Power transmission arrangement

Abstract

A power transmission arrangement comprises a first power transmission member connectable to a first main shaft of an engine. The arrangement also includes a second power transmission member connectable to a second main shaft of the engine and to a third power transmission member. A coupling assembly is provided which has a selectable coupling condition to couple the first power transmission member to the second power transmission member to allow power to be transmitted from the third power transmission member to the first main shaft of the engine via the first power transmission member. The coupling assembly has a decoupling condition to decouple the first power transmission member from the second power transmission member to allow power to be transmitted from the main shaft of the engine to the third power transmission member via the second power transmission member.

1 . A power transmission arrangement comprising a first power transmission member connectable to a first power assembly of a drive arrangement, a second power transmission member connectable to a second power assembly of a drive arrangement and to a third power transmission member, characterised by a coupling assembly having a selectable coupling condition to couple the first power transmission member to the second power transmission member to allow power to be transmitted from the third power transmission member to the first power assembly via the first power transmission member, and having a selectable decoupling condition to decouple the first power transmission member from the second power transmission member to allow power to be transmitted from the second power assembly to the third transmission member via the second transmission member.  
   
   
       2 . A power transmission arrangement according to  claim 1  wherein the coupling assembly is mounted on the first and second power transmission members.  
   
   
       3 . A power transmission arrangement according to  claim 1  wherein the coupling assembly comprises a fluid operated clutch.  
   
   
       4 . A power transmission arrangement according to  claim 1  wherein the coupling assembly comprises a main body, having first and second parts movable relative to each other.  
   
   
       5 . A power transmission arrangement according to  claim 4  wherein the second power transmission member comprises a connection member to drivingly connect the third power transmission member thereto.  
   
   
       6 . A power transmission arrangement according to  claim 5  wherein the connection member comprises a gear to drivingly connect the third power transmission member to the second transmission member.  
   
   
       7 . A power transmission arrangement according to  claim 5  or  6  wherein the second power transmission member extends through the main body to said connection member.  
   
   
       8 . A power transmission arrangement according to  claim 7  wherein the first part comprises a first fluid chamber, and the second part comprises a second fluid chamber, the first and second parts being in fluid communication with each other.  
   
   
       9 . A power transmission arrangement according to  claim 8  wherein each of the first and second fluid chambers is of an annular configuration.  
   
   
       10 . A power transmission arrangement according to  claim 9  wherein each of the first and second fluid chambers is of a toroidal configuration.  
   
   
       11 . A power transmission arrangement according to  claim 9  wherein the main body has a configuration of a torus defining a space to receive at least one of said first and second power transmission members.  
   
   
       12 . A power transmission arrangement according to  claim 11  wherein the space receives both of said first and second power transmission members and the second power transmission member extends wholly through the aforesaid space.  
   
   
       13 . A power transmission arrangement according to  claim 8  wherein each of the chambers includes a plurality of radially extending vanes.  
   
   
       14 . A power transmission arrangement according to  claim 4  wherein the main body includes drain means to allow fluid in the main body to drain there from.  
   
   
       15 . A power transmission arrangement according to  claim 14  wherein the drain means comprises a drain aperture or a plurality of drain apertures defined in the main body, the, or each, drain aperture being defined in a region between the first and second chambers.  
   
   
       16 . A power transmission arrangement according to  claim 8  wherein the coupling assembly comprises an enclosure in which the main body is arranged, and fluid from the main body can drain into the enclosure.  
   
   
       17 . A power transmission arrangement according to any of  claims 8  to  16  wherein the coupling assembly comprises a fluid supply system to supply fluid to the main body.  
   
   
       18 . A power transmission arrangement according to  claim 17  wherein the fluid supply system is arranged to supply fluid to the main body via the central member extending into, or through, said central space.  
   
   
       19 . A power transmission arrangement according to  claim 17  wherein the fluid supply system is arranged to supply to the main body externally of the central space.  
   
   
       20 . A power transmission arrangement according to  claim 19  wherein the fluid supply is supplied through one or more fluid supply holes in the main body.  
   
   
       21 . A power transmission arrangement according to  claim 4  wherein the first part is fixedly mounted on the first power transmission member, and the second part is fixedly mounted on the second power transmission member.  
   
   
       22 . A power transmission arrangement according to  claim 1  wherein the first and second power transmission members comprise shafts, arranged coaxially relative to each other.  
   
   
       23 . A power transmission arrangement according to  claim 22  wherein the second power transmission member is arranged within the first power transmission member.  
   
   
       24 . A power transmission arrangement according to  claim 1  wherein the coupling assembly is offset from the first and second power transmission member and is connected to the first and second power transmission members by at least one ancillary gear arrangement.  
   
   
       25 . A drive arrangement comprising first and second power assemblies and a power transmission arrangement according to any preceding claim, wherein the first power assembly is connected to the first power transmission member, and the second power assembly is connected to the second power transmission member.  
   
   
       26 . A drive arrangement according to  claim 25  wherein the first power assembly comprises a first compressor, a first turbine and a first torque transmitter to transmit torque to the first compressor form the first turbine, and the second power assembly comprises a second compressor, a second turbine and a second torque transmitter to transmit torque from the second turbine to the second compressor, the first power transmission member being connected to the first torque transmitter and the second power transmission member being connected to the second torque transmitter.  
   
   
       27 . A drive arrangement according to  claim 25  further including a starter for starting the drive arrangement, wherein the power transmission arrangement can couple together the first and second power transmission members during starting, whereby the starter can turn both of the first and second torque transmitters during the aforesaid starting of the drive arrangement, and can decouple the first and second torque transmitters after the aforesaid starting to permit independent operation of the first and second power assemblies.  
   
   
       28 . A drive arrangement according to  claim 27  wherein the starter is connected to the third power transmission member to drive the first and second torque transmitters during the aforesaid starting.  
   
   
       29 . A drive arrangement according to  claim 25  including power receiving means connected to the second torque transmitter, and the second torque transmitter drives the power receiving means after decoupling of the first and second torque transmitters from each other.  
   
   
       30 . A gas turbine engine incorporating a drive arrangement according to  claim 25  wherein the first compressor comprises a high pressure compressor, the first turbine comprises a high pressure turbine, and the first torque transmitter comprises a first main shaft interconnecting the high pressure compressor and turbine.  
   
   
       31 . A gas turbine engine incorporating a drive arrangement according to  claim 25  wherein the second compressor comprises an intermediate pressure compressor, the second turbine comprises an intermediate pressure turbine, and the second torque transmitter comprises a second main shaft interconnecting the intermediate pressure compressor and turbine.  
   
   
       32 . A coupling assembly comprising a main body having a first part selectively coupled by fluid to a second part, the first part being mountable on a first power transmission member and the second part being mountable on a second power transmission member, the main body defining a space to receive at least one of the power transmission members, and the coupling assembly further comprising fluid supply means for supplying fluid to the main body via a region of the main body outside the aforesaid space.  
   
   
       33 . A coupling assembly according to  claim 32  wherein the fluid is a hydraulic fluid, the first part comprises a first fluid chamber and the second part comprises a second fluid chamber.  
   
   
       34 . A coupling assembly according to  claim 33  wherein each of the first and second fluid chambers is of an annular configuration.  
   
   
       35 . A coupling assembly according to  claim 34  wherein each of the first and second fluid chambers is of a toriodal configuration, each of the aforesaid toroids being defined by a semi-circle.  
   
   
       36 . A coupling assembly according to  claim 32  wherein the main body has a configuration of a torus defining said space, the space being a central space of the torus.  
   
   
       37 . A coupling assembly according to  claim 36  wherein the space can receive the second power transmission member, which can extend wholly through the space.  
   
   
       38 . A coupling assembly according to  claim 32  wherein each of the fluid chambers includes a plurality of radially extending vanes.  
   
   
       39 . A coupling assembly according to  claim 32  wherein the main body includes drain means to allow fluid in the main body to drain therefrom.  
   
   
       40 . A coupling assembly according to  claim 39  wherein the drain means comprises a drain aperture or a plurality of drain apertures defined in the main body and the, or each, drain aperture is defined in a region between the first and second chambers.  
   
   
       41 . A coupling assembly according to  claim 39  wherein the coupling assembly includes an enclosure in which the main body is arranged, and fluid from the main body can drain into the enclosure.