GB2059689A - Section insulator - Google Patents

Abstract

Apparatus for the electrically insulating connection (Fig. 1) of two sections (10, 11) of the contact wire of an overhead vehicle supply line has i) two spaced side by side parallel insulating rods (12, 13) of glass fibre reinforced plastics each attached at its ends to a respective metal rod (16); ii) two first crosspieces (18) on the wire (10, 11) and to which the metal rods (16) are connected; iii) clamps (25) joining the wire to one of the first crosspieces; iv) two second crosspieces (22) on the wire and arranged between and spaced from the two first crosspieces (18), one clamp (25) being connected to one second crosspiece (22) and the other clamp (25) to the other second crosspiece (22); and two pairs of skids (26, 28; 26, 28) attached to respective pairs of crosspieces (18, 22; 18, 22). Each respective skid approaches the wire section (10, 11) at one of its ends and is fixed to the wire section by a clamp (27), and extends away from the respective insulating rod (15) at its other end (28). Rods 14 comprise glass fibre reinforced plastics rods 15' and PTFE tube 15. Further constructional provisions are detailed, including materials, alternative embodiment being described w.r.t., Figs. 9 and 12 (not shown). The Fig. 9 arrangement allows collector shoe travel in both directions, includes a different skid arrangement, as does Fig. 12, with vertical plates (e.g. of asbestos), reducing further the risk of arc damage to the rod insulator, and extinction chambers. A silicone rubber tube provided with a spiral groove rather than annular grooves may surround the reinforced plastics rod of the insulator (Fig. 13, not shown). The described arrangements allow mounting and adjusting on the wire before cutting, other objects being detailed. <IMAGE>

Description

SPECIFICATION Apparatus for the electrically insulating connection of two sections of the contact wire of an overhead line This invention relates to apparatus for the electrically insulating connection of two sections of the contactor trolley wire of an overhead line.

Known such apparatus, used as track insulators or phase insulators between two sections of an overhead trolley wire which end at some distance from each other, have numerous disadvantages. They are complicated, expensive and heavy, and cannot be mounted on the wire until it has been cut into the two sections. This separation of the wire before the apparatus is mounted not only makes assembly more difficult because the sections to be joined by the insulator must meanwhile be held in the correct position by a jig, but it also has the more important disadvantage that under these conditions it is generally impossible to prevent formation of one or more kinks in the wire, which could cause the current collector or shoe of a vehicle to lift off the wire when it is moving along it at high speed.

The complicated construction is a disadvantage not only on account of cost, but because of the weight of the structure. If the weight is too great, the shoe receives a jolt as it moves over the insulator, and this jolt will tend to push the shoe downwards and lift it off the wire. The higher the velocity of the'vehicle, the greater is the force of this jolt. Since detachment of the shoe must be avoided and the maximum velocity at which a shoe can travel over the known track insulators and phase insulators without becoming detached is little higher than the travelling velocities customary nowadays, the known insulators are unsuitable for the higher travelling velocities envisaged for the future.

The disadvantages described above are also applicable to the known forms of track insulators in which the insulating bodies are glass fibre reinforced plastics rods, since these also cannot be mounted on the wire until it has been severed at the point of assembly, and these insulators also are relatively heavy.

A first object of this invention is an apparatus for the high tensile strength, electrically insulating connection of two sections of the contact or trolley wire of an overhead line which enables the vehicle to travel at higher speed than is possible with known apparatus.

A further object is an apparatus which is light in weight.

The invention also relates to an apparatus for the tension free, electrically insulating connection of two sections of the wire of an overhead line which can be assembled without causing deformation of the wire.

Another object of this invention is an apparatus which can be mounted on the wire before it is cut and which preferably is capable not only of being connected to the wire but also of being adjusted in the required position before the wire is cut.

Another object of the invention is an apparatus which can be assembled easily and quickly and can subsequently be mounted on the wire in an equally quick and simple manner.

The invention also relates to an apparatus which is inexpensive by virtue of its simple structure and ease of assembly.

Another object of the invention is an apparatus in which the capacity to insulate in the longitudinal direction of the wire has been improved so that faults on the line cannot occur even under unsuitable external conditions such as moisture, or deposition of dirt on the insulators, whereby regular servicing is unnecessary.

Another object of the invention is an aparatus in which the insulating bodies have improved protection against damage by arcing and improved capacity for suppression of an arc.

Another object of the invention is an apparatus constructed as a track insulator under which a vehicle can travel without the supply of current through the collector being interrupted.

The invention will now be described by way of example, with reference to the drawings, in which Figure 1 is a top plan view of a first exemplary embodiment constituting a phase insulator, Figure 2 is a side view of the first embodiment, Figure 3 is an enlarged section taken on the line Ill-Ill of Fig. 1, Figure 4 is an enlarged section taken on the line IV-IV of Fig. 1, Figure 5 is an enlarged section taken on the line V-V of Fig. 1, Figure 6 is an enlarged section taken on the line VI-VI of Fig. 1, Figure 7 is an enlarged section taken on the line VII-VII of Fig. 1, Figure 8 is an enlarged section taken on the line VIII-VIII of Fig. 1, Figure 9 is a top plan view of a second exemplary embodiment constructed as track insulator, Figure 10 is a side view of the second embodiment, Figure ii is a section taken on the line Xl-Xl of Fig. 9, Figure 12 is a top plan view of a third exemplary embodiment constructed as track insulator, and Figure 13 is an incomplete side view of a modified embodiment of an insulating rod and of the metal rod connected to one end thereof.

A phase insulator which is mounted on the contact or trolley wire of an overhead line for electrically driven railed vehicles and can be completely adjusted before a piece is cut out of the trolley wire to form two separated wire sections 10 and 11 and which joins the resulting ends of these wire sections 10 and 11 in a high tensile strength manner and so that they are electrically insulated from each other comprises, as shown in Figs. 1 and 2, two rod insulators indicated generally by the references 1 2 and 13, which are situated side by side parallel to each other at some distance apart and are identical in construction and not only electrically insulate the two sections of the trolley wire from each other but also transmit the tension exerted on the phase insulator by the wire sections.The distance between the longitudinal axes of the two rod insulators 1 2 and 1 3 in the exemplary embodiment given is very small, being not quite four times the external diameter of the insulators.

Since the insulating rods of a phase insulator must be earthed halfway along their length, each of the two rod insulators is composed of two similarly constructed insulating rods 14 comprising a glass fibre reinforced plastics rod 15' and a tube 1 5 of polytetrafluoroethylene (PTFE) surrounding the outside of the rod 15' at some distance from it. Each of the two ends of each rod 15' engages in a thick walled sleeve 1 6 made of metal, in particular a copper alloy but preferably an aluminium alloy, and is firmly united with this sleeve by mechanical pressing.The external diameter of the sleeve 1 6 is somewhat smaller than the external diameter of the tube 1 5 in order to ensure that a trolley brush moving over the phase insulator will not come into contact with the sleeve 16, in order to prevent wear of the sleeve. That end of the sleeve 1 6 which is remote from the rod 15' has a central threaded bore.

The sleeves 1 6 situated at those ends of the plastics rods 15' which face each other are joined by a connecting piece 1 7 (see Fig. 7) which is made of the same material as the sleeves 1 6 and the middle portion of which has the same external diameter as the sleeves.

The two end sections have threads and are screwed into the sleeves 1 6 which are to be joined together. The length of the middle portion of the connecting pieces 1 7 is chosen to ensure that the two rod insulators 1 2 and 1 3 will have exactly the same overall length.

The sleeves 1 6 situated at those ends of the insulating rods 12 and 1 3 which face away from each other bear with their end faces against one of the two crosspieces 18 which are common to both insulating rods. The identical cross-pieces 18, which are made of metal, for example a copper alloy or preferably an aluminium alloy to reduce their weight, have the form of an upright bar which is rectangular in cross-section.Each crosspiece 1 8 has two screws 1 9 passing through it at the same level and extending into the adjacent sleeves 1 6 to provide a tensionproof connection between the rod insulators 1 2 and 1 3 and the crosspieces 1 8. The distance of the screws 1 9 from the underside of the crosspieces 18 is chosen so that the underside of the rod insulators 1 2 and 1 3 is lower than the underside of the crosspiece. A groove 20 situated in the middle of each crosspiece 1 8 and open at the bottom partially receives the section of trolley wire 10 or 11, respectively.

A bolt 21 passing through the crosspiece 1 8 above the groove 20 and extending parallel to the sleeves 1 6 also penetrates a second crosspiece 22 (see Fig. 3) which is situated at some distance from the first crosspiece 18 and shifted in relation to the plastics rod 15' and, like the crosspiece 18, has the form of an upright bar which is rectangular in crosssection. The two second crosspieces 22 are also made of metal, for example a copper alloy, preferably an aluminium alloy. As shown in Fig. 5, each second crosspiece 22 has two symmetrically arranged circular grooves 23 which are open at the bottom and adapted to the external diameter of the sleeves 16 so that they grip them in the radial direction but leave them free at the bottom.

Since the second crosspieces 22 are not required to transmit the forces of traction, they are thinner than the first crosspieces 18. The trolley wire is partially enclosed in a recess 24 which is placed centrally at the lower edge of this crosspiece 22 and is open at the bottom.

The distance of the second crosspiece 22 from the first crosspiece 18 is determined by the length of a screw clamp 25 which forms a first clamp for the trolley wire and can be placed on the wire from above. This screw clamp comprises two jaws placed side by side which form an upper clamping channel for the bolt 21 and a lower clamping channel for the head of the trolley wire. The length of the screw clamp 25 and its clamping force are chosen so that the clamp is capable on its own of securely holding the section of wire 10 or 11.

Since the longitudinal axis of the rod insulators 12 and 1 3 is situated at a higher level that the longitudinal axis of th lower clamping channel of the screw clamp 25, in which the head of the trolley wire is held, the tension exerted on the phase insulator by the trolley wire produces a moment which tends to bend the end of the cut wire downwards. This moment is, however, compensated and therefore cannot cause the clamping channel which grips the head of the trolley wire to be shifted from its position parallel to the longitudinal axis of the rod insulators. This compensation is effected, firstly, by a bracing wire or cable 37 one end of which is attached to a strap 38 which is situated centrally on the second crosspiece 22 and projects above the top of this crosspiece.As can be seen from Fig. 2, the bracing cable 37 extends away from the strap 38 at an acute angle to a point on the supporting structure situated above the wire 10 or 11, where it.is attached.

Skids 26 arranged pairwise at both end sections of the phase insulator also prevent shifting of the position of the screw clamp 25.

The skids 26, which are made of an electrically higher conductive material and have a row of perforations 26' to reduce their weight are placed upright and lie against the external surfaces of the crosspieces 1 8 and 22, to which they are attached by screws, and they extend not only towards the middle of the rod insulators 1 2 and 1 3 but also in the opposite direction beyond the first crosspiece 18 to a second clamp 27 which grips the trolley wire section 10 or 11 at some distance from the first crosspiece. This second wire clamp 27 is situated between the ends of the two skids 26 which progressively approach each other from the first crosspiece 18, and the clamp is screwed to these ends of the skids.A downward displacement of the end of the screw clamp 25 adjacent to the second crosspiece 22 would tend to lift the second wire clamp 27, but this is prevented by the connection of the clamp 27 with the wire section.

This second wire clamp 27 can also be mounted on the trolley wire from above and also comprises two jaws placed side by side which between them clamp the head of the trolley wire, and they are held together by screws which also serve to connect the ends of the skids to the clamp.

As shown in Fig. 1, the middle section of the skids 26 extends from the first crosspiece 1 8 to and beyond the second crosspiece 22, and each skid is situated on the outside of one of the rod insulators 1 2 or 1 3 respectively, and extends parallel thereto at some distance from it. That end section of the skids 26 which adjoins the middle section near the middle of the rod insulators is bent at an angle away from the insulating rods 14 and carries at its free end an arc horn 28 which is attached by screws so that it can easily be adjusted and replaced.The underside of the skids 26, with the exception of the end section carrying the arc horn, is slightly below the underside of the crosspieces 1 8 and 22 and the underside of the sleeves 1 6 and of the rod insulators 1 2 and 1 3. A trolley brush sliding between the screw clamp 25 and the second wire clamp 27 would therefore move in contact with the underside of the skids 26 and of the trolley wire and would not come into contact with the underside of the tubes 1 5 until it reaches the transition from the middle section of the skids to their end section which carries the arc horn. Both transitions are smooth and free from jolts both in this and the opposite direction.

To increase their stability in the transverse direction, the skids may have an upper side piece as shown in Figs. 5 and 6. If the skids 26 are made of an aluminium alloy to save weight, it is advantageous, for the sake of obtaining sufficient abrasion resistance, to use a wire 26' of copper alloy to form the base of the skid along which the trolley brush slides, and fix the head of this wire in a clamping channel of the rail, as shown in Figs. 5 and 6.

That part of the skids 26 which is made of an aluminium alloy may be provided with an insulating layer 26" of polyfluoroethylene (PTFE).

The sleeves 1 6 which join the insulating rods 14 together and the connecting piece 1 7 of each rod insulator are held by two bridges 30 and a central bridge 31 between them, respectively. All these three bridges have substantially the same structure as the second crosspiece 22, i.e. they each have two grooves which are open at the bottom but grip the sleeve 1 6 and connecting piece 1 7 in the radial direction. Earth leads are attached to the two bridges 30, each by a cable shoe or the like. Two skids 32 similar in structure to the skids 26 bear against the external surfaces of the bridges 30 and 31.The function of these skids 32 is to carry a trolley brush smoothly from one insulating rod to the next without allowing it to come into contact with the bridges, the sleeves and the connecting pieces. The middle section of the skids 32, in which the skids are parallel to the insulating rods 1 4 and at some distance from the external side thereof, extends beyond the ends of the sleeves, as shown in Fig. 1. In the two end sections, the skids diverge so that their distance from the insulating rods 1 4 progressively increases. Arc horns 28 are replaceably attached to. the ends of the skids.

The two screws by which the skids 32 are attached to the end surfaces of the middle bridge 31 penetrate the adjacent connecting piece 1 7 and thereby fix it. Since the two skids are also screwed to the two bridges 30, these are also fixed.

Two supporting members 33 are screwed to the two sides of the bridge 31 facing the bridges 30 and another two to the side of the crosspieces 1 8 facing away from the crosspiece 22. These supporting members extend obliquely upwards and outwards, as shown for the bridge 31 in Fig. 8. For reasons of weight, they are in the form of upended perforated bars 33. The free ends of the supporting bars 33 serve for the attachment of suspension cables 34 by which the phase insulator is suspended to the supporting structure of the overhead line. Adjustment devices 36 arranged along the cables 34 enable the length of the cables to be exactly adjusted so that the phase insulator can also be adjusted.

In those sections of the insulating rods 14 in which a collector shoe does not slide along the underside of the tube 15 but along the skids 26 and 32, i.e. in the two end sections of the insulating rods 14 between the middle sections of the skids, annular grooves 39 are cut into the tubes 1 5 at intervals along the length of the tubes. These grooves 39 enable water or other liquids to drip more readily from the tubes and thereby prevent the formation of a continuous zone of soiled surface along the length of the rod and thus eliminate the possibility of surface leakage currents or flashover due to surface conduction. The insulating efficiency in the longitudinal direction is thus considerably improved by these annular grooves.

When such a phase insulator is mounted on a trolley wire which has not yet been severed, the insulator is placed on the trolley wire from above and the two clamping screws 25 followed by the two second wire clamps 27 are attached to the wire. The second wire clamps 27 would be capable of holding the cut wire sections on their own if for any reason the screw clamps 25 where no longer capable of holding the wire. Since the bridges 30 and 31 as well as the crosspieces 18 and 22 have a groove at the centre which is open at the bottom, into which the trolley wire can be fitted, assembly of the apparatus is not prevented by the presence of the continuous trolley wire.When the screw clamps 25 and the second wire clamps 27 have been tight- ened and the suspension cables 34 and bracing cables 37 have been placed in position and the apparatus has been adjusted by means of these cables, the trolley wire is cut at some distance from the second crosspiece 22. The end projecting from the second crosspiece 22 is then bent upwards slightly to lie sufficiently far above the surface along which the collector shoe slides.

The embodiment illustrated in Figs. 9 to 11 is a track insulator along which a collector shoe can travel in both directions. In the same way as the embodiment shown in Figs. 1 to 8, it can be mounted on the trolley wire of an overhead lead for electrically driven railed vehicles before the wire is cut and then insulates the two sections of the wire from each other when it has been assembled and the wire has been cut.

The construction of this exemplary embodiment is substantially similar to that constructed as phase insulator according to Figs.

1 to 8, and corresponding parts have therefore been indicated by the same reference numeral increased by 100, and where possible, to avoid repetition, reference has been made to the comments on the first embodiment.

Each of the two rod insulators 112 and 11 3 by which the trolley wire sections 110 and 111 are mechanically firmly attached to each other and electrically insulated from each other consists of a single glass fibre reinforced plastics rod and a tube of polytetrafluoroethylene (PTFE) concentrically surrounding the rod at some distance from it. This tube differs from the tube 1 5 in having annular grooves 1 39 arranged at intervals along the whole length of the tube. This arrangement considerably improves the insulating capacity in the longitudinal direction of the rod even under unfavourable external conditions and enables the length of the rod to be reduced to a minimum, thereby also reducing the weight of the track insulator.The construction is otherwise the same as that of the insulating rods 1 4 of the first embodiment. It is also similar to that of the first embodiment in that the two rod insulators 11 2 and 11 3 are each connected at their two ends to a thick walled sleeve 1 6 somewhat smaller in diameter which is made of a metal, for example a copper alloy but in particular an aluminium alloy, which, as in the first embodiment, is in turn connected to two crosspieces 11 8 and 1 22 similar in construction and arrangement to those of the first embodiment.The first wire clamp 1 25 which can be mounted on the trolley wire from above is arranged between the two crosspieces 118 and 1 22 of each pair of crosspieces. For the structure and method of fixing this clamp 125, see the corresponding part of the description relating to the first embodiment.A further similarity with the first embodiment is that the upended skids 1 26 in the form of perforated bars which carry the trolley brush smoothly over the track insulator lie against the external surfaces of the crosspieces 11 8 and 1 22 and are screwed to them and at one end of each pair of skids 26, the two skids carry a second wire clamp 1 27 which, situated at some distance before or behind the first clamp, respectively, grips the head of the trolley wire and has the same structure as the second wire clamp 27 of the embodiment according to Figs. 1 to 8.Lastly, each of the two second crosspieces 122 has a central strap 1 38 projecting upwards to which a bracing cable 1 37 is attached, in the same way as in the last mentioned embodiment.

The cables 1 37 have the same position and function as the bracing cables 37.

This embodiment differs from the first embodiment in that, as shown in particular in Fig. 9, only one of the two skids 126 which extend from one end of the track insulator towards the other ends in that half in which the two crosspieces supporting it are situated.

Furthermore, these two short skids do not have an end section which is angled off and diverges outwards, away from the rod insulator. Each of the two other skids extends beyond the crosspiece- 1 22 at the same angle as the end section situated between the second wire clamp 127 and the crosspiece 118 until it reaches the outer end of a transverse insulator 145. The following end section runs parallel to the rod insulators and extends beyond the middle of the insulators to overlap the short skid. The distance between the skids 1 26 in the region of overlap is a multiple of the distance between the short skid and the adjacent rod insulator. The distance between any arc that may occur and the rod insulators is therefore also relatively large.In order to reduce still further any risk of damage to the rod insulators by electric arcs, a vertical protective plate 149 of asbestos or the like is arranged on the outside of each of the short skids and attached to the crosspieces 118 and 1 22 to shield the rod insulators.

Like every short skid so also every long skid carries at its free end an arc horn 1 28 which is bent upwards and preferably detachably screwed to the skid. An extinction chamber generally indicated by the reference 140 is attached to this horn 1 28 and extends into the gap between said horn and the horn which is arranged on the same side of the track insulator and attached to the short skid of the other pair of skids. Fig. 9 shows that while the two rod insulators 11 2 and 11 3 extend horizontally, the two identical extinction chambers 140 form each a channel of rectangular cross-section which extends in the vertical direction, is open at the top and bottom and widens out from below upwards.

Extinction plates 142 are situated at intervals between the two parallel side walls 141 and disposed perpendicularly to these side walls.

As can be seen from Fig. 10, the channels formed by the plates 142 also widen out to their top end. The plates 142 and that wall 143 of the chamber which is furthest away from the arc horn 1 28 carrying the extinction chamber have each a central slot 144 which begins at the lower edge of the plate 142 or of the wall 1 43 and extends upwardly. These slots 144 vary in length, as shown in Fig. 11.

The length of the slots increases from that plate 142 which is closest to the horn 1 28 carrying the extinction chamber to that wall of the chamber which also has a slot.

In order that the arc horn of each of the shorter skids may have the same distance to the rod insulators as the associated horn with extinction chamber in spite of the considerable difference between the distance of the shorter skids 1 26 from the rod insulators and the distance of the overlapping end sections of the longer skids 1 26 from the rod insulators, the arc horns 1 28 of the shorter skids are formed by the end section of a rod which, as shown in Fig. 9, is in the form of a Ushaped piece 1 46 with parallel arms situated in a horizontal plane.One arm of this Ushaped rod lies in contact with the external surface of the shorter skid in the region of the two crosspieces 11 8 and 1 22 so that the free end of the rod points in the same direction as the free end of this skid to which the rod 146 is detachably connected. The arc horn 1 28 is formed in one piece with the other arm of the U-shaped rod and is bent upwards, away from the chamber 140.

The transverse insulator 145 made of a plastics material intersects the two rod insulators 112 and 11 3 at right-angles halfway along their length and extends beyond them.

Two subdivided crossover clamps 147 connect the transverse insulator 145 to the two rod insulators. The two end sections of the transverse insulator extending from the rod insulators to the skids 1 26 are substantially greater in diameter than the middle section and the rod insulators but their undersurface is still above the pathway defined by the undersurface of the two skids. The insulation capacity of the transverse insulator is increased by annular grooves formed in its end sections. The end faces of the transverse insulator 145 not only have the long skids 1 26 screwed to them, whereby the skids are stabilized, but they also have each a strap 148 to which a suspension cable 1 34 is attached.The transverse insulator therefore also serves as support for the rod insulators which can prevent them from sagging so that it is easier to adjust the skids 1 26 in such a manner that the undersurface of the rod insulators is only slightly higher than the undersurface of the skids.

In order to enable the position of the track insulators to be adjusted with precision in the assembled state, the suspension cables 1 34 acting on the two ends of the track insulator are attached in the same manner as in Figs. 1 to 8 to the support arms 1 33 which, like the arms 33 of the first embodiment, are attached pairwise to the two crosspieces 11 8 and extend upwards and outwards from these crosspieces transversely to the longitudinal direction of the track insulator so that they are arranged in the positions indicated in Fig. 7 for the first embodiment. The suspension cables 1 34 are attached to the free ends of these arms 133, and adjustment devices 1 35 are provided along the cables.

Shock absorbers may be provided, particularly if the apparatus is liable to be subjected to severe stresses, and this also applies to the embodiment according to Figs. 1 to 8.

Another exemplary embodiment illustrated in Fig. 1 2 is constructed, like the embodiment shown in Figs. 9 to 11, as track insulator over which the collector shoe of an electrically driven vehicle can travel without interruption of the current supply. In contrast to the embodiment of Figs. 9 to 11, however, the track insulator of Fig. 1 2 can only carry a collector shoe in one direction, namely from left to right as viewed in Fig. 1 2.

Since the construction of the embodiment illustrated in Fig. 1 2 is similar to that of the embodiment in Figs. 9 to 11 with the exception of the skids, as can be seen by comparing Fig. 9 with Fig. 12, similar parts are indicated below by the same reference numerals as that used in Figs. 9 to 11 increased by 100, and only the differences are described below.

Fig. 1 2 shows how the two crosspieces 218 and 222 provided at one end of the two rod insulators 212 and 213 are of equal length so that the two skids 226 attached to their end faces, which are mirror images of each other, resemble the shorter skids 1 26 of the embodiment illustrated in Fig. 9 to 11 in that they extend parallel to the rod insulators in the region adjacent to the crosspieces and in the following region in which they are situated on the outside of the rod insulators, and they end at some distance before the transverse insulator 245 which crosses the rod insulators at half their length.That end section of the two skids 226 which extends from the crosspiece 218 in the opposite direction approaches the trolley wire 211 at an acute angle as in the other examples and is connected to the wire 211 by means of a second wire clamp 227 which has the same construction as the second wire clamps of the other examples and therefore can also be placed on the top of the trolley wire 211 from above.

The second crosspiece 22 provided at the other end of the two rod insulators 212 and 213 is slightly longer than the nearby first crosspiece 218 because the two skids 226 attached to the end faces of these crosspieces resemble the long skids of the example illustrated in Figs. 9 to 11 in that they extend beyond the second crosspiece 222 to the transverse insulator 245 in the same direction as the end section between the crosspiece 218 and the second wire clamp 227, in other words at an acute angle to the trolley wire 210, and it is only shortly before reaching the transverse insulator 245 that they are bent off at an angle so that the end section attached to the end face of the transverse insulator 245 runs parallel to the rod insulators 212 and 21 3. This end section extends beyond the middle of the rod insulators and overlaps by a short length the short skid situated on the same side, in the same manner as the long skids in Figs. 9 to 11. It also carries, like the end sections of Figs. 9 to 11, an arc horn 228 which is bent upwards and backwards and to which is attached an extinction chamber 240 which is constructed and arranged in the same manner as the extinction chambers 140 of the first embodiment.

The two arc horns 228 of the short skids 226 are situated at the same distance from the longitudinal mid-plane of the track insulator as the two above mentioned extinction chambers 240, and these horns, like those described with reference to Figs. 9 to 11, are formed by the extension of a U-shaped arm 247 which is obtained by bending a rod and has the same form and arrangement as the arm 146. Furthermore, the rod insulators 212 and 21 3 resemble those of the second embodiment in that in the region in which the heat of arcs burning between the arc horn are liable to be damaging, they are shielded by protective plates 249 of asbestos or the like fixed to the outside of the short skids.

The construction of this track insulator is otherwise the same as that illustrated in Figs.

9 to 11 so that reference to the description of the said embodiment and of that illustrated in Figs. 1 to 8 may be had for further details.

The track insulator of Fig. 1 2 is therefore also light in weight and simple in construction.

Furthermore, it resembles the other embodiments in being easily and quickly mounted on a trolley wire which has not yet been severed without thereby entailing the risk of forming a kink in the wire. For this reason, the apparatus is assembled in the same manner as the embodiments of Figs. 1 to 11 by placing the whole apparatus on the trolley wire from above. The wire clamps for the trolley wires are then tightened and the position of the track insulator is finally adjusted by means of the suspension cables and bracing cables. All that remains then is to cut the trolley wire at two points between the two crosspieces 222 and for safety's sake also to bend the two ends of the wire slightly upwards.

If the glass-fibre reinforced plastics rods which forms the core of the rod insulator is enveloped by a tube of polytetrafluoroethylene, as in the embodiments described above, there is no difficulty in forming annular grooves in this tube because the grooves can be cut, for example by means of a multiple tool of a turning machine. If, however, the covering on the glass fibre reinforced rod is made of silicone rubber, a material which is eminently suitable for covering glass fibre reinforced plastics rods, such annular grooves cannot be cut into the covering tube, or at best only at intolerable expense. In that case, the mould in which the covering tube is produced must be provided with the necessary annular grooves, but this is an expensive process.

Fig. 13 shows a modified embodiment of a rod insulator 312 in which the tube 315 surrounding the glass fibre reinforced plastics rod 315' is made of silicone rubber. Such a rod insulator could be used in place of the insulating rods of the track insulators described above without requiring any constructional changes to these embodiments. As shown in Fig. 13, the tube 315 does not have annular grooves but one spiral groove 339. Such a spiral groove provides virtually the same improvement as annular grooves but the effort of incorporating such a spiral groove in the mould for the production of the tube 31 5 is considerably less than that required for the incorporation of annular grooves.

Claims (27)

1. Apparatus for the electrically insulating connection of two sections of the contact wire of an overhead line, comprising: two spaced parallel insulating rods of glass fibre reinforced plastics each attached at its ends to a respective metal rod; two first crosspieces on the wire and to which the two metal rods are connected in tensionproof manner at one or the other end, respectively, of the insulating rods; two first clamps for joining the wire to one or other of the two first crosspieces; two second crosspieces on the wire and arranged between and spaced from the two first crosspieces, one of the first clamps being connected to one of the second crosspieces while the other first clamp is connected to the other second crosspieces; and two pairs of skids, the two skids of one pair being attached to the one and the other side, respectively, of that pair of crosspieces comprising one of the first crosspieces and the nearby second crosspiece, the two skids of the other pair being attached to one and the other side, respectively, of the other pair of crosspieces comprising the two other crosspieces, and one of the two sections of each skid adjacent to that section which is attached to the crosspieces extending laterally to the adjacent insulating rod at a distance therefrom while the other of these two sections approaches the wire and, together with the corresponding end of the other skid of the pair, is attached at its end to the wire by a second clamp.

2. Apparatus according to claim 1 wherein each metal rod is coaxial with a respective insulating rod.

3. Apparatus according to claim 1 or claim 2 wherein the insulating rods are side by side.

4. Apparatus according to claim 3 wherein the first and second clamps are adapted to be placed on the wire from above.

5. Apparatus according to any preceding claim wherein a device for fixing a bracing wire is provided on each second crosspiece to compensate for the moment exerted on the pair of crosspieces both by the wire and by the insulating rods.

6. Apparatus according to any preceding claim wherein each first clamp is clamped to a bolt which extends from one to the other crosspiece of the associated pair of crosspieces parallel to the axis of the insulating rods and penetrates the two crosspieces.

7. Apparatus according to any preceding claim wherein each metal rod has a central threaded bore which is open at the end remote from the insulator, each bore receiving a screw which penetrates a bore of that crosspiece of the one or other pair of crosspieces which is further remote from the end of the insulator.

8. Apparatus according to any preceding claim wherein the skids are perforated bars.

9. Apparatus according to any preceding claim wherein the crosspieces and the skids, the latter with the exclusion of their marginal zone forming the contact surface for a current collector, are of a lightweight metal.

10. Apparatus according to any preceding claim wherein each insulating rod has a jacket of an electrically highly insulating material, which jacket has annular grooves or a spiral groove.

11. Apparatus according to claim 10 wherein the groove or grooves is or are provided only in that section in which the undersurface of the insulating rod is situated at a higher level than the contact path for a current collector defined by the skids which are disposed laterally.

12. Apparatus according to any preceding claim wherein the skids of one pair of overlap those of the other pair so that a current collector can travel over the insulating rods without interruption of current supply.

1 3. Apparatus according to any preceding claim wherein at least two of the four skids are attached to one or other end of a transverse insulator connected to the two insulating rods.

14. Apparatus according to claim 1 3 wherein the said at least two skids are attached by two clamps, the transverse insulator being of plastics material.

1 5. Apparatus according to claim 1 4 wherein attachment devices for suspension wires or cables are connected to the transverse insulator.

1 6. Apparatus according to any preceding claim wherein the end of each skid has an arc horn detachably attached to it.

1 7. Apparatus according to claim 1 6 wherein where skids overlap, the arc horn of that skid nearer the insulating rod being carried by a rod which is in alignment with the other skid, which rod forms one arm of a Ushaped member whose other arm is attached to the skid.

1 8. Apparatus according to claim 1 6 or 1 7 wherein those arc horns or skids where an interruption of current is liable to occur each carry an arc extinction chamber which is open from top to bottom.

1 9. Apparatus according to any preceding claim wherein the skids have a plastics coating covering them laterally and at the top.

20. Apparatus according to any preceding claim wherein each insulating rod comprises two coaxial insulating ods whose adjacent ends are connected by metal rods of smaller diameter which in turn are connected to bridges to which skids outside of the insulating rods are attached.

21. Apparatus according to claim 20 wherein the metal rods which join the adjacent ends of the insulating rods are in three sections, the two end sections af which are of the same shape as the metal rods which are connected to those ends of the insulating rods which are remote from each other, while the middle sector is a connecting piece engaging in a central threaded bore of the metal rods.

22. Apparatus according to claim 21 wherein the bridges are of the same structure as that crosspiece of the two pairs of crosspieces which is nearer to the end of the insulating rod.

23. Apparatus according to claim 22 wherein three bridges are provided at intervals in the longitudinal direction of the metal rods, the middle bridge holding the two connecting members and having one screw engaging in each connecting member in the radial direction.

24. Apparatus according to claim 23 wherein two outwardly directly supporting arms are attached to the middle bridge, each having a suspension wire attached to it.

25. Apparatus according to any of claims 21 to 24 wherein replaceable arc horns are attached to the ends of the skids carried by the bridges.

26. Apparatus according to any preceding claim wherein suspension wires act on laterally projecting supporting arms attached to the crosspieces.

27. Apparatus for the electrically insulating connection of two sections of the contact wire of an overhead line, the apparatus being constructed and arranged substantially as herein described and shown in the drawings.