GB2476119A

GB2476119A - Cable tie

Info

Publication number: GB2476119A
Application number: GB0921810A
Authority: GB
Inventors: Robert Geraint Evans
Original assignee: Individual
Current assignee: Individual
Priority date: 2009-12-14
Filing date: 2009-12-14
Publication date: 2011-06-15
Also published as: GB0921810D0

Abstract

A cable tie head (1) is in the form of a short rectangular tube with two tubular passageways (60) disposed side by side for receiving opposite ends of a separate tie strap (2) in entrance openings (EO) thereof. Each passageway encloses an integral deflectable locking member (5) which projects away from its entrance opening and engages recesses (7) defining a non-directional rack surface of the tie strap. The resulting tie has the advantage that the tie strap can be supplied on a reel and cut to the required length, reducing waste. In a variant, the locking member has projection/ recess portions formed on an outwardly facing major surface thereof which engage the rack surface.

Description

Tie head, Tie, Tying Kit and Tying Method The present invention relates to a tie head, a tie comprising a tie head and a separate tying strap, a tying kit and a tying method. The invention relates particularly but not

exclusively to the field of cable ties.

Cable ties conventionally consist of a tie head and an integral tie strap (a "tail") which has one free end for insertion in the tic head. The tail has a racking surface with teeth having a sawtooth profile. The head has a short passageway orthogonal to the tail with an integral pawl at an inclination to the passageway axis and arranged to lock against the teeth of the tail when the latter is inserted through the passageway in the direction of the pawl. The sawtooth profile (with the teeth inclined against the direction of insertion) makes the racking surface directional and helps to ensure that the force required to retract the tail from the tie head (typically more than SON) is many times greater than the force required for insertion.

A disadvantage of the conventional cable tie is the predetermined length of the tail, which limits the size of the cable bundle or other member which can be tied and in the case of a relatively small cable bundle results in an excess length of tail. This is wasteful and leads to a requirement for cable ties of different lengths, which can be inconvenient and is somewhat uneconomical.

Ties comprising a tie head and a separate tie strap (which can be of indefinite length and cut to length as required) are known. Thus US 4,377,887 discloses a tie comprising a tie head and a separate tie strap having a non-directional rack surface defined by a row of closely spaced laterally disposed rectangular apertures. By a non-directional rack surface is meant a rack surface which is equally lockable by the locking member of a tie head irrespective of the orientation of the inserted tie strap.

The tie head has a straight passageway which receives the ends of the tie strap in its respective opposite ends, and has internal cantilevered locking members with tangs at their extremities which engage the respective ends of the tie strap with a ratchet action. A disadvantage of the above arrangement is that the relatively short passageway in the tie head must accommodate both free ends of the tie strap, which implies that it must be cut to length quite exactly.

US 4,754,434 discloses a banding clip or tie head having two passageways for receiving opposite ends of a tie strap having a non-directional rack surface defined by a row of rectangular teeth. Each passageway is provided with an external toothed locking member which is deflectable only in the insertion direction. This engages the rack surface with a ratchet action and prevents withdrawal of the tie strap. The passageways are disposed nearly end to end (at an obtuse angle) to accommodate strap ends entering from opposite ends of a large loop extending around the circumference of a duct. The passageways are however mutually offset to allow one end of the strap to be withdrawn through its passageway clear of the other passageway.

This arrangement avoids the disadvantage of US 4,377,887 but has disadvantages of its own. For example it is only suitable for forming ties with a relatively large diameter loop and because the locking members are exposed they can be accidentally or undesirably released from the racking surface to undo the tie. Furthermore the construction is relatively complex.

US 5,544,391 discloses a tie head for use with a smooth-surfaced plastic tie strap, the tie head having passageways for the tie strap disposed side by side and intersected by a transverse V-shaped aperture extending between opposite faces of the tie head. A V-shaped sheet metal paw! is located in the V-shaped aperture and has serrated extremities which extend into the tie strap passageways and bite into ends of a tie strap inserted therein to prevent its withdrawal. However because the V-shaped metal pawl is (necessarily, to enable it to be inserted) accessible through the V-shaped aperture it is not completely secure and moreover the manufacture of the tie head involves the stamping, forming and insertion of a metal piece which adds to the cost.

Similarly US 4,422,217 discloses a tie head for use with a smooth-surfaced plastic tie strap, the tie head having passageways for the tie strap disposed side by side and a sheet metal insert having inclined pawl portions extending into both passageways.

The pawl insert is formed as a cross with one pair of opposite legs constituting the paw! portions and the orthogonal pair of opposite legs acting as retaining portions which hold the insert in a recess formed between the channel portions. Again, the pawl arrangement is accessible and therefore not secure and manufacture involves the stamping, forming and insertion of a metal piece.

An object of the present invention is to overcome or alleviate at least some

disadvantages of the above prior art.

Accordingly, in one aspect the invention provides a tie head having two passageways for receiving respective tie strap ends, said passageways being disposed side by side with adjacent entrance openings and each passageway enclosing an integral deflectable locking member which projects away from its entrance opening and which in use is engageable with the rack surface of a tie strap, separate from the tie head, inserted into the passageway through its entrance opening.

The enclosed integral locking member has the advantage of security and decreased manufacturing cost and the side by side disposition of the passageways leads to further advantages such as the possibility of securing two locking heads back-to-back on connecting tie straps which will become apparent from the detailed description which follows.

Preferably the tie head is a one-piece moulding of plastics material including said integral deflectable locking members. This minimises the manufacturing cost.

Preferably at least one of said locking members has at least one (and preferably two or more) projectionlrecess portion formed on a major surface thereof which faces a wall of the passageway. This projectionlrecess portion can engage a rack surface of an inserted tie strap in use and has the advantages over a locking member whose free end (normally an edge) engages the tie strap of a stronger and more secure locking action.

Preferably said locking members are inaccessible except through their associated passageways, in order to enhance security.

Preferably said locking members extend towards the outermost walls of their respective passageways. This feature has the advantage that when a loop is formed in an inserted tie strap around an object, the resulting outward bending of the tie strap portions projecting outwardly from the entrance openings of the passageways tends to bend the inserted tie strap ends inwardly against the locking members and enhance their locking action.

Preferably the outermost walls of the passageways diverge from each other towards said entrance openings. This feature enhances the above advantage and also enables the tie strap ends to be inserted at an outward inclination which reduces the deflection of the locking members and hence the insertion force.

The invention also provides a tying kit comprising a tie head as defined above in association with at least one separate tie strap or with a continuous length of tie strap material from which tie straps can be cut, said tie strap or tie strap material having a rack surface, whereby in use insertion of tie strap ends through said entrance openings into said passageways deflects said internal locking members, said rack surface and said locking members being so shaped and dimensioned that in use, their resulting mutual engagement prevents retraction of the inserted tie strap ends.

Preferably said tie strap ends have a transverse cross-section which substantially fills the transverse cross-section of said passageways and thereby blocks access to said locking members in the assembled tie. This feature enhances security.

The invention also provides a tie comprising a tie head and at least one separate tie strap having a longitudinally-extending rack surface, the tie head having two passageways for receiving respective tie strap ends, said passageways being disposed side by side with adjacent entrance openings and each enclosing an integral locking member which is deflectable by said racking surface and projects away from the entrance opening of its passageway, whereby in use insertion of respective tie strap ends through said entrance openings into said passageways deflects said internal locking members, said rack surface and said locking members being so shaped and dimensioned that in use, their resulting mutual engagement prevents retraction of the inserted tie strap ends.

Preferably said rack surface is sufficiently non-directional for retraction of an inserted tie strap to be prevented by said mutual engagement, irrespective of which end of the tie strap was inserted.

Preferably said locking members are cantilevered on a common support disposed between said passageways and in use engage an inwardly facing rack surface of at least one inserted tie strap.

In one embodiment, in use, each said locking member is inclined towards the rack surface of an inserted tie strap and a tip thereof abuts an opposing recess/projection surface portion of said rack surface. Preferably the inclination of said recess/ projection surface portion is sufficient to increase the angle of inclination of said locking member on attempting to retract said inserted tie strap end. This feature enhances the locking action.

Preferably, in use there is a spacing between said rack surface and a facing wall of the passageway into which the tie strap end is inserted which allows the strap end to be inserted into said entrance opening at an inclination to said wall which facilitates insertion.

In a preferred embodiment said locking members have projectionlrecess portions shaped and dimensioned to engage recess/projection portions of said rack surface, said projectionlrecess portions having ramp surfaces which in use deflect said locking members during insertion of said tie strap ends and having locking surfaces which abut said recess/projection portions to prevent retraction of the inserted tie strap end.

This feature enhances the locking strength of the tie and also improves security.

Further preferred features are defined in the dependent claims.

Preferred embodiments of the invention are described below by way of example only with reference to Figures 1 to 10 of the accompanying drawings, wherein: Figure 1 is a side elevation, partly in section, of a tie in accordance with the invention; Figure 2 is an end elevation, showing the tie strap in section, taken from the right end of Figure 1; Figure 3 is a plan view of the tie strap utilised in Figure 1, showing the rack surface; Figure 4 is a diagrammatic side elevation of a projectionlrecess portion of a tie strap of the type shown in Figure 3, showing its engagement with the tip of a locking member; Figure 5 is a diagrammatic sectional side elevation showing a further tie in accordance with the invention; Figure 6 is a diagrammatic side elevation of a tie arrangement utilising tie heads as shown in Figure 5; Figure 7 is a side elevation, partially in section, of a further tie in accordance with the invention, having divergent outer passageway walls; Figure 8 is a diagrammatic side elevation, partially in section, of a further tie in accordance with the invention, the locking members being on the outer walls of the passageways; Figure 9 is a diagrammatic end elevation of the tie shown in Figure 8, taken from the right-hand end, and Figure 10 is a diagrammatic view of a tying kit in accordance with the invention.

Referring to Figure 1, tie head 1 is formed as a one-piece moulding of eg glass fibre-reinforced acetal resin and is in the form of a short rectangular tube with a central dividing wall portion 4 and a peripheral outer wall portion 3 which define two tubular passageways 60 of rectangular cross-section disposed side by side for receiving opposite ends of a tie strap 2. The left-hand ends of the passageways form entrance openings EO for receiving tie strap ends which are inserted in an insertion direction I as indicated by the arrow.

Tapered elongate locking members 5 are cantilevered to and integrally formed with the central wall portion 4 and are deflectable by the inserted tie strap ends about centres 6 as indicated in phantom at 5a. The tips of the locking members 5 engage recesses 7 in the form of lateral channels of generally triangular profile. The recesses 7 are regularly spaced apart by corresponding projections of trapezoidal profile and in combination form a non-directional rack surface. As best seen in Figures 2 and 3, this is bounded by raised edge portions 8 whose inner faces bear against the sides of the locking members (Figure 2).

The tie strap 2 is formed into a loop L around eg a cable bundle (not shown) and any attempted retraction of the loop in a retraction direction R is resisted by the locking engagement of the tips of the locking members 5 in recesses 7. Typically, for a tie strap with a rack surface 5 mm in width, the tie will resist a retraction force of at least 20N, preferably lOON or more.

This engagement is shown in more detail in Figure 4, which shows a somewhat generalised version of a recess in which front and rear faces 7a and 7b of the recess are at angles ol and 02 respectively to the top surface of the tie strap 2. Normal N to the rear surface 7b at the point of contact C with the tip of locking member 5 extends below the line joining the centre of rotation 6 of the locking member with the point of contact. Accordingly, aftempted withdrawal of the tie strap 2 in the retraction direction R will tend to increase the downward (clockwise) deflection of the locking member 5 into the recess and will therefore strengthen the locking. For the opposite end of the tie strap 2, the angle 01 will determine the angle of normal N at the point of contact of the locking member with surface 7a. Provided that it satisfies the geometry shown in Figure 4 (or, if it does not, friction between the tip of the locking member 5 and the surface 7a serves to keep the locking member in the recess when the tie strap is pulled in the direction R) this opposite end also will lock satisfactorily in the tie head 1, ie the rack surface of the tie strap 2 will be substantially non-directional.

However for optimum locking, the angles 01 and o2 should be equal as is the case in Figure 1. In that case the rack surface can be said to be completely non-directional.

Conversely a conventional cable tie has a highly directional rack surface with a sawtooth profile in which the angles of the recess surfaces are substantially different, and is designed only to lock the free end of the integral strap.

Figure 5 shows a preferred cable tie comprising a tie head 10 (which like tie head 1 is an integral moulding of glass fibre-loaded acetal resin) and a tie strap 20 looped around a cable bundle W. Like the tie head of Figure 1, tie head 10 has passageways but these are virtually completely filled by the thickness of the tie strap 20. A central dividing wall 40 has locking members 50 cantilevered to a left-hand end thereof such that they are deflectable about centres 6 on insertion of the tie strap ends in the insertion direction T. To facilitate both deflection and locking, the locking members 50 each have three projections 51 on their outwardly-facing major surfaces, these projections being right-triangular in profile with their inclined ramp surfaces facing retraction direction R. Accordingly, insertion of the tie strap ends in direction I forces the projections defined between rectangular profile channels 70 to ride over these ramp surfaces and deflect locking members 50 inwardly towards dividing wall 40. The projections 51 of the strap ends then lock in the recesses 70 as shown and the upright surfaces of these projections then prevent withdrawal in the retraction direction R. Because there is a series of projections 51 on each locking member, at least the left-hand one of which is virtually inaccessible, unwanted release of the tie strap is almost impossible.

Figure 6 shows a tie arrangement utilising four tie heads 1 OA to 1 OC which are as shown in Figure 5, and two tie straps 20A and 20B as shown in Figure 5. However the tie strap ends protrude from the outermost tie heads 1 OA and 1 OD rather than being formed into a ioop. The two inner tic heads lOB and 10 C arc oriented head-to-head so they cannot be separated, and tie head 1 OA is oriented such that it cannot be separated (by being moved to the left) from tie heads lOB and bC.

A post P is fitted between the lengths of strap joining tie heads 1 OA and 1 OB (shown in reduced size purely for ease of illustration of the tie heads). The assembled tie is thus secured to post P. A tree T is shown (in reduced scale) between tie head 1OC and an outer tie head 1OD.

Tie head 1OC can slide to the left along tie straps 20A and 20B as the free grows. Tie head 1 OD provides a restraint to the growing tree.

Figure 7 shows another embodiment in which the entrance openings of the passageways 60 are sufficiently wide to allow the ends of the tie strap 20 to be inserted in direction I at a divergent angle (as shown in phantom) to enable the recesses 7 to slide over the ends of the locking members 5 more easily.

The outer walls of the passageways diverge to match a loop of tie strap formed a cable bundle W. In this configuration the rear faces of the recesses 7 are tilted outwardly so as to confront the tips of the locking members 5 (which project rearwardly from wall portion 4) and ensure secure locking against refraction in direction R. Figures 8 and 9 show a further tie in which a tie head 1000 has locking members 50 with projections 51 similar to those shown in Figure 5 but reversed so as to engage recesses 70 of an outwardly-facing rack surface of a tie strap 20. insertion of the strap ends into passageways 60 in direction I thus deflects the locking members 50 inwardly and subsequent retraction in direction R is prevented.

Finally, Figure 10 shows a reel R of tie strap material 2/20 (ie having the rack surface of tie strap 2 of Figure 1 or of tie strap 20 of Figure 5 to 9) including one tie strap which has been cut off the reel. Tie strap heads 10/100/1000 include two such heads joined by a frangible connection F which can be severed to provide a free tie head for attachment to the cut length of tie strap.

Claims

Claims 1. A tie head having two passageways for receiving respective tie strap ends, said passageways being disposed side by side with adjacent entrance openings and each passageway enclosing an integral deflectable locking member which projects away from its entrance opening and which in use is engageable with the rack surface of a tie strap, separate from the tie head, inserted into the passageway through its entrance opening.
2. A tie head according to claim 1 which is a one-piece moulding of plastics material including said integral deflectable locking members.
3. A tie head according to claim 1 or claim 2 wherein at least one of said locking members has at least one projectionlrecess portion formed on a major surface thereof which faces a wall of the passageway.
4. A tie head according to any preceding claim wherein said locking members are inaccessible except through their associated passageways.
5. A tie head according to any preceding claim, wherein said locking members extend towards the outermost walls of their respective passageways.
6. A tie head according to any preceding claim, wherein the outermost walls of the passageways diverge from each other towards said entrance openings.
7. A tie head assembly comprising two or more tie heads as defined in any preceding claim, said tie heads being joined by a frangible connection to enable successive tie heads to be separated from the assembly for use.
8. A tying kit comprising a tie head as claimed in any of claims 1 to 6 or a tie head assembly as claimed in claim 7 in association with at least one separate tie strap or with a continuous length of tie strap material from which tie straps can be cut, said tie strap or tie strap material having a rack surface, whereby in use insertion of tie sfrap ends through said entrance openings into said passageways deflects said internal locking members, said rack surface and said locking members being so shaped and dimensioned that in use, their resulting mutual engagement prevents retraction of the inserted tie strap ends.
9. A tying kit according to claim 8 wherein said tie strap ends have a transverse cross-section which substantially fills the transverse cross-section of said passageways and thereby blocks access to said locking members in the assembled tie.
10. A tie comprising a tie head and at least one separate tie strap having a longitudinally-extending rack surface, the tie head having two passageways for receiving respective tie strap ends, said passageways being disposed side by side with adjacent entrance openings and each enclosing an integral locking member which is deflectable by said racking surface and projects away from the entrance opening of its passageway, whereby in use insertion of respective tie strap ends through said entrance openings into said passageways deflects said internal locking members, said rack surface and said locking members being so shaped and dimensioned that in use, their resulting mutual engagement prevents retraction of the inserted tie strap ends.
11. A tying kit according to claim 8 or claim 9 or a tie according to claim 10, wherein said rack surface is sufficiently non-directional for retraction of an inserted tie strap to be prevented by said mutual engagement, irrespective of which end of the tie strap was inserted.
12. A tying kit according to claim 8 or claim 9 or claim 11 or a tie according to claim or claim 11, wherein said locking members are cantilevered on a common support disposed between said passageways and in use engage an inwardly facing rack surface of at least one inserted tie strap.
13. A tying kit according to any of claims 8, 9 11 and 12 or a tie according to any of claims 10 to 12, wherein in use, each said locking member is inclined towards the rack surface of an inserted tie strap and a tip thereof abuts an opposing recess! projection surface portion of said rack surface.
14. A tying kit or tie according to claim 13 wherein said rack surface includes transverse channels of substantially triangular profile into one of which said tip projects during use.
15. A tying kit or tie according to claim 13 or claim 14 wherein the inclination of said recess!projection surface portion is sufficient to increase the angle of inclination of said locking member on attempting to retract said inserted tie strap end.
16. A tying kit according to any of claims 8, 9 and 11 to 15 or a tie according to any of claims 10 to 15, wherein in use there is a spacing between said rack surface and a facing wall of the passageway into which the tie strap end is inserted which allows the strap end to be inserted into said entrance opening at an inclination to said wall which facilitates insertion.
17. A tying kit according to any of claims 8, 9, 11 and 12 or a tie according to any of claims 10 to 12 wherein said locking members have projectionlrecess portions shaped and dimensioned to engage recess!projection portions of said rack surface, said projectionlrecess portions having ramp surfaces which in use deflect said locking members during insertion of said tie strap ends and having locking surfaces which abut said recess!projection portions to prevent retraction of the inserted tie strap end.
18. A tying kit or tie according to claim 17 wherein said proj ectionlrecess portions are substantially triangular in profile.
19. A tying kit or tie according to claim 17 or claim 18 wherein said recess!projection portions are substantially rectangular in profile.
20. A tie according to any of claims 10 to 19 wherein a said tie strap is formed into a loop and respective opposite ends thereof are inserted into said passageways.
21. A tie according to any of claims 10 to 19 comprising two such tie heads linked by one or two common tie straps each having ends inserted into mouths of the respective tie heads.
22. A method of forming a tie around one or more members, the method comprising the steps of cutting a continuous length of tie strap material as defined in claim 8 to form at least one tie strap and inserting both ends of the at least one tie strap around said one or more members into entrance openings of one or more tie heads as claimed in any of claims ito 6.
23. A tie substantially as described hereinabove with reference to any of Figures 1 and 2, 5, 6, 7, or 8 and 9 or a tie head substantially as described hereinabove with reference to any of Figures 1 and 2, 5, 7, or 8 and 9 of the accompanying drawings.
24. A tying kit substantially as described hereinabove with reference to Figure 10 of the accompanying drawings.