Assembly Drawings 335
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d:\N-Design\Des18-4.pm5
The gland 2 is fastened to the bracket 1 by means of the studs 7 and nuts (not shown). The
bush 3 is fitted into the bracket and positioned by means of a set screw (not shown). The shaft 4
is introduced into the above assembly and gear wheel 6 is mounted on the left side of the shaft and
V-pulley 5 is mounted on the right side by means of woodruff keys (not shown). The gear wheel
and V-pulley are fixed in position by means of two nuts (nut shown). The assembly permits free
rotation of the shaft in the bracket, and the gland and the bush serve as bearings for the shaft.
Exercise
Figure 18.50 shows the details of a V-belt drive. Assemble the parts and draw the following views,
to a suitable scale:
(i) Sectional view from the front and
(ii) View from the right (not showing the V-pulley).
18.5.13 Screw Jack
Screw jacks are used for raising heavy loads through very small heights. Figure 18.51 shows the
details of one type of screw jack. In this, the screw 3 works in the nut 2 which is press fitted into
the main body 1. The tommy bar 7 is inserted into a hole through the enlarged head of the screw
and when this is turned, the screw will move up or down, thereby raising or lowering the load.
Exercise
Assemble all parts of the screw jack, shown in Fig. 18.51 and draw the following views:
(i) Half sectional view from the front, and
(ii) View from above.
18.5.14 Pipe Vice
Pipe vices are designed for holding pipes, to facilitate operations such as threading or cutting-off
to required length. Figure 18.52 shows various parts of a pipe vice. To assemble the vice, the
screw rod 4 is screwed into the base 1 from above. When the circular groove at the end of the
screw rod is in-line with the 6 mm diameter transverse hole in the housing, the movable jaw 2 is
inserted from below. After alignment, two set screws 3 are inserted into the jaw. This arrangement
allows the jaw to move vertically without rotation when the handle is operated and the screw is
turning.
The V-shaped base of the housing can accommodate pipes of different diameters. The
serrations provided on the V-shaped end of the movable jaw provide effective grip on the pipe
surface.
Exercise
The details of a pipe vice are shown in Fig. 18.52. Assemble the parts and draw, (i) view from the
front, (ii) sectional view from the left and (iii) view from above.
18.5.15 Speed Reducer
Figure 18.53 shows the various parts of a speed reducer, using worm and worm wheel, which
reduces the speed in a single step. It is used for large ratio of speed reduction and it is of the right
angle drive type. However, when the speed is reduced in two stages, parallel shaft operation is
possible.
The worm shaft 2 is placed in the housing 1 by introducing it through one end of the
housing. The ball bearings 9 are fitted on either side of the worm shaft along with the oil seal 10.
