892-0000010B OM
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3.3.3 Gearbox control
The gearbox control consists of yoke body 3 (Figure 3.3.1) and gearbox control cover
15, which are installed on the upper surface of gearbox housing 29 and fastened to it with
bolts.
Yoke housing 3 consists of yoke of 1st speed and reverse 20 (Figure 3.3.2), yoke of
3rd and 6th speeds 21, yoke of 4th and 5th speeds 12 and arm of range gear unit 13, the
slides of which are installed in the groove of body 1 and have the ability to move along the
groove. On the upper surfaces of the slides there are transverse holes for spring-loaded
retainer balls 10, which ensure fixation of the yoke slides and the gear unit slide in the given
positions, and also prevent the speeds from disengagement automatically under load.
Speed shifting is carried out by yokes 12, 20 and 21, the mouths of which enter the
annular grooves of the corresponding gears. Shifting between the passes of the range gear
unit is carried out by arm 13, which is connected to shaft 11 (Figure 3.3.1), on which yoke
fork 9 is fixed. Yoke 9 controls drive gear of 1st pass of range gear unit 24.
The yoke slides have grooves, and the arm of the range gear unit has a “pocket” for
gear lever 4 (Figure 3.3.2) installed on shaft 2 of cover 22 of gearbox control. Since gear
shifting is preceded by the selection of the appropriate range of the gearbox, the shape of
the “pocket” is made in such a way that it provides unimpeded exit of gear lever 4 from it
into the grooves of the yoke slides for subsequent speed selection.
The slides of the yokes and the range gear unit are separated from each other by
three locking bars 11. Bars 11 are rigidly mounted in housing 1 and prevent the simultaneous
movement of several slides by gear lever 4. When the speed is engaged, lock bars 11 “lock”
gear lever 4 in the groove of the yoke slide of the speed engaged.
Gearbox control cover 15 (Figure 3.3.1) consists of cover 22 (Figure 3.3.2), in the
bore of pipe 5 of which cantilever support 7 is installed. Support 7 has the ability to swing in
the longitudinal plane, and its axial movement is blocked by stopper 6, which enters the slot
of the support pipe. Inside support 7 there is shaft 2, on which gear lever 4 is fastened with
a key and a clamp. Support 7 and shaft 2 are interconnected by means of splines, which
allow shaft 2 and gear lever 4 to swing in the longitudinal plane along with support 7. When
swinging, gear lever 4 directly affects the slides in yoke body 1, causing them to move and,
accordingly, turning on or off the selected gear or range in the gearbox. Shaft 2 has the
ability to move axially along the splines of the tube of support 7, which is necessary for
selection of the required slide in fork body 1.
To exclude excessive swing amplitudes of gear lever 8 (Figure 3.3.1), as well as for
a clear direction of its movement, there is limiting plate 14, which is attached to cover 15 by
means of bolts.
The gearbox is controlled by the operator from the workplace by acting on gearbox
control lever 9 (Figure 3.3.2). In this case, the swing of gearbox control lever 9 in the trans-
verse plane through arm 8 causes axial movement of shaft 2 and the selection of the desired
slide in yoke body 1 (selection of gear or range). The swing movement of gearbox control
lever 9 in the longitudinal plane is carried out simultaneously with support 7, and causes a
gear or a range of the gearbox to be engaged.
The design of gearbox control cover 15 (Figure 3.3.1) provides a clear choice of the
required gear due to a clear hitting of each of the slides of yoke body 3 by gear lever 8. For
this reason, there is a flat on gear shaft 2 (Figure 3.3.2), in which there is spring-loaded ball
3.
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