Patent ID: 7591089

Claim:
A boom assembly comprising: a primary boom member having one end attachable to a vehicle; a secondary boom member pivotally attached to the free end of the primary boom member for rotation of the secondary boom member about a first axis relative to the primary boom member, the secondary boom member including a secondary boom attachment portion and a main body portion; and a swivel mechanism configured to enable the secondary boom member to be rotated relative to the primary boom member about a second axis of rotation independently to rotation of the secondary boom member relative to the primary boom member about the first axis of rotation, the swivel mechanism including: a rotary actuator that has a first fixed portion attached to the secondary boom attachment portion and a second portion rotatable relative to the fixed portion in response to the application of hydraulic fluid pressure thereto, the second portion being attached to the main body portion for rotating the main body portion about the second axis; a bearing plate attached to the secondary boom attachment portion and a rotary adapter plate attached to the main body portion, the bearing and adapter plates facing and being spaced from each other by the rotary actuator; and a bearing housing mounted to the second portion of the rotary actuator so that the bearing housing rotates together with the main body portion about the second axis, the bearing housing being dished to form an annular recess that faces the bearing plate of the secondary boom attachment portion, wherein a dividing wall upstands from the bearing plate towards the bearing housing to divide the annular recess into radially inner and radially outer bearing compartments.