Electrical connector arrangement

An electrical connector arrangement comprises a metal mounting bracket for securing the arrangement to a structure; an electrically insulating mounting block abutting the mounting bracket; a clamp to secure an electrical cable to the mounting block, the electrical cable comprising a plurality of electrical conductors; and a plurality of spaced-apart terminals to accommodate the respective electrical conductors.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is based upon, and claims the benefit of priority from UK Patent Application No. GB 1703520.5, filed on Mar. 6, 2017, the entire contents of which are hereby incorporated by reference.

BACKGROUND OF THE INVENTION

Field of the Invention

The present disclosure concerns electrical connectors, and particularly electrical connectors suitable for use in high temperature environments.

Description of the Related Art

A modern gas turbine engine requires a large number of thermocouples to measure temperatures in various locations, for the purposes of engine monitoring and control. Thermocouples are electrical devices, and therefore need to be removably connected to the engine control harnesses; this is achieved by the use of connector blocks (otherwise known as disconnect terminals). This allows individual thermocouples to be removed or replaced as required. The electrical conductors of thermocouples and harnesses are commonly terminated with ring tags or similar end fittings.

The positioning of known connector blocks is limited by their temperature capability, so that when high temperatures are to be measured it is necessary to locate the connector block some distance from the measurement position. This may be detrimental to the measurement quality and also complicates removal and replacement of the thermocouples, since longer flying leads are needed, which must be routed and secured between the measurement position and the connector block.

It would be desirable to have a connector block capable of operating at high temperature, so that it can be located near to the measurement position. It would be desirable to have a connector block that facilitates easy removal and replacement of thermocouples.

BRIEF SUMMARY OF THE INVENTION

Therefore, according to a first aspect there is provided an electrical connector block comprising: a metal mounting bracket for securing the arrangement to a structure; an electrically insulating mounting block abutting the mounting bracket; a clamp to secure an electrical cable to the mounting block, the electrical cable comprising a plurality of electrical conductors; a plurality of spaced-apart terminals to accommodate the respective electrical conductors.

Each electrical conductor may comprise an end fitting which is mechanically secured to a respective terminal using a fastener. The end fitting may be a ring tag.

Each terminal may comprise a conductive sleeve. The turret may extend through a thickness of the mounting block.

The length of the sleeve may be greater than the thickness of the mounting block.

This ensures good mechanical contact, and therefore a sound electrical contact, between the electrical conductor and the conductive sleeve.

The respective sleeves of the plurality of terminals may protrude different distances from the mounting block in the thickness direction so that the terminals are offset.

This allows better access to the nuts and bolts and the possibility to tailor the pot seal so that the respective electrical conductors emerge from it in the correct positions for the offset terminals.

The fastener may be a bolt.

Each sleeve may be made from the same material as its corresponding electrical conductor.

This ensures a consistent and matching material as far as possible through the electrical connector block so that the electrical continuity and signal integrity are optimised.

The electrical cable may be a thermocouple.

The clamp may be attached to the mounting block by clamp bolts.

The mounting bracket may engage with the clamp bolts to provide electrical bonding.

The terminals may configured to prevent incorrect connection of the electrical conductors.

This reduces the risk of errors and misconnections during assembly or reassembly.

The mounting bracket may be embedded within the mounting block.

More than one clamp and more than one corresponding plurality of terminals may be provided on the mounting block.

Clamps and terminals may be provided on opposite sides of the mounting block.

The mounting block may profiled to provide recesses to accommodate the electrical cables or pot seals.

This provides more positive location for the components being mounted on the mounting block, and also provides greater protection for them by partially embedding them into the mounting block.

The mounting block may be profiled to provide turrets of differing heights to support the terminals.

This allows better access to the nuts and bolts and the possibility to tailor the pot seal so that the respective electrical conductors emerge from it in the correct positions for the offset terminals.

The mounting bracket may be embedded within the mounting block.

This may allow a more compact assembly, and may reduce weight by reducing the number of fasteners.

More than one clamp and more than one corresponding plurality of terminals may be provided on the mounting block. Clamps and terminals may be provided on opposite sides of the mounting block.

The clamps may be separately attached to the mounting block so they can be loosened and tightened independently.

The skilled person will appreciate that except where mutually exclusive, a feature described in relation to any embodiment may be applied mutatis mutandis to any other embodiment. Furthermore, any feature described herein may be combined with any other feature described herein, unless they are mutually exclusive.

DETAILED DESCRIPTION OF THE INVENTION

With reference toFIG. 1, a gas turbine engine is generally indicated at10, having a principal and rotational axis11. The engine10comprises, in axial flow series, an air intake12, a propulsive fan13, an intermediate pressure compressor14, a high-pressure compressor15, combustion equipment16, a high-pressure turbine17, an intermediate pressure turbine18, a low-pressure turbine19and an exhaust nozzle20. A nacelle21generally surrounds the engine10and defines both the intake12and the exhaust nozzle20.

The compressed air exhausted from the high-pressure compressor15is directed into the combustion equipment16where it is mixed with fuel and the mixture combusted. The resultant hot combustion products then expand through, and thereby drive the high, intermediate and low-pressure turbines17,18,19before being exhausted through the nozzle20to provide additional propulsive thrust. The high17, intermediate18and low19pressure turbines drive respectively the high pressure compressor15, intermediate pressure compressor14and fan13, each by suitable interconnecting shaft.

During the operation of the gas turbine engine, temperatures are measured at various positions in the engine for the purposes of engine monitoring and control. The thermocouples are removably connected to the engine control harnesses via connector blocks, one of which is shown schematically at25.

FIG. 2shows a known electrical connector block25. The block is formed as a single monolithic piece30, which is secured to the engine structure via bolts32. Thermocouple34is terminated by a pot seal36, which is clamped to the monolithic piece30by a clamp38. The electrical conductors of the thermocouple are secured to respective terminals40.

On the other side of the monolithic piece30, but not visible inFIG. 2, part of the engine control harness42is secured to the monolithic piece30, and the electrical conductors39of the thermocouple34are electrically connected to respective electrical conductors of the engine control harness42via the terminals40.

FIG. 3shows schematic orthogonal views of an embodiment of an electrical connector block shown generally at125.

The electrical connector block125comprises a bracket150which may be secured to engine structure via bolts (not shown), and an electrically insulating mounting block152secured to the bracket150. In this embodiment, the bracket is made of metal, which gives it a high temperature capability; it can therefore be mounted directly to a hot casing of the gas turbine engine. The metal bracket also provides electrical bonding between the electrical connector block and the gas turbine engine casing, ensuring electromagnetic compatibility. For this purpose, the mounting bracket may in some embodiments be extended so that an electrical bonding connection can be made with the clamp or its fasteners.

The electrically insulating mounting block is made of ceramic; as well as electrical insulation this provides thermal insulation, minimising the conduction of heat from the bracket150and the engine structure. The provision of a separate bracket allows a single, standard design of mounting block to be used with a number of different brackets, each bracket being configured to suit the particular mounting requirements of a given location or engine.

A thermocouple154is terminated by a pot seal156, which is secured to the mounting block152by a clamp157. The electrical conductors158of the thermocouple terminate in ring tags159. The ring tags159are secured to respective terminals160by bolts162, which extend through a thickness of the mounting block152. At their opposite end, the bolts162engage with respective ring tags164, which terminate electrical conductors (not shown) of an engine control harness (not shown). The terminals160provide an electrical connection between the electrical conductors158of the thermocouple and the respective electrical conductors of the engine control harness. In this way, the electrical signal from the thermocouple may be transferred to engine monitoring and control systems.

Because an electrical connector block as shown inFIG. 3can be located on the engine close to the measurement position, separate electrical connector blocks can be used for each temperature measurement that is required.

Because individual connector blocks are relatively small and compact they are easy to accommodate in whatever position is convenient. These arrangements reduce or eliminate the need for large mounting assemblies.

FIG. 4is a cross-sectional view on the line A-A ofFIG. 3, showing more detail of the terminals160.

Each terminal160a,160bcomprises a bolt162a,162bwhich extends through the electrically insulating mounting block152and is secured by a nut166a,166b. Each bolt162a,162band its respective nut166a,166bsecures together a ring tag159a,159bterminating an electrical conductor of the thermocouple, an electrically conductive sleeve168a,168band a ring tag164a,164bterminating an electrical conductor of the engine control harness. The electrically conductive sleeves168a,168bare coaxial with the bolts162a,162b.

As is well known, the two electrical conductors of a thermocouple are made from different metals. In this embodiment, each electrically conductive sleeve168a,168bis made from the same metal as the respective ring tag159a,159b, which in turn is made from the same metal as its respective electrical conductor. In this way, by ensuring a consistent and matching material as far as possible through the electrical connector block, the electrical continuity and signal integrity are optimised. For example, a K-type thermocouple has one chromel conductor and one alumel conductor. The ring tag and conductive sleeve for the chromel conductor would therefore be made from chromel, and the ring tag and conductive sleeve for the alumel conductor would be made from alumel.

It is envisaged that the bolts162and nuts166would be standard aerospace items, as used elsewhere on the engine. Such fasteners are readily available as spares and will therefore be more economical when replacement is required. Also, because they are made to aerospace standards their durability will be more suitable for the conditions experienced in gas turbine engines. Maintenance and repair are simplified because these standard fasteners can simply be removed and replaced without disturbing the rest of the electrical connector block.

FIG. 5is an enlarged view of the region indicated as B inFIG. 4. The conductive sleeve168bis longer than the thickness of the mounting block152, so that there is a clearance170between the mounting block152and the ring tag159bwhen the bolt162band nut166bare tightened. There is a similar clearance (not labelled) on the other side of the mounting block152, between the mounting block and the ring tag164b. The lengthening of the conductive sleeve168bto provide these clearances ensures good mechanical contact, and therefore a sound electrical contact, between the ring tags159b,164band the conductive sleeve168b.

Referring again toFIG. 4, it can be seen that the conductive sleeve168ais longer than the conductive sleeve168b, and the bolt162ais longer than the bolt162b. The effect of this is that the ring tag159asits further away from the mounting block152than does the ring tag159b, staggering the connectors. This offers a number of advantages, including better access to the nuts and bolts and the possibility to tailor the pot seal156so that the respective electrical conductors emerge from it in the correct positions for the staggered connectors. Such an arrangement would help to prevent incorrect connection. It would be possible, alternatively or additionally, to make the ring tags or bolts of different shapes or sizes, so that each ring tag can only be connected to the correct terminal.

FIG. 6shows schematic orthogonal views of a second embodiment of an electrical connector block. As described above, a thermocouple154is terminated by a pot seal156, which is secured to a mounting block152by a clamp157. One electrical conductor158(only one is visible inFIG. 6) of the thermocouple is terminated by a ring tag159. The ring tag159is secured to a terminal160by a bolt162, which extends through a thickness of the mounting block152.

At its opposite end, the bolt162engages with a ring tag164, which terminates an electrical conductor of an engine control harness172. The engine control harness is terminated by a pot seal174, which is secured to the mounting block152by a clamp176. Because the clamps157,176are offset or staggered, one side of the termination can be disassembled while leaving the other side undisturbed and still restrained. This simplifies disassembly and reassembly and reduces the risk of unintended damage to connectors.

FIG. 7shows comparative views of two alternative embodiments of an electrical connector block.

The right-hand embodiment is similar to that shown inFIGS. 3 to 6, in which the mounting block152has a flat rectangular shape of uniform thickness. As described above, a pot seal156is secured to the surface of the mounting block152by a clamp157. On the opposite side of the mounting block152, the electrical conductors of the engine control harness are not, in this embodiment, terminated by a pot seal, but are simply flexible cables180terminated in ring tags (not shown). The flexible cables180are secured to the surface of the mounting block152by a saddle clamp182of flatter design.

The left-hand embodiment shown inFIG. 7, by contrast, has a profiled mounting block252with a larger recess284on one side to accommodate a pot seal256, and two smaller recesses286on its other side to accommodate flexible cables280. As in the right-hand embodiment, the pot seal and flexible cables are secured to the mounting block252by clamps, respectively257and282. However, in the case of the left-hand embodiment, the pot seal256and flexible cables282are now located in the respective recesses284,286. This provides greater protection for the pot seal256and flexible cables282, and also helps to ensure their correct location on the mounting block252when fitting or refitting.

As shown inFIG. 7, the profiled mounting block252can be made thicker than the flat mounting block, yet the overall thickness of the electrical connector block including the electrical conductors is no greater. The thicker mounting block252does however offer advantages of greater protection and easier location, as mentioned above. Alternatively, the profiling of the mounting block with recesses284,286may be used to reduce the overall thickness of the assembly.

FIG. 8shows a schematic view of a third embodiment of an electrical connector block, similar to the left-hand embodiment ofFIG. 7. In this embodiment, a layer290of padding material (of suitable temperature capability) is provided between the pot seal256and the recess284, so that the pot seal256is clamped between the clamp257and the padding material290. The padding material290may provide cushioning, damping or thermal insulation or a combination of these.

FIG. 9shows schematic orthogonal views of a fourth embodiment of an electrical connector block. A ceramic mounting block352is attached to a bracket350, which in turn is attachable to engine structure (not shown). In this embodiment, the mounting block is configured to accommodate two thermocouples354a,354b, which (as described above) are terminated by pot seals356a,356band secured to the mounting block352by clamps357a,357b. As in the other embodiments, the electrical conductors of the thermocouples are secured to respective terminals360.

It will be seen from the right-hand view inFIG. 9that the mounting block352is profiled to provide taller392and shorter394turrets to support the terminals390. This provides additional support for the offset or staggered terminals described in a previous embodiment, and may also help to ensure correct connection of the electrical conductors.

Except where mutually exclusive, any of the features may be employed separately or in combination with any other features and the disclosure extends to and includes all combinations and sub-combinations of one or more features described herein.

It will also be understood that the invention is not limited to the embodiments described above and various modifications and improvements can be made without departing from the concepts described herein.

In particular, the mounting bracket may in some embodiments be embedded within the mounting block, rather than being a discrete component. Although there is some loos of modularity, this may allow a more compact arrangement and may also allow a reduction in the number of bolts or other fasteners, which may reduce the weight of the electrical connector block.

The pot seal clamps may be P-clamps or of any other suitable design, rather than the saddle clamps in the described embodiments.

As an alternative to the embodiment shown inFIG. 9, a single mounting bracket may be configured to accommodate more than one mounting block and each mounting block terminates a single thermocouple.