GB2497959A

GB2497959A - Insulator for supporting electric fence wires

Info

Publication number: GB2497959A
Application number: GB1122244.5A
Authority: GB
Inventors: Graham David Harper
Original assignee: HARPER CHALICE GROUP Ltd
Current assignee: HARPER CHALICE GROUP Ltd
Priority date: 2011-12-22
Filing date: 2011-12-22
Publication date: 2013-07-03
Also published as: GB201122244D0

Abstract

The insulator 10 has a formation for supporting a wire 20 and a mounting formation 40 by which the insulator may be attached to a support (60, fig 5). The mounting formation 50 has a forked portion with a pair of limbs 44, 46 extending in spaced apart relation, a first hole 50 extending transversely through a first of said limbs and a second closed hole 52 extending coaxially of the first hole partially through a second of said limbs, from an inner surface of said second limb. A pin 90 of generally cylindrical configuration being of a diameter which is a tolerance fit in the first and second holes, said pin having a radial projection 96 intermediate of its ends and extending beyond the diameter of the first hole, said projection being a force fit through the first hole and being positioned such that when the pin is inserted through the first hole and into the second hole the projection will abut against the inner surface of the first limb to secure the pin in the first and second holes.

Description

Insulators --The present invention relates to insulators and in particular insulators for high security electric fences.

Insulators used to support wires in high security electric fences conventionally have two support fingers for supporting a wire, for example as illustrated in US Patent Specification US 4077611. In use one finger will be located beneath the wire to support the wire, while the other finger is located above the wire to prevent the wire from being dislodged form the lower finger. With this design of insulator it is advantageous that the twD fingers are of the same design, so that the insulator may be used with either of the fingers lowermost.

Such insulators may be provided with a forked formation by which they may be secured to a fence support, a pin or bolt being secured through aligned holes in a pair of spaced apart limbs of the forked portion and through a hole in. the fence support. Currently insulator of this type use a plastic pin made -of similar material to the insulator, for example copolymer polypropylene.

These pins have an enlarged head portion at one end. The other end of the pin is split and has an enlarged portion which tapers towards the end of the pin, to provide a shoulder formation spaced from the end of the pin. The holes in the limbs of the forked portion of the insulator and the fence support are dimensioned such that the tapered enlarged end portion of the pin may be forced through the holes with the split portion of the pin closing together. Once through the holes the split portion of the pin spring apart so that the shoulder portion of the pin engages against the outer surface of the limb of the forked portion of the insulator to oppose retraction of the pin.

With this method of securing the insulator, while difficult, it is possible to retract the pin, by compressing the split end of the pin and either pushing on the split end which extends beyond the limb on one side of the forked portion of the insulator, or levering the head portion of the pin.

Moreover, in order to facilitate insertion of the pin, the hole through one limb of the forked portion of the insulator is normally of greater diameter than that through the other limb. When ihsalling, the larger diameter hole must be identified, so that the pin may be inserted from the correct side.

The present invention provides a means of securing an insulator to a fence -10 post which once fitted cannot be released. -According to one aspect of the present invention, an insulator comprises a formation for supporting a wire and a mounting formation by which the insulator may be attached to a support, the mounting formation comprising a 1 5 forked portion having a pair of limbs extending in spaced apart relation, a first hole extending transversely through a first of said limbs and a second closed hole extending coaxially of the first hole partially through a second of said limbs, from an inner surface of said second limb; and a pin, said pin being of generally cylindrical configuration of a diameter which is a tolerance fit in the first and second holes, said pin having a radial projection intermediate of its ends, the projection extending beyond the diameter of the first hole, said projection being a force fit through the first hole and being positioned such that when the pin is inserted through the first hole nd into * the second hole the projection will abut against the inner surface of the first * limb to secure the pin in the first and second holes.

With the invention disclosed above, the pin does not extend beyond the second limb and is not accessible from the outer surface of the second limb and cannot therefore be pushed out. Moreover the absence of a head formation on the pin prevents the application of leverage to that side of the pin. Preferably the pin is cFmensioned such that when the projection on the pin engages the inner surface of the inner limb, the pin does not extend beyond the outer surface of the first limb..

According to a preferred embodiment of the invention the projection on the pin comprises an annular rib of a diameter which is a force fit through the first hole. Preferably the annular rib decreases in diameter towards the smaller diameter end of the pin to facilitate insertion of the pin.

According to an alternative embodiment, instead of a continuous rib one or a series of angularly spaced projections may extend from the circumferential surface of the pin. . According to a further embodiment one or a series of angularly spaced axially aligned resilient wedge formations may be provided on the pin, to 1 5 engage the inner surface of the first limb, when the pin is inserted.

In order to facilitate insertion of the pin into the first and second holes, the * pin may taper slightly from a diameter that is a clearance fit with the second holes at an inner end, to a diameter which is equal to or a slight interference * 20 fit with the first hole at on outer end. In addition or alternatively, the diameter of the first hole may be slightly greater than that of the second hole. * *.*.

According to a further aspect of the invention, an insu)ator comprises a * 25 formation for supporting a wire and a mounting formation, the formation for supporting a wire having a pair of fingers, the fingers having a first limb * which extends away from the mounting portion and a second portion which extends laterally from the first portion, the second portions of the fingers extending parallel to but in the opposite directions in overlapping relationship, the fingers being offset form one another in directions parallel to and transverse to the second portions, the fingers being. orientated relative to the mountin.g formation such that a wire may pass between the fingers, one finger being disposed beneath the wire to support the wire, while the other finger prevents the wire from being dislodged from the first finger, a U-shaped clip having a pair of parallel limbs is provided for location between the fingers, one limb on either side of a wire supported by the fingers, detent formations being provided on the U-shaped clip for engagement of complimentary formations on the insulator.

The invention is now described, by way of example only, with reference to the accompanying drawings, in which:-Figure 1 is a part sectional plan view of a known insulator showing the means of securing the insulator to a fence support; Figure 2 a side elevation of an insulator in accordance with the present -15 invention; * Figure 3 is a plan View of the insulator ilkistrated in figure 2; S. S Figure 4 is a front elevation of the insulato illustrated in figure 2; S..... * 20

Figure 5 is a sectional plan view of the insulator illustrated in figure 2, *:H showing its attachment to a fence support; S.. *5*S

Figure 6 is a sectional side elevation of the insulator illustrated in figure 2, *..ø - * 25 showing its attachment to a fence support; Figure 6 is an isometric view of the insulator illustrated in figure 2; and Figure 7 is an isometric view of insulators as illustrated in figure 2 mounted on a fence support. -5

The orientation of the various views described above are with respect to the normal orientation of the insulator in use, when the insulator is secured to a substantially vertical fence support.

S Figure 1 shows a known insulator design which is moulded from a suitable plastics material, for example copolymer polypropylene. The insulator 10 has a body portion 1 2 with pair of spaced apart flange formations 14, 16.

A pair of wire supporting fingers 20 extend perpendicularly from the outer face 22 of flange formation 14. The fingers 20 are of U-shape, one limb 24 of each finger 20 lying against the outer face 22 of flange formation 14. The limbs 24, 26 of the fingers 20 tie parallel to one another, the limbs 24, 26 of each finger 20 extending from a base portion 28 of the U-shape towards the other finger 20. The fingers 20 are offset from one another in directions parallel to and transverse to the limbs 24, 26, thereby providing a transverse passage 30 between the base portions 28 of the fingers 20 and inside the outer limbs 26, in which a wire 32 may be located and supported. -A mounting formation 40 extends from the outer face of flange formation * 16. The mounting formation 40 includes a forked portion 42 having a pair * S. * 20 of spaced apart limbs 44, 46, the limbs 44, 48 extending away from the flange formation 16 and parallel to the fingers 20. Axially aligned transverse holes 50, 52 are provided in the limbs 44, 46, adjacent the free edges thereof. t*.. a

* 25 A T-shaped fence support 60 has a Longitudinal channel portion 62 with flange formations 66 extending perpendicularly outwardly from each free edge of the channel portion 62. The forked portion 42 of the mounting formation 40 is adapted to engage the channel portion 62, of the fence support 60, one limb 44, 46 being disposed oh each side of the channel portion 62. A hole 64 of larger diameter than holes 50, 62, is provided in the flange formation 62 ate location appropriate for the mounting of an insulator 10.

A pin 70 made of material similar to insulator 10 engages through the holes 50, 64 and 52, to secure the insulator 10 to the fence sup3ort. The pin 70 has a head formation 72 a one end. The other end of the pin 70 is split having a diametrical slot 74 which extends towards to head formation 72 part way along the pin 70. The split end of the pin 70 has an enlarged diameter portion 76 which increases in diameter from the end of the pin 70 and defines a shoulder formation 78 at the end of the enlarged diameter portion 76 nearest the head formation 72..

The maximum diameter of the enlarged diameter portion 76 of pin 70 is such that it is a force fit through the holes 50 and 52, when the split end of pin 70 is compressed to close the slot 74. The pin 70 may thereby be forced through the holes 50, 64 and 52 to secure the insulator 10 to the fence support 60, the split end of the pin 70 springing apart when the enlarged diameter portion76 clears the outer surface of limb 46, so that the shoulder formation 78 will engage the outer surface of limb 46 to retain the pin 70.

With this construction, the split end of the pin 70, which extends through limb 46, is accessible and may the compressed to close slot 74, so that the pin 70 may then be removed by pushing on the split end or levering against the head formation 72. This is undesirable when used in high security * . S..

* electric fences, when release of the insulator 10 from the fence supportwill -* . allow the wires 32 to be moved apart A further disadvantage of this method of securing the insulator 10 as that in order to facilitate insertion of the pin the diameter of one hole 50, 52 is made to be greater than that of the other hole 52, 50. With this arrangement, in order to ensure that the pin is secured properly, the pin must be inserted from the side with the greater diameter hole 50, 52. This will require close examination of the ihsulator 10 to determine the greater -7 diameter hole 50, 52 before fitting the insulator, thus slowing installation of the insulator.

Figures 2 to 7 illustrate a modification to the insulator 10 described above, the same reference numerals being used for corresponding parts.

As illustrated in figures 2 to 7, the portions of the limbs 44 and 46 surrounding holes 50, 52 are thickened locally by projections 80, 82 extending from the outer surfaces of limbs 44, 46, respectively. Hole 50 extends through limb 44 and projection 80, while hole 52 extends only part way through the Limb 46 and projection 82, from the inner surface of limb 46.

A tapered pin 90 has an inner end 92 with a diameter slightly small than the 1 5 internal diameter of hole 52 and an outer end 94 of equal or slightly greater diameter than the internal diameter of hole 50. An annular rib formation 96 is provided on the pin 90 intermediate of the ends 92, 94. The rib formation 96 is spaced from the inner end 92 by a distance smaller than the distance between the closed end of hole 52 and the inner surface of limb 44, so that when the pin 90 is inserted, the outer edge of rib formation 96 will abut *r against the inner surface of limb 44 tO retain the pin 90. The rib formation 96 is spaced from the outer end 94 of pin 90 such that the distance between the outer edge of the rib formation 96 and the outer end 94 is ** 4** * equal to or less than the thickness of limb 44 and projection 80. * . S...

The rib formation 96 has a maximum diameter in ?xcess of the internal diameter of hole 50, so that it is a force fit through hole 50. The rib formation 96 tapers towards the inner end 92 of pin 90 to facilitate insertion of the pin 90 through hole 50, the outer edge of rib formation 96 defining a shoulder formation 98 which will abut against the inner surface of limb 44 when the pin 90 is inserted. -With hole 64 in the fence support 60 aligned with holes 50, 52, the pin 90 may be inserted into hole 50 and the rib formation 96 forced through hole so that the pin 90 engages through hole 54 and into hole 52 and is located fully within the hoLes 50, 52.

When fully inserted in the bores 50, 52. the closed end of hole 52 prevents access to the pin 90 preventing it from being pushed out. Moreover as the pin 90 is fully located in the holes 50, 52, it is not possible to access the pin to pull or lever the pin 90. Abutment of the shoulder portion 98 of rib formation 96 against the inner surface of limb 44 will thereby securely retain the insulator 10 on the fence support 60. Using this means of securing the insulator 10 to the fence post 60, the only way in which the insulator 10 may beremoved from the fence support 60 would be to cut the insulator 10 or drill out the pin 90.

-As illustrated in figure 4 a pair of apertures 110 are provided through the flange formation 14. The apertures 110 are provided centrally of the wire supporting fingers 20 one on either side of the transverse centreline between the base portions 28 of the wire supporting fingers 20. The : 20 apertures 110 are substantially semicircular. * *

A U-shaped plastic clip 11 2 has a pair of limbs 114 of semicircular section * * * * corresponding to the apertures 110. A groove 116 is provided in the outer **.*** * periphery of each of the limbs 114, adjacent their free ends 118. Each *.** limbs 114 is tapered to a point, from the outer edge of the groove 1 16 to the free end 118.

With the insulator 10 described above, a Wire 32 is supported by the insulator 10, the wire 32 passing transversely between the inner and outer limbs 24, 26 of the wfre supporting fingers 20, the wire being supported by the base portion 28 of the lower wire supporting finger 20, the upper wire supporting finger 20 prevents the wire from being disengaged from the lower wire supporting finger 20. The plastic clip 112 is placed with one limb 114 on either side of th.e wire 32 and the free ends 118 are pushed into the apertures 110, until the grooves 11 6 are aligned with the flange formationl4, when the limbs 114 spring apart and flange formation 14 S engages to grooves 116, thereby locking the plastic clip 11 2 and wire 32 in place.

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