User manual

Barrett Technology, Inc.
BA4-310 System User Manual Version 1.1
25
4 Overview of Cable Transmissions
4.1 Terminology
Before this manual discusses the cabled transmissions in the BarrettArm or BarrettWrist, it will
be helpful to define some general terms common to cabled systems.
Cable
– a “wire rope” typically made from very fine strands of stainless steel. The composite
tensile strength and stiffness is very high in a stranded cable yet it maintains flexibility in
bending.
Termination
– also referred to as a “lug”, it is a brass cylinder, which serves as an anchoring
point swaged or crimped onto the end of a cable. This term is also sometimes used to describe
the physical feature in a transmission circuit, which retains a lug.
Pinion
– the smaller diameter, higher-speed cylinder in a pair of cabled transmission elements.
A pinion usually has guide grooves for cables cut into its surface.
Pulley
– the larger diameter, slower-speed cylinder in a pair of cabled transmission elements.
A pulley’s surface is typically smooth and has no cable guide grooves.
Cable circuit
– the cables and cable paths through a transmission from motor to output
Stages
– as with gear trains, cable circuits can be comprised of several transmission stages,
each contributing its part to the final transmission ratio.
Open wrap
– when spanning the distance between two parallel transmission elements (pinions
or pulleys) the drive cable does not cross the plane, which contains the axes of both elements.
This results in both elements rotating in the same direction when cabled.
Cross wrap
– when spanning the distance between two parallel transmission elements (pinions
or pulleys) the drive cable crosses the plane, which contains the axes of both elements. This
results in the elements rotating in opposite directions when cabled.
Pinion
Pulley
P ulle
y
Pinion
Cross Wrap Open Wrap