Telescopic tubular power transmitting unit

A power transmitting unit, comprising a tubular inner member having a generally cylindrical axial outer section and having an externally splined axial inner section disposed axially inward of said cylindrical section, a central member having an internal spline and an external spline, said splines extending substantially the full length of said central member and said internal spline engaged with the splined section of the inner member, and outer member having a generally cylindrical axial outer section and an internally splined axial inner section disposed axially inward of said last named cylindrical section and engaged with the external spline of the central member, said inner and outer members being mounted for telescopic sliding movement with respect to the central member between retracted and extended positions, first universal coupling means connected to the outer end of the inner member, second universal coupling means secured to the outer end of the outer member, first guide ring means disposed within a circumferential groove in the internal spline of the central member and disposed to ride against the cylindrical section of the inner member as said inner member is moved axially with respect to the central member, said first guide ring means being disposed adjacent an end of said central member, said first guide ring means disposed to be engaged by the end of the splined section of said inner member to limit outward telescopic movement of said inner member in said extended position whereat the splined section of the inner member is disposed wholly within the central member, and second guide ring means located adjacent the opposite end of the central member and disposed within a circumferential groove in the external spline of said central member, said second guide ring means disposed to ride against the cylindrical section of the outer member on axial movement of said outer member relative to said central member, engagement of the end of said splined section of the outer member with said second guide ring means serving as a stop to limit outward telescopic movement of said outer member relative to said central member, a tubular shield disposed radially outward of said outer member, said inner and outer members being movable axially relative to said shield, said shield having a length substantially equal to the distance between said first and second universal coupling means when the inner and outer members are in the retracted position, and said unit having means for maintaining the shield in a spaced radially outward location with respect to the central member on extension and retraction of said inner and outer members.