Universal Joints and Driveshafts H.Chr.Seherr-Thoss · F ... - Index of

24 1 Universal Jointed Driveshafts for Transmitting Rotational Movements
a
c
Fig. 1.26a–d. Bernard Stuber’s offset steering 1933 (US patent 1975758). a, b The offset (by c)
of the generating centres O 1 and O 2 means that the tracks R and r intersect even in the non-articulated
joint and position the balls automatically in the plane of symmetry. c The generating
centres of the tracks O 1 and O 2 lie on the joint axis O 1OO 2 when the joint is not at an angle.
When it articulates through b, O 1 is lifted on an arc of radius c about O towards O¢ 1.Point O 2
does not move. Hence line O¢ 1O 2 forms the semi-articulation angle b/2 with the axis of the output
member 2. The balls are thus steered into the plane of symmetry p which, as shown in a–d,
is the condition for the uniform transmission of rotation by intersecting shafts. d The relationship
of c–d is based on Euclid’s subtended angle theorem. *
Intersecting Angles c = 18° to 40°
These angles still steer the balls properly but need auxiliary elements (HE) to guide
them. For VL-plunging joints, the tracks intersect at 32° (SR). They need a ball cage
so that when the joint articulates, the balls do not fall out of the tracks. On the Devos
joint with straight tracks (Fig. 1.30) and intersecting angles of about 24°, a pin guides
the rotatable and axially free outer balls of its three-ball unit into the plane of symmetry
p.
The ball tracks of RF fixed joints intersect at 18° to 20° due to the track offset
(RO). The opening angle d of the tracks must be larger than twice the friction
* “The subtended angle is half as big as the centre angle over the same arec.” (Fig. 1.26d).
Euclid/Clemens Thaer, Die Elemente (The Elements), Book 3, Section 21, Darmstadt:
Wissenschaftl. Buchges. 1980.
b
d