US Patent No. 3408699 in
cable ties with a barb of metal or other material of similar
mechanical characteristics. More part~.cularly, the present
invention is concerned with improving barb retention in the
head material, as well as improving, in the preferred
embodiment, tolerance of the depth of insertion of the barb
into the head material.
According to the invention, there is provided a cable tie
comprising a head and a strap of plastics material, the head
having a transverse aperture therethrough, and a barb formed
separately from the head, the barb having a head engaging
portion a strap engaging portion extending at least partly
across the transverse aperture at an acute angle to the
longitudinal axis of the transverse aperture and a region of
flexure between the head engaging portion and the strap to be
inserted and pulled through the transverse aperture in a first
direction, due to flexure of the barb, but not in a second
direction opposite to said first direction, the barb flexure
region comprising a pair of opposed cut-out portions each in
2

CA 02139712 2004-06-21
an edge portion of the barb to provide a section of reduced barb
width strap engaging portion, each cut-out portion providing a
shoulder at the side thereof remote from the strap engaging
portion, and the plastics material of the head being such that
after insertion of the barb into the head, the plastics material
of the head flows over the shoulders of the cut-out portions to
anchor the barb in the head.
Each cut-out portion preferably has an inner edge portion
extending parallel to the longitudinal axis of the barb, the
inner edge portions of the two opposed cut-out portions defining
a section of minimum barb width therebetween. The section of
minimum barb width preferably extends for between 5 % and 15%, and
preferably 9% to 10% of the length of the barb.
Each shoulder preferably has a straight outer portion, and
the outer portions may be normal to the longitudinal axis of the
barb.
The barb is preferably rectangular, and the width of the
section of minimum barb is preferably in the range 40% to 60% of
the width of the strap engaging portion. Preferably, the width
of the section of minimum barb width is 50% of the width of the
strap engaging portion of the barb.
The barb preferably lies at an angle in the range 30° to 55°
to a plane normal to the longitudinal axis of the transverse
aperture. A preferred angle is 37° ~ 5°, but a cable tie
embodiment having an angle of 52° (tolerance +2° and -4°)
is also
contemplated.
Brief Description of the Drawincr
By way of example, one embodiment of a cable tie according
to the invention will now be described with reference to the
accompanying drawings, in which:
Figure 1 is a plan view of a cable tie according to the
invention before the barb is inserted;
3

z~397~z
Figure 2 is a side view of the cable tie of figuxe 1;
Figure 3 is a sectional view along the lines IIZ-rII in
figuxe 1 with barb inserted;
Figure 4 is a sectional view along the l~.nes Iv--=V in
Figure 1 w~,th the barb inserted, together with a projected view
of a barb in plan; and
Figure 5 is a sectional view similar to that of figure 4
but with the barb at an alternative angle.
Detailed Descriutibn of the Preferred Embodiments
Figures 1 and 2 show a cable tie 10 of plastics material
such as nylon; it will be appreciated that other plastics
material could be used. The cable tie 10 has an elongate,
flexible strap poxtion 11 and a head portion 12 all molded as
a single piece. Figuxe 1 shows the cable tie 10 before
insertion of a strap retaining barb.
The head portion 12 has a transverse aperture ~.3 thxough
which the strap portion 11 may pass and a channel 14 extending
normal to the longitudinal axis of the transverse aperture 13.
The channel 14 is defined by head side profiles 15, 16 and
includes a tapered recess 17 on the side of the transverse
aperture 13 adjacent the strap portion 11.
The strap portion 11 has a ridged end portion 20,
corrugations being arranged either side of a central lead path
along which a barb may txavel without interruption. A main
part 21 of the strap portion 11 is of a thickness greater than
end portion Z0.
Figures 3 and 4 show the head poxtion 12 with a barb 25
inserted into the plastics material o~ the head portion 12.
As shown in Figure 4, the barb 25 is generally a
reCtangu~.ar section and is made of steel, although othex
suitable materials may be used. The barb 25 has a knife edge
26 formed at a leading edge of a strap engaging portion 27.

A head engaging portion 28 is formed with a leading insertion
edge 2 9 . _. ,'
Cut-out portions 30, ~7. lie between the strap engaging
portion 2S and the head engaging portion 28 and are formed
conveniently by stamping. The cut-out portions 30 and 31 have
portions 32, 33 lying parallel to the side edges of the barb
25 to define therebetween a section o~ minimum barb width. In
the embodiment shown, the parallel port~.ons 32, 33 extend for
between 9% and 10% of the barb length, but this could be
extended to a range of 5% to 15% of the barb length.
As can be seen clearly in Figure 4, when the barb z5 is
inserted .into the material. of the head portion 12 , the head
engaging portion 28 goes completely in to the material of the
head portion Zz and that head portion material flows back over
shoulders 34, 35 on the head engaging portion to anchor the
barb in the head portion 22. The shoulders 34 and 34 both have
outer portions which are straight and perpendicular to the
external sides of the barb.
The barb 25 is arranged at an angle of 37° ~ S' to a plane
normal to the central axis of the transverse aperture 13, the
arrangement being such that when the strap portion 17. is passed
through the transverse aperture 13, the barb is flexed at its
section o~ minimum width defined by the cut-out portions 30,
31 to flex and thereby allow passages of the strap past the
z5 knife edge 26. Once the strap has passed through so that the
barb contacts the figure portion 21 of the strap portion s.l,
any attempt to remove the strap will result in engagement of
the knife edge 26 into the material of the stx-ap portion s7..
Fzgure 5 shows an aitcrnative embodiment in which the barb
25 lies at an angle of 52' (tolerance +2' and -4') to a plane
normal to the longitudinal axis of the aperture 13. The
greater angle of the barb in the F~.gure 5 embodiment eases
insertion of the strap portion 11_
5

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- The barb width between the straight edges of the'cut-out
portions 32, 33 is approximately 50% of the width of the
remainder of the barb. It wil.1 be appreciated that this is a
preferred width and that variations, for example between 40%
and 60% of the width mar be used. A length of the straight
portions 32, 33 may also be varied; the purpose of the
straight portions 32, 33 axe to provide the same. width of barb
at its flexing portion while allowing for some tolerance in the
depth of insertion of the barb into the end portion 12.
1o It will be appreciated that variations in materials of the
cabJ.e tie and the barb, together with variations and
modifications to the embodiment described may be made within
the scope of the invention as defined herein.
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Representative Drawing